CCL28 in the mouse hippocampal CA1 area and the dentate gyrus during and after pilocarpine-induced status epilepticus

The present study showed a wide presence of CCL28 in mouse CNS, including cerebral, cerebellum, brain stem and spinal cord. In hippocampus, the expression of CCL28 at both mRNA and protein level was clarified. The CCL28 expression was mainly localized in pyramidal cells of CA area, granular cells of dentate gyrus and some interneurons in CA area and hilus. Double-labelling immunocytochemistry revealed that most of calbindin, calretinin and parvalbumin immunopositive neurons expressed CCL28. During and after pilocarpine induced status epilepticus (SE), a down-regulated expression of CCL28 in hippocampal interneurons in the CA1 area and in the hilus of the dentate gyrus was demonstrated. The present study may, therefore provide evidence that CCL28 may have a novel role in CNS and may be involved in the loss of hippocampal interneurons, and subsequent disinhibition of pyramidal neurons.     

Extracellular matrix protein SC1/hevin in the hippocampus following pilocarpine-induced status epilepticus

Pilocarpine-induced status epilepticus (SE) mimics many features of temporal lobe epilepsy and is a useful model to study neural changes that result from prolonged seizure activity. In this study, distribution of the anti-adhesive extracellular matrix protein SC1 was examined in the rat hippocampus following SE. Western blotting showed decreased levels of SC1 protein in the week following SE. Immunohistochemistry demonstrated that the decrease in overall SC1 protein levels was reflected by a reduction of SC1 signal in granule cells of the dentate gyrus. Interestingly, levels of SC1 protein in neurons of the seizure-resistant CA2 sector of the hippocampus did not change throughout the seizure time course. However, at 1 day post-SE, a subset of neurons of the hippocampal CA1, CA3, and hilar regions, which are noted for extensive neuronal degeneration after SE, exhibited a transient increase in SC1 signal. Neurons exhibiting enhanced SC1 signal were not detected at 7 days post-SE. The cellular stress response was also examined. A prominent induction of heat-shock protein (Hsp70) and Hsp27 was detected following SE, while levels of constitutively expressed Hsp40, Hsp90, Hsp110, and Hsc70 showed little change at the time points examined. The subset of neurons that demonstrated a transient increase in SC1 colocalized with the cellular stress marker Hsp70, the degeneration marker Fluoro-Jade B, and the neuron activity marker activity-regulated cytoskeleton-associated protein (Arc). Taken together, these findings suggest that SC1 may be a component of the 'matrix response' involved in remodeling events associated with neuronal degeneration following neural injury.     

GABA metabolism in the substantia nigra,cortex, and hippocampus during status epilepticus

The metabolism of GABA and other amino acids was studied in the substantia nigra, the hippocampus and the parietal cortex of rats following microinjections of GAMMA-vinyl-GABA during status epilepticus induced by lithium and pilocarpine. GABA metabolism showed striking regional variations. In controls, both GABA concentration and rate of GABA synthesis were highest in the substantia nigra and lowest in cortex, as expected. In substantia nigra, status epilepticus resulted in a 2 1/2 fold decline in the rate of GABA synthesis and in a 307% increase in the turnover time of the GABA pool. In hippocampus, the rate of GABA synthesis was not altered significantly, but the turnover time of the GABA pool was 284% of controls, and the size of that pool increased to 208% of controls. By contrast, in cortex, where seizure activity is limited in this model, the rate of GABA synthesis increased to 230% of controls while pool size and turnover time did not change. Aspartate concentration decreased in all three brain regions. These data suggest that the observed reduction of the rate of GABA synthesis in substantia nigra could play a key role in seizure spread in this model of status epilepticus.Special Issue dedicated to Claude Baxter.     

Activity-dependent changes of the hippocampal CA3–CA1 synapse during the acquisition of associative learning in conscious mice

