The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) t... more The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type str...
a8 subunits of a-bungarotoxin-sensitive chick neuronal nicotinic acetyicholine receptors expresse... more a8 subunits of a-bungarotoxin-sensitive chick neuronal nicotinic acetyicholine receptors expressed in Xenopus oocytes from cRNA are shown to form homomenc, acetylcholine-gated, rapidly desensitizing, inwardly rectifying, Ca2-permeable cation chan-nels similar to those of a7 homomers. a8 forms oligomers of several sizes, of which <1 4 % are expressed on the oocyte surface, which is less efficient than for a7 homomers. a8 ho-momers are more sensitive to agonists but less sensitive to antagonists than are a7 homomers, and some agonists for a8 homomers are partial agonists or antagonists for a7 homomers. The pharmacological properties of homomers of a8 and a7 subunits generally reflect those of native a8 and a7 receptors. Two cDNAs for subunits of neuronal nicotinic AChRS that bind aBgt were initially isolated from a chick brain library by Schoepfer et at. (1) and termed aBgt-binding protein subunits
Journal of Pharmacology and Experimental Therapeutics, 1998
We identified regions within the N-terminal extracellular domain of alpha7 nicotinic acetylcholin... more We identified regions within the N-terminal extracellular domain of alpha7 nicotinic acetylcholine receptors that affect channel gating. By single-channel analysis of alpha7 nicotinic acetylcholine receptors currents, we show that the difference in efficacy between the two agonists acetylcholine and 1,1-dimethyl-4-phenylpiperazinium (DMPP) is due to a slower channel activation rate by DMPP. The partial efficacy of DMPP was not caused by channel block or faster desensitization of alpha7 AChRs by DMPP. In addition, the efficacy and, by inference, the activation rate were found to be voltage dependent. Using chimeras of the two closely related subunits alpha7 and alpha8, we map residues that affect channel activation rate and agonist affinity to two different regions of the extracellular domain. Residues that affect channel activation rate are within the sequence 1-179, whereas residues that affect agonist affinity are within the sequence 180-208.
The alpha-bungarotoxin-binding acetylcholine receptors from the human neuroblastoma cell line SH-... more The alpha-bungarotoxin-binding acetylcholine receptors from the human neuroblastoma cell line SH-SY5Y were found to cross-react with some monoclonal antibodies to alpha 7 subunits of nicotinic acetylcholine receptors from chicken brain. The human alpha 7 subunit cDNA from SH-SY5Y was cloned, revealing 94% amino acid sequence identity to rat alpha 7 subunits and 92% identity to chicken alpha 7 subunits. Native human alpha 7 receptors showed affinities for some ligands similar to those previously observed with native chicken alpha 7 receptors, but for other ligands there were large species-specific differences in binding affinity. These results paralleled properties of alpha 7 homomers expressed in Xenopus oocytes. Human alpha 7 homomers exhibited rapidly desensitizing, inwardly rectifying, agonist-induced, cation currents that triggered Ca(2+)-sensitive Cl- channels in the oocytes. A change in efficacy from partial agonist for chicken alpha 7 homomers to full agonist for human alpha ...
Chronic nicotine exposure in tobacco smokers or experimental animals is known to cause an increas... more Chronic nicotine exposure in tobacco smokers or experimental animals is known to cause an increase in brain binding sites for nicotine. It has been proposed that this is an adaptive response of neurons to accumulation of chronically desensitized receptors. Acetylcholine receptors of the same (alpha 4)2(beta 2)3 subunit composition as the predominant subtype of brain nicotinic receptors with high affinity for nicotine have been expressed in Xenopus oocytes and in a permanently transfected fibroblast cell line. Chronic exposure of these cells to nicotine or another agonist is shown to result in an increase in receptor amount, indicating that nicotine-induced up-regulation reflects properties of the alpha 4 beta 2 receptor protein, rather than being an adaptive response unique to the neurons in which these receptors are normally expressed. The nicotine concentration dependence, time course, and extent of receptor up-regulation are similar to those reported for receptors in brain. Up-re...
