ETHANOL-INDUCED CHANGES IN THE SPONTANEOUS ACTIVITY OF SINGLE UNITS IN THE HIPPOCAMPUS OF THE AWAKE RAT - DOSE-RESPONSE STUDY

The spontaneous firing rates of single units in the dorsal hippocampus of semi-restrained rats chronically prepared with bundles of fine wire nichrome microelectrodes, were monitored during an ethanol challenge. Doses (7) of a 25% wt/vol ethanol solution were administered i.p. to all rats, each dose being given on a separate day with an interdose interval of at least 48 h. Each ethanol injection was preceded by 2 control recording periods: baseline and saline injection. Units (61) from 27 animals were studied with 7-10 units tested at each dose. Single cells in the hippocampus are sensitive to ethanol, and this sensitivity was reflected by a depression in firing rate is dose-dependent with larger doses producing greater degrees of depression. The simultaneously recorded EEG indicated a marked bias in frontal cortical activity towards high amplitude slow waves while the hippocampal activity showed less marked but more varied changes. The hippocampus was among those structures whose activity and function were particularly sensitive to ethanol, a profile of a structure''s response to ethanol can be obtained when a sample of neurons was tested at a spectrum of doses.