Intracellular Ca2+ dynamics of hippocampal interneurons following nicotinic acetylcholine receptor activation

Ca2+ permeability of central nicotinic acetylcholine receptors (nAChRs), especially the alpha 7 subunits, are exceptionally high and this important feature provide a special functional importance for these receptors at the system level. Although studies at the cellular level extensively characterized the molecular properties of Ca2+ influx following nAChR activation, much less is known about the time-related Ca2+ dynamics during nicotine administration in integration units of neurons. Such studies are of particular relevance to understanding in situ nonsynaptic actions of nicotine. Puff ejection of drugs produce a rapid drug delivery and elimination from the cell surface allowing the activation of extrasynaptic receptors within desensitization time-frame. In this report we provide evidence that rapid nicotine application is able to produce irregular Ca2+ transients in the dendrites of stratum radiatum interneurons in the hippocampal CA1 region. Potential components and mechanisms of nAChR-mediated Ca2+ influx are discussed in details to demonstrate the unique feature of activation of nAChRs involved in nonsynaptic function in interneurons as compared to other types of nicotinic activity. (C) 2007 Elsevier Ltd. All rights reserved.