The Journal of pharmacology and experimental therapeutics, 1997
Because chronic exposure to nicotine and nicotinic drugs might both activate and desensitize nico... more Because chronic exposure to nicotine and nicotinic drugs might both activate and desensitize nicotinic acetylcholine receptors (AChRs), we sought to determine whether prolonged exposure to nicotine concentrations encountered in tobacco users differentially affects electrophysiological properties of major subtypes of human neuronal nicotinic AChRs. Xenopus laevis oocytes were injected with subunit cRNAs encoding (1) homomeric alpha7 AChRs, (2) heteromeric alpha4beta2 AChRs and (3) heteromeric alpha3 AChRs formed from combinations of alpha3, beta2, beta4 and alpha5 cRNAs. Acute activation required micromolar concentrations of nicotine. Chronic exposure to submicromolar concentrations of nicotine irreversibly inactivated many alpha4beta2 AChRs and alpha7 AChRs but inhibited alpha3 AChRs much less. Thus, although alpha3 AChRs are present in the brain in much smaller amounts than are alpha4beta2 AChRs or alpha7 AChRs, alpha3 AChRs in brain and autonomic ganglia may be able to play a rela...
The Journal of pharmacology and experimental therapeutics, 1994
Intracellular recordings were made to study the actions of ATP and related nucleotides on neurons... more Intracellular recordings were made to study the actions of ATP and related nucleotides on neurons from the guinea pig submucous plexus. Local application of ATP, by pressure, induced a depolarization in most AH-type neurons, which had a latency of several milliseconds, lasted for about 5 sec, appeared to reverse at about +4 mV and occurred concomitantly with a reduction in input resistance. Pressure application of ATP also depolarized the S-type neurons. In most of these cells the depolarization had two phases: the first component resembled the depolarization observed in AH cells and the second component was much slower in onset and was longer lasting (30-90 sec). The slower component was associated with an increase in input resistance, reversed polarity near the potassium equilibrium potential and was observed in isolation in 30% of S neurons. Superfusion of ATP or other analogs (0.03-10 microns) induced a slow depolarization in most of S neurons with the following rank order of po...
The Journal of pharmacology and experimental therapeutics, 1998
Functional effects of human alpha 5 nicotinic ACh receptor (AChR) subunits coassembled with alpha... more Functional effects of human alpha 5 nicotinic ACh receptor (AChR) subunits coassembled with alpha 3 and beta 2 or with alpha 3 and beta 4 subunits, were investigated in Xenopus oocytes. The presence of alpha 5 subunits altered some properties of both alpha 3 AChRs and differentially altered other properties of alpha 3 beta 2 AChRs vs. alpha 3 beta 4 AChRs. alpha 5 subunits increased desensitization and Ca++ permeability of all alpha 3 AChRs. The Ca++ permeabilities of both alpha 3 beta 2 alpha 5 and alpha 3 beta 4 alpha 5 AChRs were comparable to that of alpha 7 AChRs. As we have shown previously, alpha 5 subunits increased the ACh sensitivity of alpha 3 beta 2 AChRs 50-fold but had little effect on alpha 3 beta 4 AChRs. alpha 5 caused only subtle changes in the activation potencies of alpha 3 AChRs for nicotine, cytisine and 1,1-dimethyl-4-plenylpiperazinium (DMPP). However, alpha 5 increased the efficacies of nicotine and DMPP on alpha 3 beta 2 AChRs but decreased them on alpha 3 ...
Pharmacological properties of the (+)- and (-)-isomers of synthetic epibatidine, exo-2-(6-chloro-... more Pharmacological properties of the (+)- and (-)-isomers of synthetic epibatidine, exo-2-(6-chloro-3-pyridyl)-7-azabicyclo-[2.2.1]heptane, were compared with nicotine and acetylcholine on several subtypes of chicken and human nicotinic acetylcholine receptors (AChRs). Both isomers of epibatidine behaved as extremely potent full agonists on chicken (alpha 3 beta 2, alpha 3 beta 4, alpha 4 beta 2, alpha 7, and alpha 8) and human (alpha 3 beta 2, alpha 3 beta 4, and alpha 7) neuronal AChRs expressed in Xenopus oocytes. Currents induced by epibatidine were effectively blocked by the nicotinic antagonists hexamethonium and mecamylamine. Apparent affinity was 100 to 1000-fold higher for epibatidine than for nicotine or acetylcholine. EC50 values ranged from 1 nM (for homomeric chicken alpha 8) to 2 microM (for homomeric chicken alpha 7). Epibatidine showed comparatively lower affinity for muscle-type AChRs from Torpedo and humans (EC50 values, 1.6 and 16 microM respectively). In binding ass...
