Slow excitatory postsynaptic potentials in sympathetic ganglia often involve suppression of a voltage-dependent potassium current termed the M current. This current is suppressed by the muscarinic action of acetylcholine, by peptides such... more
Slow excitatory postsynaptic potentials in sympathetic ganglia often involve suppression of a voltage-dependent potassium current termed the M current. This current is suppressed by the muscarinic action of acetylcholine, by peptides such as luteinizing hormone releasing hormone, and sometimes by α-adrenoceptor agonists. Activation of β-adrenoceptors sometimes produces weak potentiation. The voltage dependence of the M current is such that its suppression increases the excitability of ganglionic neurones. Since this sometimes leads to spontaneous discharge, activation of the slow excitatory postsynaptic potential mechanism (or modulation of M current) within a sympathetic ganglion produces effects that manifest in the autonomic outflow to the target organ. In frogs, M currents are present in the neurones of both paravertebral sympathetic ganglia and cardiac parasympathetic ganglia. Since the M current is suppressed by adrenaline in the parasympathetic ganglia and these ganglia often...
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The food dye erythrosin B has been reported to inhibit the neuronal uptake of catecholamines. To test this hypothesis we examined the effect of the dye on the responses of neurons in amphibian sympathetic ganglia to both dopamine and... more
The food dye erythrosin B has been reported to inhibit the neuronal uptake of catecholamines. To test this hypothesis we examined the effect of the dye on the responses of neurons in amphibian sympathetic ganglia to both dopamine and epinephrine. Although the hyperpolarizations induced by both catecholamines were potentiated by the conventional uptake blocker, desipramine (0.5 microM), low doses of erythrosin B (1-10 microM) produced an irreversible blockade. It was therefore not possible to evaluate the hypothesis that the dye might block catecholamine uptake. Xanthine dyes such as erythrosin B have also been reported to inhibit Na-K-adenosine triphosphatase. In agreement with this possibility we found that erythrosin B promoted irreversible inhibition of the (nicotinic) acetylcholine after-hyperpolarization. This response is generated by the electrogenic activity of the Na+ pump. Neither this Na+ pump inhibition nor erythrosin-induced membrane hyperpolarization appeared to account for the effect of the dye on catecholamine responses. The irreversible antagonism of epinephrine and dopamine by erythrosin was specific in that hyperpolarizing responses to muscarinic antagonists such as methacholine were relatively insensitive to the dye. It is therefore concluded that erythrosin B selectively antagonizes responses to catecholamines in amphibian sympathetic ganglia. No information as to the exact molecular mechanism of this antagonism is available from the present experiments.
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The adrenaline-induced hyperpolarization (AdH) and the responses evoked by muscarine and luteinizing hormone releasing hormone (LHRH) were recorded from neurones in amphibian sympathetic ganglia by means of the sucrose gap technique. The... more
The adrenaline-induced hyperpolarization (AdH) and the responses evoked by muscarine and luteinizing hormone releasing hormone (LHRH) were recorded from neurones in amphibian sympathetic ganglia by means of the sucrose gap technique. The amplitude of the AdH was reduced when 'M-channel' closure was promoted by superfusion of LHRH or muscarine. 4-Aminopyridine (4-AP, 1 mM) antagonized the AdH, but not the depolarization evoked by muscarinic agonists. This implies that the channels involved in the electrogenesis of the AdH have different pharmacological properties from 'M-channels' and that the AdH is not generated by the opening of 'M-channels' outside their normal voltage range. Possible explanations for the attenuation of the AdH by muscarine and LHRH might be that (i) intracellular biochemical changes produced by these substances somehow interfere with the generation of the AdH or that (ii) muscarine and LHRH have allosteric interactions with the adrenoceptor mediating the AdH.
