Noradrenaline modulates the spontaneous firing activities of Purkinje cells via α2-adrenergic receptor in mouse cerebellar cortex / 生理学报

Cerebellar Purkinje cells (PCs) exhibit two types of discharge activities: simple spike (SS) and complex spike (CS). Previous studies found that noradrenaline (NA) can inhibit CS and bidirectionally regulate SS, but the enhancement of NA on SS is overwhelmed by the strong inhibition of excitatory molecular layer interneurons. However, the mechanism underlying the effect of NA on SS discharge frequency is not clear. Therefore, in the present study, we examined the mechanism underlying the increasing effect of NA on SS firing of PC in mouse cerebellar cortex in vivo and in cerebellar slice by cell-attached and whole-cell recording technique and pharmacological methods. GABAA receptor was blocked by 100 µmol/L picrotoxin in the whole process. In vivo results showed that NA significantly reduced the number of spikelets of spontaneous CS and enhanced the discharge frequency of SS, but did not affect the discharge frequency of CS. In vitro experiments showed that NA reduced the number of CS spikelets and after hyperpolarization potential (AHP) induced by electrical stimulation, and increased the discharge frequency of SS. NA also reduced the amplitude of excitatory postsynaptic current (EPSC) of parallel fiber (PF)-PC and significantly increased the paired-pulse ratio (PPR). Application of yohimbine, an antagonist of α2-adrenergic receptor (AR), completely eliminated the enhancing effect of NA on SS. The α2-AR agonist, UK14304, also increased the frequency of SS. The β-AR blocker, propranolol, did not affect the effects of NA on PC. These results suggest that in the absence of GABAA receptors, NA could attenuate the synaptic transmission of climbing fiber (CF)-PC via activating α2-AR, inhibit CS activity and reduce AHP, thus enhancing the SS discharge frequency of PC. This result suggests that NA neurons of locus coeruleus can finely regulate PC signal output by regulating CF-PC synaptic transmission.

Phytohormone abscisic acid boosts pentobarbital-induced sleep through activation of GABA-A, PPARß and PPARγ receptor signaling / O fito-hormônio ácido abscísico estimula o sono induzido por fenobarbital por meio de ativação da sinalização de receptores GABA-A, PPARß e PPARγ

ABSTRACT Background: Sleep disorders induce anxiety and forgetfulness and change habits. The chemical hypnotic drugs currently used have serious side effects and, therefore, people are drawn towards using natural compounds such as plant-based healing agents. Abscisic acid (ABA) is produced in a variety of mammalian tissues and it is involved in many neurophysiological functions. Objective: To investigate the possible effect of ABA on pentobarbital-induced sleep and its possible signaling through GABA-A and PPAR (γ and β) receptors, in male Wistar rats. Methods: The possible effect of ABA (5 and 10 µg/rat, intracerebroventricularly) on sleep onset latency time and duration was evaluated in a V-maze model of sleep. Pentobarbital sodium (40 mg/kg, intraperitoneally) was injected to induce sleep 30 min after administration of ABA. PPARβ (GSK0660, 80 nM/rat), PPARγ (GW9662, 3 nM/rat) or GABA-A receptor (bicuculline, 6 µg/rat) antagonists were given 15 min before ABA injection. Diazepam (2 mg/kg, intraperitoneally) was used as a positive control group. Results: ABA at 5 µg significantly boosted the pentobarbital-induced subhypnotic effects and promoted induction of sleep onset in a manner comparable to diazepam treatment. Furthermore, pretreatment with bicuculline significantly abolished the ABA effects on sleep parameters, while the amplifying effects of ABA on the induction of sleep onset was not significantly affected by PPARβ or PPARγ antagonists. The sleep prolonging effect of ABA was significantly prevented by both PPAR antagonists. Conclusions: The data showed that ABA boosts pentobarbital-induced sleep and that GABA-A, PPARβ and PPARγ receptors are, at least in part, involved in ABA signaling.