alpha 8 subunits of alpha-bungarotoxin-sensitive chick neuronal nicotinic acetylcholine receptors... more alpha 8 subunits of alpha-bungarotoxin-sensitive chick neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes from cRNA are shown to form homomeric, acetylcholine-gated, rapidly desensitizing, inwardly rectifying, Ca(2+)-permeable cation channels similar to those of alpha 7 homomers. alpha 8 forms oligomers of several sizes, of which < 14% are expressed on the oocyte surface, which is less efficient than for alpha 7 homomers. alpha 8 homomers are more sensitive to agonists but less sensitive to antagonists than are alpha 7 homomers, and some agonists for alpha 8 homomers are partial agonists or antagonists for alpha 7 homomers. The pharmacological properties of homomers of alpha 8 and alpha 7 subunits generally reflect those of native alpha 8 and alpha 7 receptors.
An important but poorly understood feature of traumatic brain injury (TBI) is the clinically seri... more An important but poorly understood feature of traumatic brain injury (TBI) is the clinically serious problem of spatiotemporal progression (blossoming) of a hemorrhagic contusion, a phenomenon we term progressive secondary hemorrhage (PSH). Molecular ...
Fiziologicheskiĭ zhurnal SSSR imeni I. M. Sechenova, 1984
The electrical potentials recorded from human forearm were stored and averaged as synchronous wit... more The electrical potentials recorded from human forearm were stored and averaged as synchronous with the cardiac rhythm. The R-wave of the ECG was used to synchronize the averaging system. The record obtained with this technique from human forearm during transient stop of blood flow to avoid mechanical artifacts was a sinusoid-like curve with peaks between the R-waves of the ECG. The nature of this electronegative wave was investigated by means of comparing electrograms and rheograms recorded from forearm of normal subjects and subjects after denervation or desympathization of their upper extremities. The data obtained suggest that the electronegative wave recorded with this technique is the averaged sum of tonic pulse-synchronous electrical activity of sympathetic nerve's fibers innervating vasoconstrictors of the skeletal muscle.
Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes pl... more Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes placed on the surface of the human arm or using the rabbit hindlimb. The signal-to-noise ratio has been improved using record averaging synchronized with the ECG. The recorded activity in man is a slow negative wave of sinusoid-like shape with a mean peak amplitude 0.08 +/- 0.03 microV. The sympathetic origin of this activity is suggested by the facts that its time course and conduction velocity are similar to those of integrated spontaneous electrical activity, recorded directly from postganglionic sympathetic fibers in the rabbit, and that it can be recorded from skin surface as a response to direct electrical stimulation of sympathetic nerve in the same animal.
Cellular Ca(2+) signaling underlies diverse vital biological processes, including muscle contract... more Cellular Ca(2+) signaling underlies diverse vital biological processes, including muscle contractility, memory encoding, fertilization, cell survival, and cell death. Despite extensive studies, the fundamental control mechanisms that regulate intracellular Ca(2+) movement remain enigmatic. We have found recently that activation of the (Na(+)+K(+))-ATPase markedly potentiates intracellular Ca(2+) transients and contractility of rat heart cells. Little is known about the pathway responsible for the activation of the (Na(+)+K(+))-ATPase-initiated Ca(2+) signaling. Here, we demonstrate a novel mechanism in which activation of the (Na(+)+K(+))-ATPase is coupled to increased L-type Ca(2+) channel function through a signaling cascade involving Src and ERK1/2 but not well established regulators of the channel, such as adrenergic receptor system or activation of PKA or CaMKII. We have also identified Ser(1928), a phosphorylation site for the alpha1 subunit of the L-type Ca(2+) channel that may participate in the activation of the (Na(+)+K(+))-ATPase-mediated Ca(2+) signaling. The findings reported here uncover a novel molecular cross-talk between activation of the (Na(+)+K(+))-ATPase and L-type Ca(2+) channel and provide new insights into Ca(2+) signaling mechanisms for deeper understanding of the nature of cellular Ca(2+) handling in heart.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997
A mutation (S247F) in the channel-lining domain (M2) of the alpha4 nicotinic acetylcholine recept... more A mutation (S247F) in the channel-lining domain (M2) of the alpha4 nicotinic acetylcholine receptor (AChR) subunit has previously been linked genetically to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). To better understand the functional significance of this mutation, we characterized the properties of mutant and wild-type human alpha4beta2 AChRs expressed in Xenopus oocytes. Both had similar expression levels and EC50 values for ACh and nicotine. Substantial use-dependent functional upregulation was found for mutant alpha4beta2 AChRs, but not for wild type. Mutant AChR responses showed faster desensitization, slower recovery from desensitization, less inward rectification, and virtually no Ca2+ permeability as compared with wild-type alpha4beta2 AChRs. Addition of the alpha5 subunit restored Ca2+ permeability to the mutant alpha4beta2alpha5 AChRs. At -80 mV, wild-type alpha4beta2 AChR single channel currents exhibited two conductances, each with two mean open times ...
