Nanomedicine is currently focused on the design and development of nanocarriers that enhance drug... more Nanomedicine is currently focused on the design and development of nanocarriers that enhance drug delivery to the brain to address unmet clinical needs for treating neuropsychiatric disorders and neurological diseases. Polymer and lipid-based drug carriers are advantageous for delivery to the central nervous system (CNS) due to their safety profiles, drug-loading capacity, and controlled-release properties. Polymer and lipid-based nanoparticles (NPs) are reported to penetrate the blood–brain barrier (BBB) and have been extensively assessed in in vitro and animal models of glioblastoma, epilepsy, and neurodegenerative disease. Since approval by the Food and Drug Administration (FDA) of intranasal esketamine for treatment of major depressive disorder, intranasal administration has emerged as an attractive route to bypass the BBB for drug delivery to the CNS. NPs can be specifically designed for intranasal administration by tailoring their size and coating with mucoadhesive agents or o...
Tryptophan and kynurenine pathway (KP) metabolites are implicated in the pathophysiology of depre... more Tryptophan and kynurenine pathway (KP) metabolites are implicated in the pathophysiology of depression. We aimed to investigate their plasma concentrations in medicated patients with depression (n = 94) compared to age- and sex-matched healthy controls (n = 57), and in patients with depression after electroconvulsive therapy (ECT) in a real-world clinical setting, taking account of co-variables including ECT modality and heterogenous psychopathology. Depression severity was assessed using the Hamilton Depression Rating Scale (HAM-D24). Tryptophan (TRP) and kynurenine (KYN) metabolite concentrations [anthranilic acid (AA), 3-hydroxyanthranilic acid (3HAA), picolinic acid (PA), kynurenic acid (KYNA), and xanthurenic acid (XA)] and KYNA/KYN and KYNA/quinolinic acid (QUIN) ratios were lower in patients compared to controls. For the total group there was no significant change in KP metabolites post-ECT or correlations with mood ratings. However, improvements in mood score were correlated with increased KYN, 3-hydroxykynurenine (3HK), 3HAA, QUIN, and KYN/TRP in a subgroup of unipolar depressed patients. Additionally, in remitters baseline KYN, 3HK, and QUIN were associated with baseline HAM-D24 scores, and changes in 3HK and 3HAA concentrations post-ECT correlated with improvement in mood. KYN, KYNA, AA, 3HK, XA, PA, and QUIN were increased in a smaller 3-month follow-up group (n=19) compared to pre-ECT concentrations. Overall, the results indicate that ECT mobilizes the KP, where a moderate association between selected metabolites and treatment response in unipolar depressed patients is evident.
OBJECTIVE Depression relapse after electroconvulsive therapy (ECT) is common (40% at 6 months). K... more OBJECTIVE Depression relapse after electroconvulsive therapy (ECT) is common (40% at 6 months). Ketamine has a robust antidepressant effect, but there are no reported studies of ketamine for depression relapse prevention. This pilot trial (NCT02414932) was designed to assess feasibility of the proposed trial protocol, including examining reasons for nonrecruitment, nonrandomization, and dropout. METHODS Patients with unipolar depression referred for ECT were monitored weekly for therapeutic response, using the 24-item Hamilton Rating Scale for Depression (monitoring phase). Those who met standard response criteria were invited to be randomized to a course of 4 once-weekly infusions of ketamine (0.5 mg/kg) or the active comparator, midazolam (0.045 mg/kg), over 40 minutes to examine trial processes (treatment phase). Participants were followed up for 6 months after ECT to assess for relapse. RESULTS One hundred seventy-five referrals were screened over 18 months, and 68% of eligible participants (n = 43) were recruited to the monitoring phase; 60.5% of participants met ECT response criteria (n = 26), but only 26% (6) of these consented to take part in the treatment phase. These were randomized (3 to ketamine and 3 to midazolam), and no participant completed the 4-week treatment protocol. Information was gathered on reasons for nonrecruitment, nonrandomization, and dropout, which included practical aspects of infusions and lack of interest in further treatment after response to ECT. CONCLUSIONS The proposed treatment protocol is not suitable for a definitive trial in our center. Information collected on reasons for dropout may inform future clinical trials of intravenous ketamine. TRIAL REGISTRATION www.clinicaltrials.gov NCT02414932.
