Exploring the transition from inter-ictal to ictal epileptiform discharges(IDs) and how GABAAreceptormediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment.We ...Exploring the transition from inter-ictal to ictal epileptiform discharges(IDs) and how GABAAreceptormediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment.We used Mg2+-free artificial cerebrospinal fluid(ACSF) to induce epileptiform discharges in juvenile mouse hippocampal slices and used a micro-electrode array to record the discharges. After the slices were exposed to Mg2+-free ACSF for 10 min–20 min, synchronous recurrent seizurelike events were recorded across the slices, and each event evolved from inter-ictal epileptiform discharges(IIDs) to pre-ictal epileptiform discharges(PIDs), and then to IDs.During the transition from IIDs to PIDs, the duration of discharges increased and the inter-discharge interval decreased. After adding 3 lmol/L of the GABAAreceptor agonist muscimol, PIDs and IDs disappeared, and IIDs remained. Further, the application of 10 lmol/L muscimol abolished all the epileptiform discharges. When the GABAAreceptor antagonist bicuculline was applied at 10 lmol/L, IIDs and PIDs disappeared, and IDs remained at decreased intervals. These results indicated that there are dynamic changes in the hippocampal network preceding the onset of IDs, and GABAAreceptor activity suppresses the transition from IIDs to IDs in juvenile mouse hippocampus.展开更多
The γ-aminobutyric acid neurotransmitter in the spinal cord dorsal horn plays an important role in pain modulation through primary afferent-mediated presynaptic inhibition. The weakening of γ-aminobutyric acid-media...The γ-aminobutyric acid neurotransmitter in the spinal cord dorsal horn plays an important role in pain modulation through primary afferent-mediated presynaptic inhibition. The weakening of γ-aminobutyric acid-mediated presynaptic inhibition may be an important cause of neuropathic pain. γ-aminobutyric acid-mediated presynaptic inhibition is related to the current strength of γ-aminobutyric acid A receptor activation. In view of this, the whole-cell patch-clamp technique was used here to record the change in muscimol activated current of dorsal root ganglion neurons in a chronic constriction injury model. Results found that damage in rat dorsal root ganglion neurons following application of muscimol caused concentration-dependent activation of current, and compared with the sham group, its current strength and γ-aminobutyric acid A receptor protein expression decreased. Immunofluorescence revealed that γ-aminobutyric acid type A receptor α2 subunit protein expression decreased and was most obvious at 12 and 15 days after modeling. Our experimental findings confirmed that the y-aminobutyric acid type A receptor α2 subunit in the chronic constriction injury model rat dorsal root ganglion was downregulated, which may be one of the reasons for the reduction of injury in dorsal root ganglion neurons following muscimol-activated currents.展开更多
The influence of γ-aminobutyric type-A (GABA<sub>A</sub>) receptors agonist (muscimol hydrobromide, 0.1 μg/0.5 μl) injections into the right or left basolateral amygdala (BLA) on the behavior of high-an...The influence of γ-aminobutyric type-A (GABA<sub>A</sub>) receptors agonist (muscimol hydrobromide, 0.1 μg/0.5 μl) injections into the right or left basolateral amygdala (BLA) on the behavior of high-anxiety (HA) and low-anxiety (LA) rats subjected to the elevated plus-maze (EPM) test was investigated. Anxiolytic-like effects (increase of open-arm entries and open-arm time) was revealed only after administration of muscimol into the left (but not right) amygdala of HA animals. No effect was observed upon administration of muscimol to LA rats. These findings suggest an important role in anxiety regulation of the amygdalar GABA levels, and the assumed GABA hemispheric lateralization.展开更多
Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA e...Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA evoked evoked by high potassium stimulation in a dose dependent manner, whereas beclofen, a GABAB receptor agonist, had no significant effect on the release. Furthermore, it was found that the suppressive effect of muscimol could be antagonized invariably by bicuculline, a GABAA receptor antagonist. These results suggest that the release of [3H] GABA from rat cerebral conical GABA neurous may be modulated by presynaptic GABAA autoreceptor.展开更多