Contemporary neuroscientists are paying increasing attention to subcellular, molecular and electrophysiological mechanisms underlying learning and memory processes. Recent efforts have addressed the development of transgenic mice affected at different stages of the learning process, or emulating pathological conditions involving cognition and motor-learning capabilities. However, a parallel effort is needed to develop stimulating and recording techniques suitable for use in behaving mice, in order to grasp activity-dependent neural changes taking place during the very moment of the process. These in vivo models should integrate the fragmentary information collected by different molecular and in vitro approaches. In this regard, long-term potentiation (LTP) has been proposed as the neural mechanism underlying synaptic plasticity. Moreover, N -methyl- d -aspartate (NMDA) receptors are accepted as the molecular substrate of LTP. It now seems necessary to study the relationship of both LTP and NMDA receptors with the plastic changes taking place, in selected neural structures, during actual learning. Here, we review data on the involvement of the hippocampal CA3–CA1 synapse in the acquisition of classically conditioned eyelid conditioned responses (CRs) in behaving mice. Available data show that LTP, evoked by high-frequency stimulation of Schaffer collaterals, disturbs both the acquisition of CRs and the physiological changes that occur at the CA3–CA1 synapse during learning. Moreover, the administration of NMDA-receptor antagonists is able not only to prevent LTP induction in vivo , but also to hinder the formation of both CRs and functional changes in strength of the CA3–CA1 synapse. Thus, there is experimental evidence relating activity-dependent synaptic changes taking place during actual learning with LTP mechanisms and with the role of NMDA receptors in both processes.     

Modulation of intracellular calcium changes and glutamate release by neuropeptide Y1 and Y2 receptors in the rat hippocampus: differential effects in CA1, CA3 and dentate gyrus

In the present work, we investigated the role of pre- and post-synaptic neuropeptide Y1 (NPY1) and Y2 receptors on the calcium responses and on glutamate release in the rat hippocampus. In cultured hippocampal neurones, we observed that only NPY1 receptors are involved in the modulation of intracellular free calcium concentration ([Ca(2+)](i)). In 88% of the neurones analysed, the increase in the [Ca(2+)](i), in response to depolarization with 50 mM KCl, was inhibited by 1 microM [Leu31,Pro34]NPY, whereas 300 nM NPY13-36 was without effect. However, studies with hippocampal synaptosomes showed that both NPY1 and Y2 receptors can modulate the [Ca(2+)](i) and glutamate release. The pharmacological characterization of the NPY-induced inhibition of glutamate release indicated that Y2 receptors play a predominant role, both in the modulation of Ca(2+)-dependent and -independent glutamate release. However, we could distinguish between Y1 and Y2 receptors by using [Leu31,Pro34]NPY and NPY13-36. Active pre-synaptic Y1 receptors are present in the dentate gyrus (DG) as well as in the CA3 subregion, but its activity was not revealed by using the endogenous agonist, NPY. Concerning the Y2 receptors, they are present in the three subregions (CA1, CA3 and DG) and were activated by either NPY13-36 or NPY. The present data support a predominant role for NPY2 receptors in mediating NPY-induced inhibition of glutamate release in the hippocampus, but the physiological relevance of the presently described DG and CA3 pre-synaptic NPY1 receptors remains to be clarified.     

Genetic deletion of the neuronal glutamate transporter,EAAC1, results in decreased neuronal death after pilocarpine-induced status epilepticus

Excitatory amino acid carrier 1 (EAAC1 also called EAAT3) is a Na⁺-dependent glutamate transporter expressed by both glutamatergic and GABAergic neurons. It provides precursors for the syntheses of glutathione and GABA and contributes to the clearance of synaptically released glutamate. Mice deleted of EAAC1 are more susceptible to neurodegeneration in models of ischemia, Parkinson’s disease, and aging. Antisense knock-down of EAAC1 causes an absence seizure-like phenotype. Additionally, EAAC1 expression increases after chemonvulsant-induced seizures in rodent models and in tissue specimens from patients with refractory epilepsy. The goal of the present study was to determine if the absence of EAAC1 affects the sensitivity of mice to seizure-induced cell death. A chemoconvulsant dose of pilocarpine was administered to EAAC1^−/− mice and to wild-type controls. Although EAAC1^−/− mice experienced increased latency to seizure onset, no significant differences in behavioral seizure severity or mortality were observed. We examined EAAC1 immunofluorescence 24 h after pilocarpine administration and confirmed that pilocarpine causes an increase in EAAC1 protein. Forty-eight hours after induction of seizures, cell death was measured in hippocampus and in cortex using Fluoro-Jade C. Surprisingly, there was ∼2-fold more cell death in area CA1 of wild-type mice than in the corresponding regions of the EAAC1^−/− mice. Together, these studies indicate that absence of EAAC1 results in either a decrease in pilocarpine-induced seizures that is not detectable by behavioral criteria (surprising, since EAAC1 provides glutamate for GABA synthesis), or that the absence of EAAC1 results in less pilocarpine/seizure-induced cell death, possible explanations as discussed.     

