AUDITORY CORTICAL-NEURONS IN-VITRO - INITIAL PHARMACOLOGICAL STUDIES

Dissociated embryonic tissue from murine auditory cortex formed sponta neously active monolayer networks in culture that were maintained for up to 113 days in vitro (div). As a first step in determining whether neurons retain histiotypic properties, we subjected a set of 10 cultur es to a sequence of 4 synaptically active substances. The test sequenc e consisted of 50 mu M bicuculline, 10 mu M strychnine, 5 mu M NMDA, a nd 20 mu M GABA. Recordings were made for 5-30 min under each conditio n followed by complete medium changes. Six to 14 channels with the bes t signal-to-noise ratios were selected for analysis that consisted of continual chart recordings of integrated burst data and further analys is of short data segments after digitizing and processing. All network s showed spontaneous activity, but had greatly varying native activity ranging from organized, quasi-periodic bursting on all channels to mo re complex spatio-temporal patterns with less coordination among chann els. Bicuculline triggered oscillatory activity, simplified bursting, increased burst amplitude, and enhanced burst regularity among electro des. Strychnine also changed the burst activity to a simpler pattern a nd enhanced the burst amplitude, indicating presence of glycine recept ors in cortical tissue. Application of NMDA increased burst frequencie s, but reduced burst regularity and coordination among channels. 20 mu M of GABA inhibited all bursting activity in the networks. These resu lts suggest that monolayer networks cultured on multi-electrode arrays retain some basic histiotypic pharmacological responses and may provi de useful platforms for the study of network dynamics in the auditory cortex.