In this study we investigated whether GABAA receptors of the basolateral amygdala(BLA) interact with the effect of dexamethasone on the retrieval stage of memory.Adult male Wistar rats were bilaterally cannulated in t...In this study we investigated whether GABAA receptors of the basolateral amygdala(BLA) interact with the effect of dexamethasone on the retrieval stage of memory.Adult male Wistar rats were bilaterally cannulated in the BLA by stereotaxic surgery.The animals were trained in step-through apparatus by induction of electric shock(1.5 mA,3 s) and were tested for memory retrieval after 1 d.The time of latency for entering the dark compartment of the instrument and the time spent by rats in this chamber were recorded for evaluation of the animals' retrieval in passive avoidance memory.Administration of dexamethasone(0.3 and 0.9 mg/kg,subcutaneously(s.c.)),immediately after training,enhanced memory retrieval.This effect was reduced by intra-BLA microinjection of muscimol(0.125,0.250 and 0.500 μg/rat),when administered before 0.9 mg/kg of dexamethasone.Microinjection of bicuculline(0.75 μg/rat,intra-BLA) with an ineffective dose of dexamethasone(0.1 mg/kg,s.c.) increased memory retrieval.However,the same doses of muscimol and bicuculline without dexamethasone did not affect memory processes.Our data support reports that dexamethasone enhances memory retrieval.It seems that GABAA receptors of the BLA mediate the effect of dexamethasone on memory retrieval in rats.展开更多
Parkinson’s disease (PD) is characterized by degeneration of nigrostriatal dopamine (DA) neurons. The primary drug used to treat PD symptoms is L-DOPA, but side effects such as dyskinesias limit its use. Previous fin...Parkinson’s disease (PD) is characterized by degeneration of nigrostriatal dopamine (DA) neurons. The primary drug used to treat PD symptoms is L-DOPA, but side effects such as dyskinesias limit its use. Previous findings show that L-DOPA treatment induces extracellular signal-regulated kinase (ERK1/2), a MAP-kinase protein. γ-aminobutyric acid (GABA) is intimately involved in basal ganglia function. Our previous study using a unilaterally lesioned rat model of PD indicated that elevating GABA levels by GABA transaminase inhibitor, aminooxyacetic acid significantly attenuated L-DOPA-induced ERK phosphorylation in the striatum and substantia nigra (SN). The aim of the present study was to assess the role of GABA-A and GABA-B receptor by using a selective agonists, muscimol and baclofen respectively, on L-DOPA-induced ERK phosphorylation in the striatum and SN. Unilaterally 6-OHDA-lesioned rats were prescreened by apomorphine induced rotation test for the extent of DA loss. Lesioned rats were treated with L-DOPA alone or after muscimol or baclofen pretreatment. Appropriate control groups were used. Phospho-ERK levels, tyrosine hydroxylase (to ascertain DA loss) and substance P (an indirect marker for DA loss) levels were assessed by immunohistochemistry using coronal slices at the level of striatum and SN. L-DOPA administration induced a robust increase (>300%) in phospho-ERK1/2 levels in the striatum and SN. Muscimol as well as baclofen pretreatment attenuated the L-DOPA-induced increase in phospho-ERK1/2 levels by >60% in the striatum and SN. Muscimol and baclofen pretreatment also greatly reduced the number of L-DOPA induced phospho-ERK1/2 stained cells in the striatum as well as the contralateral rotational behavior. The present data taken together with our previous study indicate that the L-DOPA induced increase in ERK1/2 is attenuated by GABA via a GABA-A and GABA-B receptor linked mechanism. The study provides further insight into a dopamine-GABA-ERK interaction in the therapeutic and/or side effects of L展开更多
Previous studies have shown that CCK-8 has distinct antiopioid effect in the central sites related with pain control and blood pressure control. The aim of this study was to explore the receptor mechanism by which CCK...Previous studies have shown that CCK-8 has distinct antiopioid effect in the central sites related with pain control and blood pressure control. The aim of this study was to explore the receptor mechanism by which CCK-8 antagonized the depressor effect of u-and k-opioid agonists, and to observe whether CCK-8 could antagonize the depressor effect induced by muscimol, a nonopioid substance. The results showed that (ⅰ) The antagonistic effect of CCK-8 on opioid-induced hypotension could be blocked by intrathecal (i.t.) administration of CCK-B antagonist L-365, 260 at nanogram doses, or by CCK-A antagonist devazepide at doses 20—40 times higher than L-365, 260, indicating that it was the CCK-B receptor which mediates the antiopioid effect. (ⅱ) The depressor effect induced by intrathecal muscimol, a GABA agonist, was blocked neither by naloxone nor by CCK-8, supporting the notion that CCK-8 is an endogenous opioid antagonist rather thana universal anti-hypotension agent.展开更多