晚时相长时程增强翻转前后大鼠海马CA1区AMPAR/GluR2的表达

晚时相长时程增强(late-phase long-term potentiation,L-LTP)对于海马长期记忆的维持具有非常重要的作用,然而L-LTP可被诱导之后的神经元活动所翻转。本实验旨在研究海马CA1区L-LTP的翻转是否有突触前机制的参与以及L-LTP翻转前后AMPARs的表达有无变化。实验采用海马脑薄片细胞外场电位记录技术,使用强直刺激(high-frequency stimulation,HFS)诱导出CA1区L-LTP,2h后用两组间隔10min的高强度的双脉冲低频刺激(high-intensity paired-pulse low frequency stimulation,HI-PP-LFS)诱导L-LTP翻转。在LTP诱导前、诱导2h后、翻转后均给予一个双脉冲刺激,观察双脉冲比值(paired-pulse ratio,PPR)的变化;另一方面,实验通过免疫荧光组织化学方法观察AMPAR/GluR2在L-LTP翻转前后海马CA1区表达的变化。结果显示,L-LTP诱导后2h,HI-PP-LFS可诱导L-LTP的部分翻转(翻转率为61.79%±14.51%)。LTP诱导前、诱导2h后、翻转后PPR均大于1,表现为双脉冲易化(paired-pulse facilitation,PPF),且三者大小顺序为:LTP诱导后LTP翻转后LTP诱导前;在海马CA1区AMPAR/GluR2亚单位的表达方面,对照组、LTP组及LTP翻转组之间没有显著差异。上述结果提示,海马CA1区L-LTP维持与翻转均有突触前机制的参与,但L-LTP诱导与翻转前后AMPAR/GluR2表达没有发生变化。     

Effect of mammogenic hormones on the expression of FGF7, FGF10 and their receptor in mouse mammary gland

To investigate the regulation of estrogen, progesterone and prolactin stimulating the development of mammary gland, the Kunming mice were used as experimental animals in this study. Through the experiment in vitro, the effect of mammogenic hormones were systematically investigated on expression of FGF7 and FGF10 and their receptor in different periods. The results are as follows: in mammary glands of mice, 17 beta-estradiol increased the expression of FGF7; progesterone did not affect the expression of FGF7; prolactin up-regulated the expression of FGF7 significantly in pregnancy and lactation. 17 beta-estradiol increased the expression of FGF10; progesterone and prolactin reduced the expression of FGF10 significantly in virgin; prolactin significantly increased the expression of FGF10 in pregnancy. When 17 beta-estradiol in the body was in relatively high proportion, it would lower the expression of KGFR; while 17 beta-estradiol in the body was in relatively low proportion, it would increase the expression of KGFR. Low concentration of progesterone increased the expression of KGFR and high progesterone did not affect the expression of KGFR. Prolactin increased the expression of KGFR significantly in pregnancy and lactation.     

Age-related effects of the neuromodulator D-serine on neurotransmission and synaptic potentiation in the CA1 hippocampal area of the rat

The effects of the co-agonist of the N-methyl-D-aspartate receptor (NMDAr) D-serine on glutamatergic neurotransmission and synaptic potentiation were studied in the CA1 hippocampal field of young (3-5 months old) and aged (25-27 months old) Sprague-Dawley rats using ex vivo extracellular electrophysiological recording techniques. Exogenous d-serine depressed fast neurotransmission mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate subtype of glutamate receptors in young but not in aged rats by acting on inhibitory glycinergic interneurons. In contrast, D-serine dose-dependently enhanced NMDAr-mediated synaptic responses in both groups of animals, but with a larger magnitude in aged rats, thus preventing the age-related decrease in NMDAr activation. D-serine also increased the magnitude of long-term potentiation in aged but not in young rats. Finally, D-serine levels were dramatically reduced in hippocampal tissues of aged rats. Taken together, these results indicate a weaker activation of the NMDAr glycine modulatory site by endogenous D-serine in aged animals, which accounts for a reduced NMDAr contribution to synaptic plasticity in ageing.     

