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Showing 2 results for Komaki

Abdolrahman Sarihi, Alireza Komaki, Tadaharu Tsumoto,
Volume 12, Issue 2 (Summer 2008)
Abstract

Introduction: (S)- 3,5-Dihydroxyphenylglycine (DHPG) is an agonist for group I metabotropic glutamate receptors. DHPG-induced synaptic depression of excitatory synapses on hippocampal pyramidal neurons is well known model for synaptic plasticity studies. The aim of the present study was to examine the effects of DHPG superfusion on excitatory synapses on pyramidal and fast-spiking GABAergic cells (FS-GABA) of layer II/III of mice visual cortex. Methods: Effects of DHPG was examined in visual cortical slices of GAD67-GFP knock-in mice using whole-cell recordings of excitatory postsynaptic potentials (EPSPs) in layer II/III cells evoked by layer IV stimulation. In part of experiments, long term potentiation (LTP) was induced by theta burst stimulation (TBS) paired with postsynaptic depolarization. Results: DHPG induced potentiation of EPSPs of FS-GABA neurons in dose- and use-dependent manners but it has no effect on pyramidal cell excitatory synapses. An antagonist for type 5 metabotropic glutamate receptors (mGluR5) blocked DHPG-induced LTP, while an antagonist for mGluR1 was not effective. This potentiation and TBS-induced LTP occluded each other. Conclusion: Based on important role of FS-GABA cells in cortical neuronal circuit, mGlur5-dependent LTP may play a role in, enhancement or maintenance of synchronized activity of cortical pyramidal neurons.
Bahareh Bashirgonbadi, Alireza Komaki, Sima Nasri, Siamak Shahidi, Abdolrahman Sarihi,
Volume 16, Issue 3 (Fall 2012)
Abstract

Introduction: There is currently a debate over the interaction between Ca2+ channels and cannabinoid system on learning and memory processing. In this study, we examined the effect of acute injection of cannabinoid agonist (Win- 55212-2) (Win) or antagonist (AM251), following chronic injection of verapamil, as a L-type Ca2+ channels blocker, on passive avoidance (PA) test in male Wistar rats. Methods: Male Wistar rats weighing 200-250 g were used. The animals were randomly divided into two main groups. Firstly, these two groups were treated with i.p injection of verapamil (25 mg/kg) or saline for 13 days (once daily). Before PA training, each group was divided into three subgroups, which received verapamil (or saline), Win (1 mg/kg) or AM251 (1 mg/kg). Then, PA training (acquisition test) was performed and retrieval test was done 24 h after the training. Results: The results showed that Win as a cannabinoid receptor agonist and verapamil as an L-type Ca2+ channels blocker decreased the acquisition and retrieval of PA task, but AM251 as a cannabinoid antagonist improved PA task. Meanwhile, acute use of an antagonist, simultaneous with verapamil, prevent verapamil induced PA impairment effect. Conclusion: The results of the present study indicate that acute injection of cannabinoid agonist and chronic injection of verapamil decrease memory in the PA task, whereas acute injection of cannabinoid antagonist has the opposite effect on memory. Furthermore, there is an interaction between functions of L-type Ca2+ channels and cannabinoid system on learning and memory.

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