Muscarinic excitation of fast-spiking basket cells of rat hippocampal dentate gyrus

• Main Authors: Wei-Chun Yeh, 葉韋均
• Other Authors: Cheng-Chang Lien
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/269ad7

碩士 === 國立陽明大學 === 神經科學研究所 === 97 === Cholinergic transmission is involved in learning- and memory-associated theta (4-10 Hz) -gamma (30-100Hz) oscillations. Although fast-spiking basket cells (BCs) are suggested to be the cellular substrate of gamma oscillations, accumulating studies showed that fast-spiking BCs in the neocortex are unresponsive to cholinergic modulation. In contrast to neocortex, cholinergic effects on fast-spiking BCs in the hippocampus CA1 region have remained elusive. Dentate gyrus is one of gamma oscillators in the hippocampus. In contrast to the neocortex and the CA1 region, the impacts of mAChR activation on excitatory and inhibitory outputs of fast-spiking BCs in the dentate gyrus remain unexplored. Here this study investigated the influence of postsynaptic muscarinic acetylcholine receptor (mAChR) activation on fast-spiking BCs in the dentate gyrus of rat brain slices using patch-clamp whole cell recording. Bath application of mAChR agonist muscarine in the presence of ionotropic glutamate receptor and GABAA receptor blockers strongly depolarized fast-spiking BCs and led them to fire in the theta to gamma range at room temperature and body temperature. In voltage-clamp recording, mAChR activation markedly reduced resting current, which exhibited a reversal potential close to the equilibrium potential for K+ channels. Furthermore, the effect was largely reversed by pirenzepine, the M1 subtype muscarine receptor selective antagonist, suggesting that inhibition of K+ current was mediated through activation of postsynaptic M1 subtype muscarinic receptors. The functional consequences of muscarinic excitation on BCs may provide driving force for these neurons to generate gamma rhythm and thereby enhance cortical performance.