基金supported by the Key Basic Research Project of Science and Technology Commission of Shanghai (13DJ1400303)the Shanghai Jiao Tong University Fund for Interdisciplinary Research for Medical Applications (YG2012ZD08)the Seed Fund of Ren Ji Hospital (RJ ZZ13-005)
文摘Exploring the transition from inter-ictal to ictal epileptiform discharges(IDs) and how GABAAreceptormediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment.We used Mg2+-free artificial cerebrospinal fluid(ACSF) to induce epileptiform discharges in juvenile mouse hippocampal slices and used a micro-electrode array to record the discharges. After the slices were exposed to Mg2+-free ACSF for 10 min–20 min, synchronous recurrent seizurelike events were recorded across the slices, and each event evolved from inter-ictal epileptiform discharges(IIDs) to pre-ictal epileptiform discharges(PIDs), and then to IDs.During the transition from IIDs to PIDs, the duration of discharges increased and the inter-discharge interval decreased. After adding 3 lmol/L of the GABAAreceptor agonist muscimol, PIDs and IDs disappeared, and IIDs remained. Further, the application of 10 lmol/L muscimol abolished all the epileptiform discharges. When the GABAAreceptor antagonist bicuculline was applied at 10 lmol/L, IIDs and PIDs disappeared, and IDs remained at decreased intervals. These results indicated that there are dynamic changes in the hippocampal network preceding the onset of IDs, and GABAAreceptor activity suppresses the transition from IIDs to IDs in juvenile mouse hippocampus.
基金supported by the Youth Science and Technology Innovation Special Foundation of Xinjiang Production and Construction Corps, China, No. 2010JC33
文摘The γ-aminobutyric acid neurotransmitter in the spinal cord dorsal horn plays an important role in pain modulation through primary afferent-mediated presynaptic inhibition. The weakening of γ-aminobutyric acid-mediated presynaptic inhibition may be an important cause of neuropathic pain. γ-aminobutyric acid-mediated presynaptic inhibition is related to the current strength of γ-aminobutyric acid A receptor activation. In view of this, the whole-cell patch-clamp technique was used here to record the change in muscimol activated current of dorsal root ganglion neurons in a chronic constriction injury model. Results found that damage in rat dorsal root ganglion neurons following application of muscimol caused concentration-dependent activation of current, and compared with the sham group, its current strength and γ-aminobutyric acid A receptor protein expression decreased. Immunofluorescence revealed that γ-aminobutyric acid type A receptor α2 subunit protein expression decreased and was most obvious at 12 and 15 days after modeling. Our experimental findings confirmed that the y-aminobutyric acid type A receptor α2 subunit in the chronic constriction injury model rat dorsal root ganglion was downregulated, which may be one of the reasons for the reduction of injury in dorsal root ganglion neurons following muscimol-activated currents.
文摘The influence of γ-aminobutyric type-A (GABA<sub>A</sub>) receptors agonist (muscimol hydrobromide, 0.1 μg/0.5 μl) injections into the right or left basolateral amygdala (BLA) on the behavior of high-anxiety (HA) and low-anxiety (LA) rats subjected to the elevated plus-maze (EPM) test was investigated. Anxiolytic-like effects (increase of open-arm entries and open-arm time) was revealed only after administration of muscimol into the left (but not right) amygdala of HA animals. No effect was observed upon administration of muscimol to LA rats. These findings suggest an important role in anxiety regulation of the amygdalar GABA levels, and the assumed GABA hemispheric lateralization.
文摘Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA evoked evoked by high potassium stimulation in a dose dependent manner, whereas beclofen, a GABAB receptor agonist, had no significant effect on the release. Furthermore, it was found that the suppressive effect of muscimol could be antagonized invariably by bicuculline, a GABAA receptor antagonist. These results suggest that the release of [3H] GABA from rat cerebral conical GABA neurous may be modulated by presynaptic GABAA autoreceptor.