Brain glia possess the rate limiting enzyme indoleamine 2, 3-dioxygenase (IDO) which catalyses th... more Brain glia possess the rate limiting enzyme indoleamine 2, 3-dioxygenase (IDO) which catalyses the conversion of tryptophan to kynurenine. Microglia also express kynurenine monooxygenase (KMO) and kynureninase (KYNU) which lead to the production of the free radical producing metabolites, 3-hydroxykynurenine and 3-hydroxyanthranillic acid respectively and subsequently production of the NMDA receptor agonist quinolinic acid. The aim of this study was to examine the effect of IFNγ-stimulated kynurenine pathway (KP) induction in microglia on neurite outgrowth and complexity, and to determine whether alterations could be abrogated using pharmacological inhibitors of the KP. BV-2 microglia were treated with IFNγ (5ng/ml) for 24h and conditioned media (CM) was placed on primary cortical neurons 3 days in vitro (DIV) for 48h. Neurons were fixed and neurite outgrowth and complexity was assessed using fluorescent immunocytochemistry followed by Sholl analysis. Results show increased mRNA expr...
The regional specific modulation of neuronal activation following drug administration is of inter... more The regional specific modulation of neuronal activation following drug administration is of interest to determine brain areas involved in the behavioural effects of experimental test compounds. In the current investigation the effects of the L-arginine related NOS inhibitor N(ω)-l-nitroarginine (L-NA) and the structurally unrelated selective neuronal NOS inhibitor 1-(2-Trifluoro-methyl-phenyl) imidazole (TRIM) were assessed in the rat for changes in regional c-FOS immunoreactivity, a marker of neuronal activation, upon exposure to the forced swimming test (FST). Behaviour and regional FOS and FosB/ΔFosB expression was assessed in naive animals and in animals exposed to stress with central serotonin-depletion which exhibit a stress related phenotype in the FST. Male Sprague-Dawley rats (n=5- 6 per group) were treated with the irreversible tryptophan hydroxylase inhibitor, DL-4-p-chlorophenylalanine (pCPA, 150mg/kg, i.p.), to achieve central serotonin-depletion followed by repeated exposures to restraint stress and were then subjected to the FST. 24, 5 and 1h prior to the test, animals were treated with either L-NA (10mg/kg, i.p.), TRIM (50mg/kg, i.p.) or saline vehicle (1mg/kg i.p). pCPA treatment coupled with restraint stress increased immobility in the FST compared to naïve controls. Both NOS inhibitors decreased immobility time in 5-HT depleted and stressed animals only in keeping with their antidepressant-like properties. Brain regions analyzed for c-FOS immunoreactivity included the pre-limbic cortex, lateral septum (LS), nucleus accumbens, paraventricular hypothalamic nucleus (PVN), central amygdala, hippocampus (dorsal dentate gyrus and ventral CA1), and the dorsal raphe nucleus (DRN). Exposure to the FST increased c-FOS immunoreactivity in the LS, PVN, dentate gyrus, vCA1 and the DRN when compared to non-FST exposed controls. FST-induced c-FOS immunoreactivity was further increased in the LS following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. By contrast, FST-induced c-FOS immunoreactivity was reduced in dorsal dentate gyrus, vCA1 and the DRN following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. There was no difference observed in FST-induced expression of c-FOS between naïve animals and animals exposed to pCPA and restraint stress. This combination however provoked an increase in FosB/ΔFosB immunoreactivity in the infra-limbic cortex and nucleus accumbens with a concomitant reduction in the lateral septum, suggesting alterations to long-term, adaptive neuronal activation. This study identified a pattern of enhanced and reduced FST-related c-FOS immunoreactivity indicative of a NO-regulated network where inhibition of NO leads to activation of the septum with concomitant inhibition of the hippocampus, and the DRN. No link between FST-induced regional expression of c-FOS and increased immobility in the FST was observed in animals exposed to pCPA and stress. However, the 5-HT depletion regime combined with restraint stress provoked regional changes in the expression of ΔFosB which may relate to increased immobility in the FST.