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ABSTRACT
ABSTRACT
The pontine parabrachial nucleus (PBN) receives both opioid and Neuropeptide FF (NPFF) projections from the lower brain stem and/or the spinal cord. Because of this anatomical convergence and previous evidence that NPFF displays both pro-... more
The pontine parabrachial nucleus (PBN) receives both opioid and Neuropeptide FF (NPFF) projections from the lower brain stem and/or the spinal cord. Because of this anatomical convergence and previous evidence that NPFF displays both pro- and anti-opioid activities, this study examined the synaptic effects of NPFF in the PBN and the mechanisms underlying these effects using an in vitro brain slice preparation and the nystatin-perforated patch-clamp recording technique. Under voltage-clamp conditions, NPFF reversibly reduced the evoked excitatory postsynaptic currents (EPSCs) in a dose-dependent fashion. This effect was not accompanied by apparent changes in the holding current, the current-voltage relationship or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced inward currents in the PBN cells. When a paired-pulse protocol was used, NPFF increased the ratio of these synaptic currents. Analysis of miniature EPSCs showed that NPFF caused a rightward shift in the freque...
Research Interests: Neurophysiology, Patch-clamp and imaging techniques, Animals, Male, Peptides, and 11 morePotassium, Rats, Tetrodotoxin, Naloxone, Electric Conductivity, Ligands, 4-Tetrahydroisoquinolines, Excitatory Postsynaptic Potentials, Psychology and Cognitive Sciences, Medical and Health Sciences, and In Vitro Techniques
The present study examined the electrophysiological and kinetic properties of a hyperpolarizing-activated current in neurons located in the lateral parabrachial nucleus. We investigated whether differences observed in the shape of action... more
The present study examined the electrophysiological and kinetic properties of a hyperpolarizing-activated current in neurons located in the lateral parabrachial nucleus. We investigated whether differences observed in the shape of action potential afterhyperpolarizations in lateral parabrachial nucleus neurons, and the ability of these neurons to accommodate, correlated with the presence of this current. A voltage-activated inwardly rectifying current that increased in amplitude with hyperpolarization was observed in 83% of the neurons examined. Under voltage-clamp recording conditions, this current activated at about -70 mV, was half-activated at -96.5 mV and was blocked by bath application of 2 mM cesium, but not by 100 microM barium. In the current-clamp mode, activation of this current resulted in a transient increase in neuronal excitability at the termination of the more negative current injections. The presence of this current did not correlate with specific action potential ...
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1. Neurones dissociated from Rana pipiens paravertebral sympathetic ganglia were studied by means of the whole-cell patch-clamp technique. Responses to agonists were best recorded when cyclic AMP was included in the patch pipette. 2. Two... more
1. Neurones dissociated from Rana pipiens paravertebral sympathetic ganglia were studied by means of the whole-cell patch-clamp technique. Responses to agonists were best recorded when cyclic AMP was included in the patch pipette. 2. Two populations of cells were identified on the basis of size (input capacitance, Cin) and the presence or absence of a fast, transient outward current (A-current, IA). This current was usually present in the 'large' cells (Cin = 40.5 +/- 1.5 pF, n = 66) but absent from 'small' cells (Cin = 21.0 +/- 0.8 pF, n = 70). 3. Both cell types exhibited a slowly activating, non-inactivating K+ current (M-current, IM) which was suppressed by luteinizing hormone-releasing hormone (LHRH, 10-100 microM). Threshold for activation of IM was about -75 mV, half-maximal activation was at -50 mV and the M-conductance GM increased e-fold for at 7 mV change in membrane potential. The maximum value for IM studied in large cells by patch-clamp procedures was l...
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Although dopamine (DA)-containing neurons participate in a number of important cerebral functions, the physiology of their synaptic connections is poorly understood. By using whole-cell patch-clamp recording in thin slices of rat... more
Although dopamine (DA)-containing neurons participate in a number of important cerebral functions, the physiology of their synaptic connections is poorly understood. By using whole-cell patch-clamp recording in thin slices of rat mesencephalon, we have investigated the biophysical properties of synaptic events and the nature of neurotransmitter(s) and receptors involved in the synaptic input to DA neurons in substantia nigra. The histological and electrophysiological characteristics of these cells were consistent with those described by recent in vivo and in vitro studies, thus allowing their unequivocal identification. Under appropriate experimental conditions, intranigral stimulation produced excitatory synaptic inputs in DA neurons. By voltage-clamp analysis, most of these excitatory postsynaptic currents (EPSCs) had a rise time of about 1.0 msec and a decay phase that could be fit by the sum of two exponential curves so that a fast and a slow component could be distinguished. Th...