基金supported by the Shahid Chamran University of Ahvaz,Iran
文摘In this study we investigated whether GABAA receptors of the basolateral amygdala(BLA) interact with the effect of dexamethasone on the retrieval stage of memory.Adult male Wistar rats were bilaterally cannulated in the BLA by stereotaxic surgery.The animals were trained in step-through apparatus by induction of electric shock(1.5 mA,3 s) and were tested for memory retrieval after 1 d.The time of latency for entering the dark compartment of the instrument and the time spent by rats in this chamber were recorded for evaluation of the animals' retrieval in passive avoidance memory.Administration of dexamethasone(0.3 and 0.9 mg/kg,subcutaneously(s.c.)),immediately after training,enhanced memory retrieval.This effect was reduced by intra-BLA microinjection of muscimol(0.125,0.250 and 0.500 μg/rat),when administered before 0.9 mg/kg of dexamethasone.Microinjection of bicuculline(0.75 μg/rat,intra-BLA) with an ineffective dose of dexamethasone(0.1 mg/kg,s.c.) increased memory retrieval.However,the same doses of muscimol and bicuculline without dexamethasone did not affect memory processes.Our data support reports that dexamethasone enhances memory retrieval.It seems that GABAA receptors of the BLA mediate the effect of dexamethasone on memory retrieval in rats.
文摘Parkinson’s disease (PD) is characterized by degeneration of nigrostriatal dopamine (DA) neurons. The primary drug used to treat PD symptoms is L-DOPA, but side effects such as dyskinesias limit its use. Previous findings show that L-DOPA treatment induces extracellular signal-regulated kinase (ERK1/2), a MAP-kinase protein. γ-aminobutyric acid (GABA) is intimately involved in basal ganglia function. Our previous study using a unilaterally lesioned rat model of PD indicated that elevating GABA levels by GABA transaminase inhibitor, aminooxyacetic acid significantly attenuated L-DOPA-induced ERK phosphorylation in the striatum and substantia nigra (SN). The aim of the present study was to assess the role of GABA-A and GABA-B receptor by using a selective agonists, muscimol and baclofen respectively, on L-DOPA-induced ERK phosphorylation in the striatum and SN. Unilaterally 6-OHDA-lesioned rats were prescreened by apomorphine induced rotation test for the extent of DA loss. Lesioned rats were treated with L-DOPA alone or after muscimol or baclofen pretreatment. Appropriate control groups were used. Phospho-ERK levels, tyrosine hydroxylase (to ascertain DA loss) and substance P (an indirect marker for DA loss) levels were assessed by immunohistochemistry using coronal slices at the level of striatum and SN. L-DOPA administration induced a robust increase (>300%) in phospho-ERK1/2 levels in the striatum and SN. Muscimol as well as baclofen pretreatment attenuated the L-DOPA-induced increase in phospho-ERK1/2 levels by >60% in the striatum and SN. Muscimol and baclofen pretreatment also greatly reduced the number of L-DOPA induced phospho-ERK1/2 stained cells in the striatum as well as the contralateral rotational behavior. The present data taken together with our previous study indicate that the L-DOPA induced increase in ERK1/2 is attenuated by GABA via a GABA-A and GABA-B receptor linked mechanism. The study provides further insight into a dopamine-GABA-ERK interaction in the therapeutic and/or side effects of L
基金Project supported by the National Natural Science Foundation of China
文摘Previous studies have shown that CCK-8 has distinct antiopioid effect in the central sites related with pain control and blood pressure control. The aim of this study was to explore the receptor mechanism by which CCK-8 antagonized the depressor effect of u-and k-opioid agonists, and to observe whether CCK-8 could antagonize the depressor effect induced by muscimol, a nonopioid substance. The results showed that (ⅰ) The antagonistic effect of CCK-8 on opioid-induced hypotension could be blocked by intrathecal (i.t.) administration of CCK-B antagonist L-365, 260 at nanogram doses, or by CCK-A antagonist devazepide at doses 20—40 times higher than L-365, 260, indicating that it was the CCK-B receptor which mediates the antiopioid effect. (ⅱ) The depressor effect induced by intrathecal muscimol, a GABA agonist, was blocked neither by naloxone nor by CCK-8, supporting the notion that CCK-8 is an endogenous opioid antagonist rather thana universal anti-hypotension agent.
