SYNAPTIC ORGANIZATION OF TUBERAL HYPOTHALAMUS IN TISSUE-CULTURE - EFFECTS OF ELECTRICAL-STIMULATION AND BLOCKERS OF SYNAPTIC TRANSMISSION

Poststimulus histograms were used to quantitate effects of focal electrical stimulation on spontaneously active neurons in tuberal hypothalamic tissue cultures. After electrical stimulation, changes in firing patterns were observed in 94 of 108 spontaneously active units. Three possible components were observed: an early excitation, a subsequent inhibition, or a prolonged facilitation. The early, presumably antidromic, activation was resistant to perfusion by Ca2+-free/high-Mg2+ salt solution; later, synaptic effects were abolished. Perfusion of 10-5m picrotoxin reduced or abolished these longer-latency inhibitions in a majority of cells. These results suggest first, that there is a high degree of functional synaptic connection in tuberal hypothalamic tissue cultures, and second, that there exist intrinsic inhibitory interneurons in this region, which utilize γ-aminobutyric acid as their transmitter and are involved in the generation of the normally encountered firing patterns. © 1979.