RESUMO Introdução: Os distúrbios do sono induzem a ansiedade e esquecimento e mudam hábitos. Os medicamentos hipnóticos químicos utilizados atualmente têm efeitos colaterais graves e, portanto, as pessoas são atraídas para o uso de compostos naturais, como agentes de cura à base de plantas. O ácido abscísico (ABA) é produzido em uma variedade de tecidos de mamíferos e está envolvido em muitas funções neurofisiológicas. Objetivo: Investigar o possível efeito do ABA no sono induzido por pentobarbital e sua possível sinalização por meio dos receptores GABA-A e PPAR (γ e β), em ratos Wistar machos. Métodos: O possível efeito do ABA (5 e 10 µg/rato, intracerebroventricularmente) no tempo de latência e duração do início do sono foi avaliado em um modelo de labirinto em V de sono. Pentobarbital sódico (40 mg/kg, intraperitonealmente) foi injetado para induzir o sono 30 minutos após a administração de ABA. PPARβ (GSK0660, 80 nM/rato), PPARγ (GW9662, 3 nM/rato) ou antagonistas do receptor GABA-A (bicuculina, 6 µg/rato) foram administrados 15 minutos antes da injeção de ABA. Diazepam (2 mg/kg, intraperitonealmente) foi utilizado como grupo de controle positivo. Resultados: ABA a 5 µg aumentou significativamente os efeitos sub-hipnóticos induzidos por pentobarbital e promoveu a indução do início do sono de forma comparável ao tratamento com diazepam. Além disso, o pré-tratamento com bicuculina aboliu significativamente os efeitos do ABA nos parâmetros do sono, ao passo que os efeitos amplificadores do ABA na indução do início do sono não foram significativamente afetados pelos antagonistas do PPARβ ou PPARγ. O efeito de prolongamento do sono do ABA foi significativamente prevenido por ambos os antagonistas do PPAR. Conclusões: Os dados mostraram que o ABA estimula o sono induzido por pentobarbital e que os receptores GABA-A, PPARβ e PPARγ estão, pelo menos em parte, envolvidos na sinalização ABA.

Cancer Stem Cells are Depolarized Relative to Normal Stem Cells Derived from Human Livers

ABSTRACT Introduction and aim. The inability to distinguish cancer (CSCs) from normal stem cells (NSCs) has hindered attempts to identify safer, more effective therapies for hepatocellular carcinoma (HCC). The aim of this study was to document and compare cell membrane potential differences (PDs) of CSCs and NSCs derived from human HCC and healthy livers respectively and determine whether altered GABAergic innervation could explain the differences. Material and methods. Epithelial cell adhesion molecule (EpCAM) positive stem cells were isolated from human liver tissues by magnetic bead separations. Cellular PDs were recorded by microelectrode impalement of freshly isolated cells. GABAA receptor subunit expression was documented by reverse transcriptase polymerase chain reaction (RT-PCR) and immunofluorescence. Results. CSCs were significantly depolarized (-7.0 ± 1.3 mV) relative to NSCs (-23.0 ± 1.4 mV, p < 0.01). The depolarized state was associated with different GABAA receptor subunit expression profiles wherein phasic transmission, represented by GAGAA α3 subunit expression, was prevalent in CSCs while tonic transmission, represented by GABAA α6 subunit expression, prevailed in NSCs. In addition, GABAA subunits α3, β3, γ3 and δ were strongly expressed in CSCs while GABAA π expression was dominant in NSCs. CSCs and NSCs responded similarly to GABAA receptor agonists (ΔPD: 12.5 ± 1.2 mV and 11.0 ± 3.5 mV respectively). Conclusion. The results of this study indicate that CSCs are significantly depolarized relative to NSCs and these differences are associated with differences in GABAA receptor subunit expression. Together they provide new insights into the pathogenesis and possible treatment of human HCC.

Monoterpenoids (thymol, carvacrol and S-(+)-linalool) with anesthetic activity in silver catfish (Rhamdia quelen): evaluation of acetylcholinesterase and GABAergic activity