Effect of mammogenic hormones on the expression of dFGF7, FGF10 and their receptor in mouse mammary gland

To investigate the regulation of estrogen, progesterone and prolactin stimulating the development of mammary gland, the Kunming mice were used as experimental animals in this study.Through the ex-periment in vitro, the effect of mammogenic hormones were systematically investigated on expression of FGF7 and FGF10 and their receptor in different periods.The results are as follows:in mammary glands of mice, 17 beta-estradiol increased the expression of FGF7;progesterone did not affect the expression of FGF7;prolactin up-regulated the expression of FGF7 significantly in pregnancy and lac-tation.17 beta-estradiol increased the expression of FGF10;progesterone and prolactin reduced the expression of FGF10 significantly in virgin;prolactin significantly increased the expression of FGF10 in pregnancy.When 17 beta-estradiol in the body was in relatively high proportion, it would lower the ex-pression of KGFR;while 17 beta-estradiol in the body was in relatively low proportion, it would increase the expression of KGFR.Low concentration of progesterone increased the expression of KGFR and high progesterone did not affect the expression of KGFR.Prolactin increased the expression of KGFR significantly in pregnancy and lactation.     

迷走神经刺激对难治性癫痫大鼠海马神经炎性反应及α7nAChR表达的影响*

目的: 探讨迷走神经刺激(VNS)对难治性癫痫(IE)模型大鼠海马神经炎性反应及α7nAChR表达的影响。方法: 80只成年雄性SD大鼠,SPF级,随机分为对照组、模型组、VNS组、甲基牛扁亭(MLA)+VNS组,其中对照组与MLA+VNS组分别20只,模型组与VNS组因模型制作失败与动物死亡,分别剩下15只和14只。除对照组之外,其余各组皆通过腹腔注射皮罗卡品建立氯化锂-皮罗卡品IE大鼠模型。对照组仅分离迷走神经,不采取电刺激;模型组不采取任何干预措施;VNS组在模型制作成功后7 d采取VNS,连续4周;MLA+VNS组先侧脑室给药MLA(3.4 μg/μl,5 μl),然后给予VNS,连续4周。观察并记录各组大鼠癫痫发作的次数与持续时间的变化;然后断头处死大鼠,快速分离海马并制备10%组织匀浆,离心并提取上清液,通过分光光度法测定上清液中AChE、ChAT活性;ELISA法检测TNF-ɑ、IL-6和IL-1β表达;Western blot检测海马组织α7nAChR蛋白表达;免疫荧光染色法检测海马组织α7nAChR与小胶质细胞共表达。结果: ①通过VNS治疗4周后,大鼠癫痫发作的频率以及持续的时间都明显低于模型组(P<0.01);MLA阻断后在给予VNS,大鼠癫痫发作的频率以及持续的时间也明显低于模型组,但高于VNS组(P<0.01)。②与对照组比较,模型组大鼠海马组织ChAT表达明显下降,AChE表达明显升高(P<0.01);与模型组比较,VNS组与MLA+VNS组大鼠海马组织ChAT表达明显升高,AChE表达明显降低(P< 0.01);与VNS组比较,MLA+VNS组大鼠海马组织ChAT、AChE表达无明显变化(P>0.05)。③与对照组比较,模型组大鼠海马组织TNF-ɑ、IL-6和IL-1β表达明显升高(P<0.01);与模型组比较,VNS组大鼠海马组织TNF-ɑ、IL-6和IL-1β表达明显降低(P<0.01);与VNS组比较,MLA+VNS组大鼠海马组织TNF-ɑ、IL-6和IL-1β表达明显升高(P<0.01)。④与对照组比较,模型组大鼠海马组织以及小胶质细胞上α7nAChR表达明显降低(P<0.01);与模型组比较,VNS组大鼠海马组织以及小胶质细胞上α7nAChR表达明显上调(P<0.01);与VNS组比较,MLA+VNS组海马小胶质细胞上共表达α7nAChR数量明显减少(P<0.01)。结论: VNS对IE大鼠有明显的治疗作用,其机制可能是通过直接激活海马小胶质细胞CAP,抑制海马神经炎性反应来实现的。     

Rapid compensatory changes in the expression of EAAT-3 and GAT-1 transporters during seizures in cells of the CA1 and dentate gyrus

Background

Epilepsy is a neurological disorder produced by an imbalance between excitatory and inhibitory neurotransmission, in which transporters of both glutamate and GABA have been implicated. Hence, at different times after local administration of the convulsive drug 4-aminopyridine (4-AP) we analyzed the expression of EAAT-3 and GAT-1 transporter proteins in cells of the CA1 and dentate gyrus.