Abstract The N -methyl- d -aspartate receptor (NMDA-R) antagonist ketamine has repeatedly shown r... more Abstract The N -methyl- d -aspartate receptor (NMDA-R) antagonist ketamine has repeatedly shown rapid and sustained antidepressant effects following a single dose in a number of clinical studies. Since the adverse effects associated with ketamine limit its wider use in the clinic, investigations are instead aimed at developing “cleaner” ketamine compounds that could demonstrate a fast onset of action and sustained efficacy without incurring adverse effects. In this regard, targets located downstream of the NMDA-R, such as nitric oxide synthase (NOS), may represent novel avenues for treating neuropsychiatric disorders. Since nNOS couples to the NMDA-R via the postsynaptic protein PSD-95, strategies that target the PSD-95/nNOS interaction may also represent an interesting locus for the treatment of neuropsychiatric disorders. Here, we review the rationale for the development of glutamate and nitric oxide (NO)-modulating drugs for treating depression and highlight findings in the field, which provide a basis for ongoing drug development.
The international journal of neuropsychopharmacology / official scientific journal of the Collegium Internationale Neuropsychopharmacologicum (CINP), 2014
Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective trea... more Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective treatment available for severe depression. However, its use is associated with side-effects. The stimulus in ultrabrief pulse ECT (UBP ECT; pulse width 0.25-0.3 ms) is more physiological and has been reported to be associated with less cognitive side-effects, but its antidepressant effectiveness is not yet well established. Using electroconvulsive stimulation (ECS), the animal model of ECT, we previously reported UBP ECS to be significantly less effective than well-established BP ECS in eliciting behavioural, molecular and cellular antidepressant-related effects in naïve rats. We have now compared the effects of BP and UBP ECS in an animal model of depression related to exogenous supplementation with the stress-induced glucocorticoid hormone, corticosterone. Corticosterone administration resulted in an increase in immobility time in the forced swim test (FST) (p < 0.01) and decreases in t...
Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical test... more Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical tests and in the current investigation the brain penetrant NOS inhibitor N(ω)-nitro-L-arginine (l-NA) and the preferential inhibitor of neuronal NOS (nNOS) 1-(2-trifluoromethylphenyl) imidazole (TRIM) were assessed in the olfactory bulbectomised (OB) rat, a well-established animal model of depression. Magnetic resonance imaging (MRI) was employed to assess regional brain volumes, blood perfusion and T1 and T2 relaxometry times both with and without drug treatment. l-NA (10 mg/kg, once daily p.o. for 10 days) attenuated OB-related hyperactivity in the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;open field&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; test in a comparable fashion to the tricyclic antidepressant imipramine (20 mg/kg, once daily p.o. for 14 days) indicative of an antidepressant-like response in the model. Treatment with TRIM (50 mg/kg, once daily s.c.) attenuated OB-related hyperactivity following 7 days of treatment when compared to vehicle treated controls. OB is associated with enlarged ventricular volume, increased periventicular perfusion and a decrease in T2 relaxation times in cortical and hippocampal regions, with enhanced perfusion and reduced T2 times attenuated by L-NA treatment. L-NA treatment was also associated with an increase in T1 relaxation times in limbic and cortical regions and found to reduce resting state hippocampal blood perfusion in OB animals. Behavioural observations are consistent with an antidepressant action of NOS inhibitors where associated changes in perfusion and T2 relaxation times may be related to the antidepressant action of L-NA in the model.