This study evaluated the anesthetic potential of thymol and carvacrol, and their influence on acetylcholinesterase (AChE) activity in the muscle and brain of silver catfish (Rhamdia quelen). The AChE activity of S-(+)-linalool was also evaluated. We subsequently assessed the effects of thymol and S-(+)-linalool on the GABAergic system. Fish were exposed to thymol and carvacrol (25, 50, 75, and 100 mg/L) to evaluate time for anesthesia and recovery. Both compounds induced sedation at 25 mg/L and anesthesia with 50-100 mg/L. However, fish exposed to carvacrol presented strong muscle contractions and mortality. AChE activity was increased in the brain of fish at 50 mg/L carvacrol and 100 mg/L thymol, and decreased in the muscle at 100 mg/L carvacrol. S-(+)-linalool did not alter AChE activity. Anesthesia with thymol was reversed by exposure to picrotoxin (GABAA antagonist), similar to the positive control propofol, but was not reversed by flumazenil (antagonist of benzodiazepine binding site), as observed for the positive control diazepam. Picrotoxin did not reverse the effect of S-(+)-linalool. Thymol exposure at 50 mg/L is more suitable than carvacrol for anesthesia in silver catfish, because this concentration did not cause any mortality or interference with AChE activity. Thymol interacted with GABAA receptors, but not with the GABAA/benzodiazepine site. In contrast, S-(+)-linalool did not act in GABAA receptors in silver catfish.

Estrous cycle and stress: influence of progesterone on the female brain

The female brain operates in a constantly changing chemical milieu caused by cyclical changes in gonadal hormones during the estrous cycle (menstrual cycle in women). Such hormones are highly lipophilic and pass readily from the plasma to the brain where they can influence neuronal function. It is becoming clear that the rapid reduction in peripheral circulating progesterone, which occurs during the late diestrous phase of the cycle, can trigger a withdrawal-like response, in which changes in GABA A receptor expression render hyper-responsive certain brain areas involved in processing responses to stressful stimuli. The periaqueductal gray matter (PAG) is recognised as an important region for integrating anxiety/defence responses. Withdrawal from progesterone, via actions of its neuroactive metabolite allopregnanolone, triggers up-regulation of extrasynaptic GABA A receptors on GABAergic neurons in the PAG. As a consequence, ongoing GABAergic tone on the output cells decreases, leading to an increase in functional excitability of the circuitry and enhanced responsiveness to stressful stimuli during the late diestrous phase. These changes during late diestrus could be prevented by short-term neurosteroid administration, timed to produce a more gradual fall in the peripheral concentration of allopregnanolone than the rapid decrease that occurs naturally, thus removing the trigger for the central withdrawal response.

The expression of GABA(A) receptor alpha1 and GABA(B) receptor 1 in medulla oblongata solitary nucleus and ambiguous nucleus in the cases of tramadol intoxication / 法医学杂志

OBJECTIVE@#To observe the expression of GABA(A) receptor alpha1 (GABA(A)alpha1) and GABA(B) receptor 1 (GABA(B)1) in human medulla oblongata solitary nucleus and ambiguous nucleus due to tramadol-induced death.@*METHODS@#GABA(A)alpha1 and GABA(B)1 were detected by immunohistochemical SP method in tramadol-induced death group and control group. All results were evaluated by images analysis system.@*RESULTS@#Low expression of GABA(A)alpha1 and GABA(B)1 were detected in solitary nucleus and ambiguous nucleus in the control brain tissue. In cases of tramadol-induced death, the expression of GABA(A)alpha1 and GABA(B)1 significantly increased.@*CONCLUSION@#The mechanism of tramadol intoxication death could be caused by respiratory depression induced by over-expression of GABA(A)alpha1 and GABA(B)1 in medulla oblongata solitary nucleus and ambiguous nucleus.

Expressions of GABA and GABA(A)R-alpha1 in the brain of rats poisoned by tetramine / 法医学杂志

Expressions of GABA and GABA(A)R-alpha1 in the brain of rats poisoned by Tetramine were analyzed to explore the intoxication mechanism. Methods Sixty rats were randomly divided into control, sham poisoned, high-dose poisoned (1.0 mg/kg tetramine) and low-dose poisoned (0.1 mg/kg) groups. The expressions of GABA and GABA(A)R-alpha1 in the brain of the poisoned rats were detected and analyzed by immunohistochemistry and imaging analyzer. Results The expressions of both GABA and GABA(A)R-alpha1 were diffusely seen in the brains of the control and shame poisoned rat groups with a moderate expression level, whereas the expressions of both GABA and GABA(A)R-alpha1 were decreased in the brains of the high-dose poisoned group. In the low-dose poisoned rat group, the expression of GABA initially decreased and reached its lowest level 6 hours after poisoning, and then started to show an increase and reached the level of control groups at day 3. The expressions level reached its peak at days 5-7 after poisoning and remained above the level of control groups till 10 days after poisoning. Similarly, the expression of GABA(A)R-alpha1 in the brains of the low-dose poisoned group initially decreased and reached its lowest level 6-12 hrs after poisoning, and then started to increase and reached the level of control groups at days 7-10 after poisoning, respectively. Conclusion The expression of both GABA and GABA(A)R-alpha1 decreased in the brains of the high-dose poisoned rat group and these changes of GABA and GABA(A)R-alpha1 expressions may be associated with underlying mechanism of tetramine poisoning.