The Journal of pharmacology and experimental therapeutics, 1998
3-(2,4-dimethoxybenzylidene)anabaseine (GTS-21) is a selective partial agonist for rat alpha-7 ni... more 3-(2,4-dimethoxybenzylidene)anabaseine (GTS-21) is a selective partial agonist for rat alpha-7 nicotine receptors with reportedly much lower efficacy for human alpha-7 receptors. Because this drug improves memory-related performance in nonhuman primates, and is presently in a clinical trial for Alzheimer's disease, we investigated the potential effects of its primary human metabolite, 3-(4-hydroxy, 2-methoxy-benzylidene)anabaseine) on human as well as rat nicotinic acetylcholine receptor. 4OH-GTS-21 exhibited a similar level of efficacy for both rat and human alpha-7 receptors expressed in Xenopus oocytes. It displaced high affinity [125I]alpha-bungarotoxin binding to human SK-N-SH cell-membranes (Ki 0.17 microM) and rat PC12 cell-membranes (Ki 0.45 microM). GTS-21 also displaced [125I]alpha-bungarotoxin binding to PC12 cell membranes with high potency (Ki 0.31 microM), but was much less potent in this regard in SK-N-SH cells (23 microM). 4OH-GTS-21 produced less residual inhibi...
The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) t... more The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type str...
a8 subunits of a-bungarotoxin-sensitive chick neuronal nicotinic acetyicholine receptors expresse... more a8 subunits of a-bungarotoxin-sensitive chick neuronal nicotinic acetyicholine receptors expressed in Xenopus oocytes from cRNA are shown to form homomenc, acetylcholine-gated, rapidly desensitizing, inwardly rectifying, Ca2-permeable cation chan-nels similar to those of a7 homomers. a8 forms oligomers of several sizes, of which <1 4 % are expressed on the oocyte surface, which is less efficient than for a7 homomers. a8 ho-momers are more sensitive to agonists but less sensitive to antagonists than are a7 homomers, and some agonists for a8 homomers are partial agonists or antagonists for a7 homomers. The pharmacological properties of homomers of a8 and a7 subunits generally reflect those of native a8 and a7 receptors. Two cDNAs for subunits of neuronal nicotinic AChRS that bind aBgt were initially isolated from a chick brain library by Schoepfer et at. (1) and termed aBgt-binding protein subunits
Journal of Pharmacology and Experimental Therapeutics, 1998
We identified regions within the N-terminal extracellular domain of alpha7 nicotinic acetylcholin... more We identified regions within the N-terminal extracellular domain of alpha7 nicotinic acetylcholine receptors that affect channel gating. By single-channel analysis of alpha7 nicotinic acetylcholine receptors currents, we show that the difference in efficacy between the two agonists acetylcholine and 1,1-dimethyl-4-phenylpiperazinium (DMPP) is due to a slower channel activation rate by DMPP. The partial efficacy of DMPP was not caused by channel block or faster desensitization of alpha7 AChRs by DMPP. In addition, the efficacy and, by inference, the activation rate were found to be voltage dependent. Using chimeras of the two closely related subunits alpha7 and alpha8, we map residues that affect channel activation rate and agonist affinity to two different regions of the extracellular domain. Residues that affect channel activation rate are within the sequence 1-179, whereas residues that affect agonist affinity are within the sequence 180-208.