Methods

Dual immunofluorescence was used to detect the co-localization of transporters and a neuronal marker. In parallel, EEG recordings were performed and convulsive behavior was rated using a modified Racine Scale.

Results

By 60 min after 4-AP injection, EAAT-3/NeuN co-labelling had increased in dentate granule cells and decreased in CA1 pyramidal cells. In the latter, this decrease persisted for up to 180 min after 4-AP administration. In both the DG and CA1, the number of GAT-1 labeled cells increased 60 min after 4-AP administration, although by 180 min GAT-1 labeled cells decreased in the DG alone. The increase in EAAT-3/NeuN colabelling in DG was correlated with maximum epileptiform activity and convulsive behavior.

Conclusions

These findings suggest that a compensatory mechanism exists to protect against acute seizures induced by 4-AP, whereby EAAT-3/NeuN cells is rapidly up regulated in order to enhance the removal of glutamate from the extrasynaptic space, and attenuating seizure activity.     

Expression and intracellular localization of TBC1D9, a Rab GTPase-accelerating protein,in mouse testes

Membrane trafficking in male germ cells contributes to their development via cell morphological changes and acrosome formation. TBC family proteins work as Rab GTPase accelerating proteins (GAPs), which negatively regulate Rab proteins, to mediate membrane trafficking. In this study, we analyzed the expression of a Rab GAP, TBC1D9, in mouse organs and the intracellular localization of the gene products. Tbc1d9 showed abundant expression in adult mice testis. We found that the Tbc1d9 mRNA was expressed in primary and secondary spermatocytes, and that the TBC1D9 protein was expressed in spermatocytes and round spermatids. In 293T cells, TBC1D9-GFP proteins were localized in the endosome and Golgi apparatus. Compartments that were positive for the constitutive active mutants of Rab7 and Rab9 were also positive for TBC1D9 isoform 1. In addition, TBC1D9 proteins were associated with Rab7 and Rab9, respectively. These results indicate that TBC1D9 is expressed mainly in spermatocytes, and suggest that TBC1D9 regulates membrane trafficking pathways related to Rab9- or Rab7-positive vesicles.     

Activated mitogen-activated protein kinase kinase 7 redistributes to the cytosol and binds to Jun N-terminal kinase-interacting protein 1 involving oxidative stress during early reperfusion in rat hippocampal CA1 region

Mitogen-activated protein kinase kinase (MKK) 7, a specific upstream activator of Jun N-terminal kinases (JNKs) in the stress-activated protein kinase (SAPK)/JNK signaling pathway, plays an important role in response to global cerebral ischemia. We investigated the subcellular localization of activated (phosphorylated) MKK (p-MKK) 7 using western blotting, immunoprecipitation and immunohistochemistry analysis in rat hippocampus. Transient forebrain ischemia was induced by the four-vessel occlusion method on Sprague-Dawley rats. Our results showed that both protein expression and activation of MKK7 were increased rapidly with peaks at 10 min of reperfusion in the nucleus of the hippocampal CA1 region. Simultaneously, in the cytosol activated MKK7 enhanced gradually and peaked at 30 min of reperfusion. In addition, we also detected JNK-interacting protein (JIP) 1, which accumulated in the perinuclear region of neurons at 30 min of reperfusion. Interestingly, at the same time-point the binding of JIP-1 to p-MKK7 reached a maximum. Consequently, we concluded that MKK7 was rapidly activated and then translocated from the nucleus to the cytosol depending on its activation in the hippocampal CA1 region. To further elucidate the possible mechanism of MKK7 activation and translocation, the antioxidant N-acetylcysteine was injected into the rats 20 min before ischemia. The result showed that the levels of MKK7 activation, translocation and binding of p-MKK7 to JIP-1 were obviously limited by N-acetylcysteine in the cytosol at 30 min after reperfusion. The findings suggested that MKK7 activation, translocation and binding to JIP-1 were closely associated with reactive oxygen species and might play a pivotal role in the activation of the JNK signaling pathway in brain ischemic injury.     