Research Interests: Electrophysiology, Dopamine, Evoked Potentials, Animals, Complex network, and 15 moreNeurons, Neuronal Death, Basal ganglia, Drugs of Abuse, Mechanism of action, Mecamylamine, In Vitro Studies, Action Potentials, Glutamate Receptor, NMDA receptor, Mesencephalon, Psychology and Cognitive Sciences, Kynurenic acid, Medical and Health Sciences, and In Vitro Techniques
1. The whole-cell patch-clamp technique was used to record membrane currents from neurones which were acutely dissociated from the intra-atrial parasympathetic ganglia of Rana pipiens. The effects of muscarine and adrenaline were observed... more
1. The whole-cell patch-clamp technique was used to record membrane currents from neurones which were acutely dissociated from the intra-atrial parasympathetic ganglia of Rana pipiens. The effects of muscarine and adrenaline were observed at a holding potential of -30 mV. Extracellular potassium concentration ([K+]o) was 2, 6 or 20 mM. 2. Muscarine (10 microM) produced inward current in thirteen cells, outward current in eighteen cells and seven cells were unaffected. Inward currents were observed in six out of ten neurones in which the intracellular solution contained adenosine triphosphate (ATP; 100 microM) and outward currents were seen in eleven out of fourteen neurones which contained adenosine 3',5'-cyclic monophosphate (cyclic & 100 microM). 3. In five out of nine cells tested, the inward current produced by muscarine was attributable to a 30% depression of a voltage-dependent current which resembled the M-current (IM). Muscarine-induced inward current in the other fo...
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The adrenaline-induced hyperpolarization, which was recorded in neurons of bullfrog paravertebral sympathetic ganglia by means of the sucrose gap technique, was antagonized by 1 mM 4-aminopyridine. The response was unaffected by drugs... more
The adrenaline-induced hyperpolarization, which was recorded in neurons of bullfrog paravertebral sympathetic ganglia by means of the sucrose gap technique, was antagonized by 1 mM 4-aminopyridine. The response was unaffected by drugs which influence intracellular Ca2+ movements or Ca2+-sensitive K+ conductances, i.e. 100 or 200 microM Cd2+, 60 microM dantrolene Na+, 10 mM tetraethylammonium bromide, 0.5-2.0 microM apamin or 70 microM (+)-tubocurarine chloride. The spontaneous, rhythmic hyperpolarizations which occur in ganglionic neurons in the presence of 5 mM caffeine and reflect activation of Ca2+-sensitive K+ conductances following mobilization of intracellular Ca2+, were examined by means of intracellular recording. These responses were often biphasic, comprising a transient rapid early phase and a slow late phase. Tetraethylammonium (10 mM) and 0.5-2.0 microM apamin antagonized the rapid early phase and 70 microM (+)-tubocurarine chloride antagonized both phases of the response. Neither phase of these spontaneous, rhythmic, caffeine-induced hyperpolarizations were affected by 1 mM 4-aminopyridine. Although the adrenaline-induced hyperpolarization was antagonized by 50 microM 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate and by 50 microM quinidine, the majority of the results argue against the hypothesis that mobilization of intracellular Ca2+ is required for activation of the K+ conductance thought to underlie the adrenaline-induced hyperpolarization.
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The potassium-activated hyperpolarization (KH) was used as an index of electrogenic Na+ pumping in bullfrog sympathetic ganglia. This response was evoked by storing ganglia in K-free Ringer's solution and briefly... more
The potassium-activated hyperpolarization (KH) was used as an index of electrogenic Na+ pumping in bullfrog sympathetic ganglia. This response was evoked by storing ganglia in K-free Ringer's solution and briefly introducing normal Ringer's solution containing 2 mM K+ at regular intervals. The apparent EC50 for K+ was 2.21 mM (range 0.88-3.54 mM, for n = 5) and at least 10 mM K+ was required to produce a maximal KH response. Adrenaline, which produces membrane hyperpolarization by increasing K+ conductance (gK), increased the amplitude of KH responses. When the K+ efflux accompanying the adrenaline-induced hyperpolarization (AdH) was blocked with 2 mM Ba2+, the KH was no longer potentiated. It is suggested that the K+ moving out of the cells during the AdH accumulates extracellularly and stimulates the Na+ pump.
