Spatiotemporal patterns of activity in an intact mammalian network with single-cell resolution: Optical studies of nicotinic activity in an enteric plexus

Multiple Site Optical Recording of Transmembrane Voltage (MSORTV) has been used to measure, continuously and simultaneously, the spontaneous electrica l activity from all of the neurons in individual ganglia or up to five inte rconnected ganglia of the submucous plexus of the guinea pig small intestin e. These are the first optical recordings of electrical activity with singl e-cell resolution from a mammalian nervous system. They are used to investi gate the effects of acute and chronic application of nicotine on the firing patterns of this neural network containing important cholinergic component s. After washout of acutely applied nicotine, the firing rates of selected neurons were dramatically elevated. These results suggest that nAChRs that reversibly desensitize after exposure to nicotine may be responsible for th e enhancement of activity that is observed after a brief application of thi s agonist. In addition, immunostaining with monoclonal antibodies was used to localize alpha 3/alpha 5, alpha 7, and beta 2 nAChR subunits, and the re sults demonstrate the prevalence of alpha 3/alpha 5. It is this alpha 3-con taining nAChR subtype that probably accounts for most of the excess activit y elicited by nicotine application.