Aryl hydrocarbon receptor (AhR) is a transcription factor that belongs to the basic helix-loop-he... more Aryl hydrocarbon receptor (AhR) is a transcription factor that belongs to the basic helix-loop-helix PAS (Per-Arnt-Sim homology domain) family known to mediate the toxic and carcinogenic effects of xenobiotics. Interestingly, AhR is widely expressed in the central nervous system, but its physiological and pathological roles are still unclear. To define the role of AhR in stroke, we used middle cerebral artery occlusion in mice and oxygen-glucose deprivation in rat cortical neurons. The results presented here show that the ischemic insult increases total and nuclear AhR levels and AhR transcriptional activity in neurons in vivo and in vitro. We also show that AhR has a causal role in acute ischemic damage because pharmacological or genetic loss-of-function approaches result in neuroprotection. Inhibition of cAMP response element-binding protein-dependent signaling may participate in the deleterious actions of AhR. Finally, we have also found that L-kynurenine, a tryptophan metabolite...
In this study we examined the impact of systemic treatment with the long-acting brain penetrant b... more In this study we examined the impact of systemic treatment with the long-acting brain penetrant b2adrenoceptor agonist clenbuterol on NFjB activity and IjB expression in rat brain. Clenbuterol decreased NFjB activity (p65 DNA binding) in nuclear extracts prepared from rat cortex and hippocampus for up to 8 h following a single treatment. This was accompanied by increased expression of IjBa mRNA and protein. The temporal increase in IjB protein expression paralleled the suppression of NFjB activity, suggesting that IjBa mediates the suppression NFjB activity observed. These actions of clenbuterol were prevented by pre-treatment with the non-selective b-adrenoceptor antagonist propranolol, the b2-adrenoceptor antagonist ICI-118,551, but not the b1-adrenoceptor antagonist metoprolol, suggesting that the effects of clenbuterol on IjBa expression and NFjB activity are mediated specifically by the b2-adrenoceptor. In addition, the actions of clenbuterol were mimicked by systemic administr...
Nanomedicine is currently focused on the design and development of nanocarriers that enhance drug... more Nanomedicine is currently focused on the design and development of nanocarriers that enhance drug delivery to the brain to address unmet clinical needs for treating neuropsychiatric disorders and neurological diseases. Polymer and lipid-based drug carriers are advantageous for delivery to the central nervous system (CNS) due to their safety profiles, drug-loading capacity, and controlled-release properties. Polymer and lipid-based nanoparticles (NPs) are reported to penetrate the blood–brain barrier (BBB) and have been extensively assessed in in vitro and animal models of glioblastoma, epilepsy, and neurodegenerative disease. Since approval by the Food and Drug Administration (FDA) of intranasal esketamine for treatment of major depressive disorder, intranasal administration has emerged as an attractive route to bypass the BBB for drug delivery to the CNS. NPs can be specifically designed for intranasal administration by tailoring their size and coating with mucoadhesive agents or o...
Tryptophan and kynurenine pathway (KP) metabolites are implicated in the pathophysiology of depre... more Tryptophan and kynurenine pathway (KP) metabolites are implicated in the pathophysiology of depression. We aimed to investigate their plasma concentrations in medicated patients with depression (n = 94) compared to age- and sex-matched healthy controls (n = 57), and in patients with depression after electroconvulsive therapy (ECT) in a real-world clinical setting, taking account of co-variables including ECT modality and heterogenous psychopathology. Depression severity was assessed using the Hamilton Depression Rating Scale (HAM-D24). Tryptophan (TRP) and kynurenine (KYN) metabolite concentrations [anthranilic acid (AA), 3-hydroxyanthranilic acid (3HAA), picolinic acid (PA), kynurenic acid (KYNA), and xanthurenic acid (XA)] and KYNA/KYN and KYNA/quinolinic acid (QUIN) ratios were lower in patients compared to controls. For the total group there was no significant change in KP metabolites post-ECT or correlations with mood ratings. However, improvements in mood score were correlated with increased KYN, 3-hydroxykynurenine (3HK), 3HAA, QUIN, and KYN/TRP in a subgroup of unipolar depressed patients. Additionally, in remitters baseline KYN, 3HK, and QUIN were associated with baseline HAM-D24 scores, and changes in 3HK and 3HAA concentrations post-ECT correlated with improvement in mood. KYN, KYNA, AA, 3HK, XA, PA, and QUIN were increased in a smaller 3-month follow-up group (n=19) compared to pre-ECT concentrations. Overall, the results indicate that ECT mobilizes the KP, where a moderate association between selected metabolites and treatment response in unipolar depressed patients is evident.