The alpha-bungarotoxin-binding acetylcholine receptors from the human neuroblastoma cell line SH-... more The alpha-bungarotoxin-binding acetylcholine receptors from the human neuroblastoma cell line SH-SY5Y were found to cross-react with some monoclonal antibodies to alpha 7 subunits of nicotinic acetylcholine receptors from chicken brain. The human alpha 7 subunit cDNA from SH-SY5Y was cloned, revealing 94% amino acid sequence identity to rat alpha 7 subunits and 92% identity to chicken alpha 7 subunits. Native human alpha 7 receptors showed affinities for some ligands similar to those previously observed with native chicken alpha 7 receptors, but for other ligands there were large species-specific differences in binding affinity. These results paralleled properties of alpha 7 homomers expressed in Xenopus oocytes. Human alpha 7 homomers exhibited rapidly desensitizing, inwardly rectifying, agonist-induced, cation currents that triggered Ca(2+)-sensitive Cl- channels in the oocytes. A change in efficacy from partial agonist for chicken alpha 7 homomers to full agonist for human alpha ...
Chronic nicotine exposure in tobacco smokers or experimental animals is known to cause an increas... more Chronic nicotine exposure in tobacco smokers or experimental animals is known to cause an increase in brain binding sites for nicotine. It has been proposed that this is an adaptive response of neurons to accumulation of chronically desensitized receptors. Acetylcholine receptors of the same (alpha 4)2(beta 2)3 subunit composition as the predominant subtype of brain nicotinic receptors with high affinity for nicotine have been expressed in Xenopus oocytes and in a permanently transfected fibroblast cell line. Chronic exposure of these cells to nicotine or another agonist is shown to result in an increase in receptor amount, indicating that nicotine-induced up-regulation reflects properties of the alpha 4 beta 2 receptor protein, rather than being an adaptive response unique to the neurons in which these receptors are normally expressed. The nicotine concentration dependence, time course, and extent of receptor up-regulation are similar to those reported for receptors in brain. Up-re...
The Journal of pharmacology and experimental therapeutics, 1997
Because chronic exposure to nicotine and nicotinic drugs might both activate and desensitize nico... more Because chronic exposure to nicotine and nicotinic drugs might both activate and desensitize nicotinic acetylcholine receptors (AChRs), we sought to determine whether prolonged exposure to nicotine concentrations encountered in tobacco users differentially affects electrophysiological properties of major subtypes of human neuronal nicotinic AChRs. Xenopus laevis oocytes were injected with subunit cRNAs encoding (1) homomeric alpha7 AChRs, (2) heteromeric alpha4beta2 AChRs and (3) heteromeric alpha3 AChRs formed from combinations of alpha3, beta2, beta4 and alpha5 cRNAs. Acute activation required micromolar concentrations of nicotine. Chronic exposure to submicromolar concentrations of nicotine irreversibly inactivated many alpha4beta2 AChRs and alpha7 AChRs but inhibited alpha3 AChRs much less. Thus, although alpha3 AChRs are present in the brain in much smaller amounts than are alpha4beta2 AChRs or alpha7 AChRs, alpha3 AChRs in brain and autonomic ganglia may be able to play a rela...
The Journal of pharmacology and experimental therapeutics, 1994
Intracellular recordings were made to study the actions of ATP and related nucleotides on neurons... more Intracellular recordings were made to study the actions of ATP and related nucleotides on neurons from the guinea pig submucous plexus. Local application of ATP, by pressure, induced a depolarization in most AH-type neurons, which had a latency of several milliseconds, lasted for about 5 sec, appeared to reverse at about +4 mV and occurred concomitantly with a reduction in input resistance. Pressure application of ATP also depolarized the S-type neurons. In most of these cells the depolarization had two phases: the first component resembled the depolarization observed in AH cells and the second component was much slower in onset and was longer lasting (30-90 sec). The slower component was associated with an increase in input resistance, reversed polarity near the potassium equilibrium potential and was observed in isolation in 30% of S neurons. Superfusion of ATP or other analogs (0.03-10 microns) induced a slow depolarization in most of S neurons with the following rank order of po...