Block of P2X7 receptors could partly reverse the delayed neuronal death in area CA1 of the hippocampus after transient global cerebral ischemia

Transient global ischemia (which closely resembles clinical situations such as cardiac arrest, near drowning or severe systemic hypotension during surgical procedures), often induces delayed neuronal death in the brain, especially in the hippocampal CA1 region. The mechanism of ischemia/reperfusion (I/R) injury is not fully understood. In this study, we have shown that the P2X7 receptor antagonist, BBG, reduced delayed neuronal death in the hippocampal CA1 region after I/R injury; P2X7 receptor expression levels increased before delayed neuronal death after I/R injury; inhibition of the P2X7 receptor reduced I/R-induced microglial microvesicle-like components, IL-1β expression, P38 phosphorylation, and glial activation in hippocampal CA1 region after I/R injury. These results indicate that antagonism of the P2X7 receptor and signaling pathways of microglial MV shedding, such as src-protein tyrosine kinase, P38 MAP kinase and A-SMase, might be a promising therapeutic strategy for clinical treatment of transient global cerebral I/R injury.     

En1 and Wnt7a interact with Dkk1 during limb development in the mouse

Wnt signaling plays an essential role in induction and development of the limb. Missing digits are one consequence of the reduced Wnt signaling in Wnt7a null mice, while extra digits result from excess Wnt signaling in mice null for the Wnt antagonist Dkk1. The extra digits and expanded apical ectodermal ridge (AER) of Dkk1-deficient mice closely resemble En1 null mice. To evaluate the in vivo interaction between En1 and the canonical Wnt signaling pathway, we generated double and triple mutants combining the hypomorphic doubleridge allele of Dkk1 with null alleles of En1 and Wnt7a. Reducing Dkk1 expression in Dkk1d/+Wnt7a-/- double mutants prevented digit loss, indicating that Wnt7a acts through the canonical pathway during limb development. Reducing Dkk1 levels in Dkk1d/dEn1-/- double mutants resulted in severe phenotypes not seen in either single mutant, including fused bones in the autopod, extensive defects of the zeugopod, and loss of the ischial bone. The subsequent elimination of Wnt7a in Dkk1d/dEn1-/-Wnt7a-/- triple mutants resulted in correction of most, but not all, of these defects. The failure of Wnt7a inactivation to completely correct the limb defects of Dkk1d/dEn1-/- double mutants indicates that Wnt7a is not the only gene regulated by En1 during development of the mouse limb.     

8-[2-(2-pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid stimulates GABA release from interneurons projecting to CA1 pyramidal neurons in the rat hippocampus via pre-synaptic alpha7 acetylcholine receptors

Nicotinic acetylcholine (ACh) receptors, such as alpha7, alpha3beta4 and alpha4beta2 receptors in the hippocampus, are suggested to modulate neurotransmitter release. 8-[2-(2-Pentyl-cyclopropylmethyl)-cyclopropyl]-octanoic acid (DCP-LA) (100 nM), a linoleic acid derivative, potentiated responses of alpha7, alpha3beta4 and alpha4beta2 ACh receptors expressed in Xenopus oocytes that are blocked by 3-(1-[dimethylaminopropyl] indol-3-yl)-4-[indol-3-yl] maleimide (GF109203X), a selective inhibitor of protein kinase C (PKC), except for alpha3beta4 ACh receptors. DCP-LA enhanced the nicotine-triggered release of GABA from rat hippocampal slices in the presence of tetrodotoxin in a bell-shaped dose-dependent manner at concentrations ranging from 10 nM to 10 microM, although DCP-LA by itself had no effect on GABA release. The DCP-LA action was inhibited by GF109203X or alpha-bungarotoxin, an inhibitor of alpha7 ACh receptors, but not by mecamylamine or dihydro-beta-erithroidine, an inhibitor of alpha3beta4 and alpha4beta2 ACh receptors. A similar effect on GABA release was obtained with 12-O-tetradecanoylphorbol 13-acetate, a PKC activator. DCP-LA (100 nM) also enhanced GABA release triggered by choline, an agonist of alpha7 ACh receptors, but not 3-[2(s)-azetidinylmethoxy] pyridine, an agonist of alpha4beta2 ACh receptors. In addition, DCP-LA (100 nM) increased the rate of nicotine-triggered GABA(A) receptor-mediated miniature inhibitory post-synaptic currents, monitored from CA1 pyramidal neurons of rat hippocampal slices, and the effect was also inhibited by GF109203X or alpha-bungarotoxin but not by mecamylamine. Thus, the results of the present study indicate that DCP-LA stimulates GABA release by enhancing activity of pre-synaptic alpha7 ACh receptors present on the GABAergic terminals of interneurons that transmit to CA1 pyramidal neurons via a PKC pathway.