OBJECTIVE Depression relapse after electroconvulsive therapy (ECT) is common (40% at 6 months). K... more OBJECTIVE Depression relapse after electroconvulsive therapy (ECT) is common (40% at 6 months). Ketamine has a robust antidepressant effect, but there are no reported studies of ketamine for depression relapse prevention. This pilot trial (NCT02414932) was designed to assess feasibility of the proposed trial protocol, including examining reasons for nonrecruitment, nonrandomization, and dropout. METHODS Patients with unipolar depression referred for ECT were monitored weekly for therapeutic response, using the 24-item Hamilton Rating Scale for Depression (monitoring phase). Those who met standard response criteria were invited to be randomized to a course of 4 once-weekly infusions of ketamine (0.5 mg/kg) or the active comparator, midazolam (0.045 mg/kg), over 40 minutes to examine trial processes (treatment phase). Participants were followed up for 6 months after ECT to assess for relapse. RESULTS One hundred seventy-five referrals were screened over 18 months, and 68% of eligible participants (n = 43) were recruited to the monitoring phase; 60.5% of participants met ECT response criteria (n = 26), but only 26% (6) of these consented to take part in the treatment phase. These were randomized (3 to ketamine and 3 to midazolam), and no participant completed the 4-week treatment protocol. Information was gathered on reasons for nonrecruitment, nonrandomization, and dropout, which included practical aspects of infusions and lack of interest in further treatment after response to ECT. CONCLUSIONS The proposed treatment protocol is not suitable for a definitive trial in our center. Information collected on reasons for dropout may inform future clinical trials of intravenous ketamine. TRIAL REGISTRATION www.clinicaltrials.gov NCT02414932.
Brain glia possess the rate limiting enzyme indoleamine 2, 3-dioxygenase (IDO) which catalyses th... more Brain glia possess the rate limiting enzyme indoleamine 2, 3-dioxygenase (IDO) which catalyses the conversion of tryptophan to kynurenine. Microglia also express kynurenine monooxygenase (KMO) and kynureninase (KYNU) which lead to the production of the free radical producing metabolites, 3-hydroxykynurenine and 3-hydroxyanthranillic acid respectively and subsequently production of the NMDA receptor agonist quinolinic acid. The aim of this study was to examine the effect of IFNγ-stimulated kynurenine pathway (KP) induction in microglia on neurite outgrowth and complexity, and to determine whether alterations could be abrogated using pharmacological inhibitors of the KP. BV-2 microglia were treated with IFNγ (5ng/ml) for 24h and conditioned media (CM) was placed on primary cortical neurons 3 days in vitro (DIV) for 48h. Neurons were fixed and neurite outgrowth and complexity was assessed using fluorescent immunocytochemistry followed by Sholl analysis. Results show increased mRNA expr...