The Journal of pharmacology and experimental therapeutics, 1998
Functional effects of human alpha 5 nicotinic ACh receptor (AChR) subunits coassembled with alpha... more Functional effects of human alpha 5 nicotinic ACh receptor (AChR) subunits coassembled with alpha 3 and beta 2 or with alpha 3 and beta 4 subunits, were investigated in Xenopus oocytes. The presence of alpha 5 subunits altered some properties of both alpha 3 AChRs and differentially altered other properties of alpha 3 beta 2 AChRs vs. alpha 3 beta 4 AChRs. alpha 5 subunits increased desensitization and Ca++ permeability of all alpha 3 AChRs. The Ca++ permeabilities of both alpha 3 beta 2 alpha 5 and alpha 3 beta 4 alpha 5 AChRs were comparable to that of alpha 7 AChRs. As we have shown previously, alpha 5 subunits increased the ACh sensitivity of alpha 3 beta 2 AChRs 50-fold but had little effect on alpha 3 beta 4 AChRs. alpha 5 caused only subtle changes in the activation potencies of alpha 3 AChRs for nicotine, cytisine and 1,1-dimethyl-4-plenylpiperazinium (DMPP). However, alpha 5 increased the efficacies of nicotine and DMPP on alpha 3 beta 2 AChRs but decreased them on alpha 3 ...
Pharmacological properties of the (+)- and (-)-isomers of synthetic epibatidine, exo-2-(6-chloro-... more Pharmacological properties of the (+)- and (-)-isomers of synthetic epibatidine, exo-2-(6-chloro-3-pyridyl)-7-azabicyclo-[2.2.1]heptane, were compared with nicotine and acetylcholine on several subtypes of chicken and human nicotinic acetylcholine receptors (AChRs). Both isomers of epibatidine behaved as extremely potent full agonists on chicken (alpha 3 beta 2, alpha 3 beta 4, alpha 4 beta 2, alpha 7, and alpha 8) and human (alpha 3 beta 2, alpha 3 beta 4, and alpha 7) neuronal AChRs expressed in Xenopus oocytes. Currents induced by epibatidine were effectively blocked by the nicotinic antagonists hexamethonium and mecamylamine. Apparent affinity was 100 to 1000-fold higher for epibatidine than for nicotine or acetylcholine. EC50 values ranged from 1 nM (for homomeric chicken alpha 8) to 2 microM (for homomeric chicken alpha 7). Epibatidine showed comparatively lower affinity for muscle-type AChRs from Torpedo and humans (EC50 values, 1.6 and 16 microM respectively). In binding ass...
alpha 8 subunits of alpha-bungarotoxin-sensitive chick neuronal nicotinic acetylcholine receptors... more alpha 8 subunits of alpha-bungarotoxin-sensitive chick neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes from cRNA are shown to form homomeric, acetylcholine-gated, rapidly desensitizing, inwardly rectifying, Ca(2+)-permeable cation channels similar to those of alpha 7 homomers. alpha 8 forms oligomers of several sizes, of which < 14% are expressed on the oocyte surface, which is less efficient than for alpha 7 homomers. alpha 8 homomers are more sensitive to agonists but less sensitive to antagonists than are alpha 7 homomers, and some agonists for alpha 8 homomers are partial agonists or antagonists for alpha 7 homomers. The pharmacological properties of homomers of alpha 8 and alpha 7 subunits generally reflect those of native alpha 8 and alpha 7 receptors.
An important but poorly understood feature of traumatic brain injury (TBI) is the clinically seri... more An important but poorly understood feature of traumatic brain injury (TBI) is the clinically serious problem of spatiotemporal progression (blossoming) of a hemorrhagic contusion, a phenomenon we term progressive secondary hemorrhage (PSH). Molecular ...
Fiziologicheskiĭ zhurnal SSSR imeni I. M. Sechenova, 1984
The electrical potentials recorded from human forearm were stored and averaged as synchronous wit... more The electrical potentials recorded from human forearm were stored and averaged as synchronous with the cardiac rhythm. The R-wave of the ECG was used to synchronize the averaging system. The record obtained with this technique from human forearm during transient stop of blood flow to avoid mechanical artifacts was a sinusoid-like curve with peaks between the R-waves of the ECG. The nature of this electronegative wave was investigated by means of comparing electrograms and rheograms recorded from forearm of normal subjects and subjects after denervation or desympathization of their upper extremities. The data obtained suggest that the electronegative wave recorded with this technique is the averaged sum of tonic pulse-synchronous electrical activity of sympathetic nerve's fibers innervating vasoconstrictors of the skeletal muscle.
Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes pl... more Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes placed on the surface of the human arm or using the rabbit hindlimb. The signal-to-noise ratio has been improved using record averaging synchronized with the ECG. The recorded activity in man is a slow negative wave of sinusoid-like shape with a mean peak amplitude 0.08 +/- 0.03 microV. The sympathetic origin of this activity is suggested by the facts that its time course and conduction velocity are similar to those of integrated spontaneous electrical activity, recorded directly from postganglionic sympathetic fibers in the rabbit, and that it can be recorded from skin surface as a response to direct electrical stimulation of sympathetic nerve in the same animal.
Cellular Ca(2+) signaling underlies diverse vital biological processes, including muscle contract... more Cellular Ca(2+) signaling underlies diverse vital biological processes, including muscle contractility, memory encoding, fertilization, cell survival, and cell death. Despite extensive studies, the fundamental control mechanisms that regulate intracellular Ca(2+) movement remain enigmatic. We have found recently that activation of the (Na(+)+K(+))-ATPase markedly potentiates intracellular Ca(2+) transients and contractility of rat heart cells. Little is known about the pathway responsible for the activation of the (Na(+)+K(+))-ATPase-initiated Ca(2+) signaling. Here, we demonstrate a novel mechanism in which activation of the (Na(+)+K(+))-ATPase is coupled to increased L-type Ca(2+) channel function through a signaling cascade involving Src and ERK1/2 but not well established regulators of the channel, such as adrenergic receptor system or activation of PKA or CaMKII. We have also identified Ser(1928), a phosphorylation site for the alpha1 subunit of the L-type Ca(2+) channel that may participate in the activation of the (Na(+)+K(+))-ATPase-mediated Ca(2+) signaling. The findings reported here uncover a novel molecular cross-talk between activation of the (Na(+)+K(+))-ATPase and L-type Ca(2+) channel and provide new insights into Ca(2+) signaling mechanisms for deeper understanding of the nature of cellular Ca(2+) handling in heart.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1997
A mutation (S247F) in the channel-lining domain (M2) of the alpha4 nicotinic acetylcholine recept... more A mutation (S247F) in the channel-lining domain (M2) of the alpha4 nicotinic acetylcholine receptor (AChR) subunit has previously been linked genetically to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). To better understand the functional significance of this mutation, we characterized the properties of mutant and wild-type human alpha4beta2 AChRs expressed in Xenopus oocytes. Both had similar expression levels and EC50 values for ACh and nicotine. Substantial use-dependent functional upregulation was found for mutant alpha4beta2 AChRs, but not for wild type. Mutant AChR responses showed faster desensitization, slower recovery from desensitization, less inward rectification, and virtually no Ca2+ permeability as compared with wild-type alpha4beta2 AChRs. Addition of the alpha5 subunit restored Ca2+ permeability to the mutant alpha4beta2alpha5 AChRs. At -80 mV, wild-type alpha4beta2 AChR single channel currents exhibited two conductances, each with two mean open times ...
The Journal of pharmacology and experimental therapeutics, 1998
3-(2,4-dimethoxybenzylidene)anabaseine (GTS-21) is a selective partial agonist for rat alpha-7 ni... more 3-(2,4-dimethoxybenzylidene)anabaseine (GTS-21) is a selective partial agonist for rat alpha-7 nicotine receptors with reportedly much lower efficacy for human alpha-7 receptors. Because this drug improves memory-related performance in nonhuman primates, and is presently in a clinical trial for Alzheimer's disease, we investigated the potential effects of its primary human metabolite, 3-(4-hydroxy, 2-methoxy-benzylidene)anabaseine) on human as well as rat nicotinic acetylcholine receptor. 4OH-GTS-21 exhibited a similar level of efficacy for both rat and human alpha-7 receptors expressed in Xenopus oocytes. It displaced high affinity [125I]alpha-bungarotoxin binding to human SK-N-SH cell-membranes (Ki 0.17 microM) and rat PC12 cell-membranes (Ki 0.45 microM). GTS-21 also displaced [125I]alpha-bungarotoxin binding to PC12 cell membranes with high potency (Ki 0.31 microM), but was much less potent in this regard in SK-N-SH cells (23 microM). 4OH-GTS-21 produced less residual inhibi...
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Papers by V. Gerzanich