In vitro neurophysiology of identified rat hypothalamic 'neuroendocrine' neurons

Stable synaptic and antidromic electrophysiological recordings were obtained for 10-15 h from identified neurohypophyseal and tuberoinfundibular neurons using an acute explant of rat hypothalamus maintained in vitro through perfusion of the carotid artery with oxygenated artificial media. Synaptic potentials from preoptic and median eminence stimulation were blocked during perfusion with 12 m M Mg++-containing solutions. Antidromic and spontaneous action potentials recorded in neurohypophyseal neurons were followed by a transient after-hyperpolarization of 3-10 mV, due primarily to a brief increase in potassium conductance. Evidence favoring the existence of a synaptic recurrent inhibitory pathway was present in records obtained from tuberoinfundibular neurons, but not from neurohypophyseal cells.