The regional specific modulation of neuronal activation following drug administration is of inter... more The regional specific modulation of neuronal activation following drug administration is of interest to determine brain areas involved in the behavioural effects of experimental test compounds. In the current investigation the effects of the L-arginine related NOS inhibitor N(ω)-l-nitroarginine (L-NA) and the structurally unrelated selective neuronal NOS inhibitor 1-(2-Trifluoro-methyl-phenyl) imidazole (TRIM) were assessed in the rat for changes in regional c-FOS immunoreactivity, a marker of neuronal activation, upon exposure to the forced swimming test (FST). Behaviour and regional FOS and FosB/ΔFosB expression was assessed in naive animals and in animals exposed to stress with central serotonin-depletion which exhibit a stress related phenotype in the FST. Male Sprague-Dawley rats (n=5- 6 per group) were treated with the irreversible tryptophan hydroxylase inhibitor, DL-4-p-chlorophenylalanine (pCPA, 150mg/kg, i.p.), to achieve central serotonin-depletion followed by repeated exposures to restraint stress and were then subjected to the FST. 24, 5 and 1h prior to the test, animals were treated with either L-NA (10mg/kg, i.p.), TRIM (50mg/kg, i.p.) or saline vehicle (1mg/kg i.p). pCPA treatment coupled with restraint stress increased immobility in the FST compared to naïve controls. Both NOS inhibitors decreased immobility time in 5-HT depleted and stressed animals only in keeping with their antidepressant-like properties. Brain regions analyzed for c-FOS immunoreactivity included the pre-limbic cortex, lateral septum (LS), nucleus accumbens, paraventricular hypothalamic nucleus (PVN), central amygdala, hippocampus (dorsal dentate gyrus and ventral CA1), and the dorsal raphe nucleus (DRN). Exposure to the FST increased c-FOS immunoreactivity in the LS, PVN, dentate gyrus, vCA1 and the DRN when compared to non-FST exposed controls. FST-induced c-FOS immunoreactivity was further increased in the LS following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. By contrast, FST-induced c-FOS immunoreactivity was reduced in dorsal dentate gyrus, vCA1 and the DRN following treatment with L-NA or TRIM when compared to vehicle-treated FST controls. There was no difference observed in FST-induced expression of c-FOS between naïve animals and animals exposed to pCPA and restraint stress. This combination however provoked an increase in FosB/ΔFosB immunoreactivity in the infra-limbic cortex and nucleus accumbens with a concomitant reduction in the lateral septum, suggesting alterations to long-term, adaptive neuronal activation. This study identified a pattern of enhanced and reduced FST-related c-FOS immunoreactivity indicative of a NO-regulated network where inhibition of NO leads to activation of the septum with concomitant inhibition of the hippocampus, and the DRN. No link between FST-induced regional expression of c-FOS and increased immobility in the FST was observed in animals exposed to pCPA and stress. However, the 5-HT depletion regime combined with restraint stress provoked regional changes in the expression of ΔFosB which may relate to increased immobility in the FST.
Abstract The N -methyl- d -aspartate receptor (NMDA-R) antagonist ketamine has repeatedly shown r... more Abstract The N -methyl- d -aspartate receptor (NMDA-R) antagonist ketamine has repeatedly shown rapid and sustained antidepressant effects following a single dose in a number of clinical studies. Since the adverse effects associated with ketamine limit its wider use in the clinic, investigations are instead aimed at developing “cleaner” ketamine compounds that could demonstrate a fast onset of action and sustained efficacy without incurring adverse effects. In this regard, targets located downstream of the NMDA-R, such as nitric oxide synthase (NOS), may represent novel avenues for treating neuropsychiatric disorders. Since nNOS couples to the NMDA-R via the postsynaptic protein PSD-95, strategies that target the PSD-95/nNOS interaction may also represent an interesting locus for the treatment of neuropsychiatric disorders. Here, we review the rationale for the development of glutamate and nitric oxide (NO)-modulating drugs for treating depression and highlight findings in the field, which provide a basis for ongoing drug development.
The international journal of neuropsychopharmacology / official scientific journal of the Collegium Internationale Neuropsychopharmacologicum (CINP), 2014
Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective trea... more Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective treatment available for severe depression. However, its use is associated with side-effects. The stimulus in ultrabrief pulse ECT (UBP ECT; pulse width 0.25-0.3 ms) is more physiological and has been reported to be associated with less cognitive side-effects, but its antidepressant effectiveness is not yet well established. Using electroconvulsive stimulation (ECS), the animal model of ECT, we previously reported UBP ECS to be significantly less effective than well-established BP ECS in eliciting behavioural, molecular and cellular antidepressant-related effects in naïve rats. We have now compared the effects of BP and UBP ECS in an animal model of depression related to exogenous supplementation with the stress-induced glucocorticoid hormone, corticosterone. Corticosterone administration resulted in an increase in immobility time in the forced swim test (FST) (p < 0.01) and decreases in t...
Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical test... more Nitric oxide synthase (NOS) inhibitors possess antidepressant-like properties in preclinical tests and in the current investigation the brain penetrant NOS inhibitor N(ω)-nitro-L-arginine (l-NA) and the preferential inhibitor of neuronal NOS (nNOS) 1-(2-trifluoromethylphenyl) imidazole (TRIM) were assessed in the olfactory bulbectomised (OB) rat, a well-established animal model of depression. Magnetic resonance imaging (MRI) was employed to assess regional brain volumes, blood perfusion and T1 and T2 relaxometry times both with and without drug treatment. l-NA (10 mg/kg, once daily p.o. for 10 days) attenuated OB-related hyperactivity in the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;open field&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; test in a comparable fashion to the tricyclic antidepressant imipramine (20 mg/kg, once daily p.o. for 14 days) indicative of an antidepressant-like response in the model. Treatment with TRIM (50 mg/kg, once daily s.c.) attenuated OB-related hyperactivity following 7 days of treatment when compared to vehicle treated controls. OB is associated with enlarged ventricular volume, increased periventicular perfusion and a decrease in T2 relaxation times in cortical and hippocampal regions, with enhanced perfusion and reduced T2 times attenuated by L-NA treatment. L-NA treatment was also associated with an increase in T1 relaxation times in limbic and cortical regions and found to reduce resting state hippocampal blood perfusion in OB animals. Behavioural observations are consistent with an antidepressant action of NOS inhibitors where associated changes in perfusion and T2 relaxation times may be related to the antidepressant action of L-NA in the model.
Aryl hydrocarbon receptor (AhR) is a transcription factor that belongs to the basic helix-loop-he... more Aryl hydrocarbon receptor (AhR) is a transcription factor that belongs to the basic helix-loop-helix PAS (Per-Arnt-Sim homology domain) family known to mediate the toxic and carcinogenic effects of xenobiotics. Interestingly, AhR is widely expressed in the central nervous system, but its physiological and pathological roles are still unclear. To define the role of AhR in stroke, we used middle cerebral artery occlusion in mice and oxygen-glucose deprivation in rat cortical neurons. The results presented here show that the ischemic insult increases total and nuclear AhR levels and AhR transcriptional activity in neurons in vivo and in vitro. We also show that AhR has a causal role in acute ischemic damage because pharmacological or genetic loss-of-function approaches result in neuroprotection. Inhibition of cAMP response element-binding protein-dependent signaling may participate in the deleterious actions of AhR. Finally, we have also found that L-kynurenine, a tryptophan metabolite...
In this study we examined the impact of systemic treatment with the long-acting brain penetrant b... more In this study we examined the impact of systemic treatment with the long-acting brain penetrant b2adrenoceptor agonist clenbuterol on NFjB activity and IjB expression in rat brain. Clenbuterol decreased NFjB activity (p65 DNA binding) in nuclear extracts prepared from rat cortex and hippocampus for up to 8 h following a single treatment. This was accompanied by increased expression of IjBa mRNA and protein. The temporal increase in IjB protein expression paralleled the suppression of NFjB activity, suggesting that IjBa mediates the suppression NFjB activity observed. These actions of clenbuterol were prevented by pre-treatment with the non-selective b-adrenoceptor antagonist propranolol, the b2-adrenoceptor antagonist ICI-118,551, but not the b1-adrenoceptor antagonist metoprolol, suggesting that the effects of clenbuterol on IjBa expression and NFjB activity are mediated specifically by the b2-adrenoceptor. In addition, the actions of clenbuterol were mimicked by systemic administr...
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