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Neuropeptide Y (NPY) is found in the C-cells yet is absent from the B-cells of amphibian sympathetic ganglia. The effects of this peptide on both cell types were studied using the whole-cell patch-clamp recording technique. Although NPY... more
Neuropeptide Y (NPY) is found in the C-cells yet is absent from the B-cells of amphibian sympathetic ganglia. The effects of this peptide on both cell types were studied using the whole-cell patch-clamp recording technique. Although NPY had little effect on the B-cells, it opened inwardly-rectifying K(+)-channels in C-cells. This effect of the peptide on C-cell K(+)-channels was similar to that produced by muscarine and adrenaline and may be related to autoreceptor function.
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Carotenoids are an important group of phytonutrients that are abundant in fruits and vegetables. Epidemiological and clinical intervention studies have implied the presence of protective qualities of these nutrients against the... more
Carotenoids are an important group of phytonutrients that are abundant in fruits and vegetables. Epidemiological and clinical intervention studies have implied the presence of protective qualities of these nutrients against the development of a variety of chronic diseases. Previously, human carotenoid status has been assessed in serum and tissue using high-performance liquid chromatography (HPLC) methodology. Recently, a Raman spectroscopy (RS)-based photonic method has been developed to accurately and noninvasively measure the carotenoid concentration in human skin. (1) To validate skin RS methodology against standard serum carotenoid measurements by HPLC and (2) to establish and compare the reliability of the 2 methods. This study included 372 healthy adults who provided 3 blood samples and 3 RS skin carotenoid measurements within an 8-day period; each day-matched blood sample and RS determination was spaced by >or=48 hours. Consistent positive correlations were observed for each of 3 separate same-day correlation plots of total serum versus RS skin carotenoids. Overall estimate of the line of best fit from analysis of covariance, using all 3 samples (n = 1116), yielded a Pearson correlation of R = 0.81 (r(2) = 0.66; p < 0.001). Based on analysis of variance, RS skin carotenoid methodology exhibited 0.9% less variance over the 3 tests than serum carotenoids by the HPLC method (p < 0.03). RS accurately measures total carotenoids in human skin with less intra-individual variability than measurement of serum carotenoids by HPLC analysis. RS technology is a valid and reliable noninvasive method to rapidly assess carotenoid nutritional status in humans.
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Research Interests: Cognitive Science, Electrophysiology, Prefrontal Cortex, Glucose, Animals, and 15 morePlant tissue Culture Techniques, Male, Brain Ischemia, Synaptic Transmission, Neurons, Rats, Oxygen, Culture Media, Statistical Methods for Neuroscience, Cell Survival, Neurosciences, Antipyrine, Neuroprotective Agents, Excitatory Postsynaptic Potentials, and Neuroscience Methods
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The pontine parabrachial nucleus (PBN) is a major recipient of a diverse array of autonomic-related information from the caudal brainstem. Recent data indicate the presence of glutamate-like immunoreactivity within this nucleus. The... more
The pontine parabrachial nucleus (PBN) is a major recipient of a diverse array of autonomic-related information from the caudal brainstem. Recent data indicate the presence of glutamate-like immunoreactivity within this nucleus. The effect of specific excitatory amino acid (EAA) receptor agonists and antagonists were studied in the lateral PBN (LPBN) by the use of whole-cell patch recordings in an in vitro brainstem slice preparation. Under current and voltage clamp conditions, independent bath applications of N-methyl-D-aspartate (NMDA; 10 microM), quisqualic acid (QUIS; 10 microM) and kainic acid (kainate; 10 microM) evoked membrane depolarization and an inward current in 28 of 31 LPBN neurons. In voltage clamp mode, the NMDA current (INMDA) was undetectable at potentials negative to -70 mV and a small inward current was observed at more depolarized potentials. However, in the absence of external Mg2+, the voltage dependence of INMDA was similar to that observed for QUIS and kainate. The allosteric modulation of the NMDA receptor by the strychnine-insensitive glycine binding site was examined by the application of the amino acid D-serine (0.5 mM). A marked and sustained potentiation of the steady-state INMDA (-60 mV holding potential) was observed. The selective NMDA-antagonist DL-2-amino-5-phosphonovaleric acid (APV; 10 microM) completely and reversibly blocked the NMDA-induced current, that was maximized in the absence of external Mg2+. Furthermore, this dose of APV was found to reversibly reduce the firing frequency of spontaneously active LPBN neurons.(ABSTRACT TRUNCATED AT 250 WORDS)