Involvement of GABA-A receptor chloride channel complex in isolation stress-induced free choice ethanol consumption in rats.

The present study revealed the effect of diazepam, a benzodiazepine, and progesterone, a pregnane precursor of neurosteroids, which act via modulating GABA-A chloride channel complex on the isolation stress-induced free choice ethanol consumption in adult rats. Isolation stress for 24 hr over a period of 6 days produced a significant increase in ethanol consumption, which persisted during the 6-day recovery period. Pretreating the animals with diazepam (5 mg/kg, i.p.), or progesterone (5 mg/kg, i.p.), blocked the isolation stress-induced increase in ethanol consumption. Bicuculline (2 mg/kg, i.p.), a GABA-A receptor antagonist significantly attenuated the effect of both diazepam and progesterone on stress-induced modulation of ethanol consumption. Isolation stress also caused an increase in total fluid consumption, which was antagonised by both diazepam and progesterone. Like ethanol consumption, this effect of diazepam and progesterone on isolation stress-induced increase in total fluid consumption was attenuated by bicuculline. Neither diazepam nor progesterone produced an increase in ethanol consumption in non-stressed rats. However, unlike diazepam, progesterone administration to non-stressed rats caused a significant increase in total fluid consumption. Results of the present study thus show that GABAergic mechanisms may be playing an important role in isolation stress-induced increase in ethanol consumption.

Evidence for presence of GABA-ergic receptor mediated dispersion in isolated scale melanophores of a carp, Cirrhinus mrigala Ham.

Effects of GABA-ergic agonists and antagonists were examined on the melanophores of a carp C. mrigala in vitro. GABA and baclofen both induced concentration - related dispersion in fish melanophores. Denervation of the melanophores by reserpine treatment potentiated the sensitivity of the melanophores to GABA. While denervation by cooling treatment inhibited the sensitivity of the melanophores to GABA, atropine, bicuculline and pentylenetetrazole all inhibited the dispersal responses of the melanophores induced by higher concentrations of GABA. 5-aminovaleric acid also significantly inhibited the dispersion of the melanophores induced either by GABA or baclofen. It is concluded that GABA-ergic agonist induced dispersal responses in C mrigala melanophores are mediated through specific GABA receptors. The presence of both GABAA and GABAB receptors in this fish melanophores has been indicated.

Effects of GABA on pancreatic exocrine secretion of rats

Since GABA and its related enzymes had been determined in beta-cells of pancreas islets, effects of GABA on pancreatic exocrine secretion were investigated in the isolated perfused rat pancreas. GABA, given intra-arterially at concentrations of 3, 10, 30 and 100 microM, did not exert any influence on spontaneous or secretin (12 pM)-induced pancreatic exocrine secretion. However, GABA further elevated cholecystokinin (10 pM)-, gastrin-releasing peptide (100 pM)- or electrical field stimulation-induced pancreatic secretions of fluid and amylase, dose-dependently. The GABA-enhanced CCK-induced pancreatic secretions were completely blocked by bicuculline (10 microM), a GABAA receptor antagonist but not affected by saclofen (10 microM), a GABA(B) receptor antagonist. The enhancing effects of GABA (30 microM) on CCK-induced pancreatic secretions were not changed by tetrodotoxin (1 microM) but partially reduced by cyclo-(7-aminoheptanonyl-Phe-D-Trp-Lys-Thr[BZL]) (10 microM), a somatostatin antagonist. In conclusion, GABA enhances pancreatic exocrine secretion induced by secretagogues, which stimulate enzyme secretion predominantly, via GABA(A) receptors in the rat pancreas. The enhancing effect of GABA is partially mediated by inhibition of islet somatostatin release. GABA does not modify the activity of intrapancreatic neurons.