[Antidromal identification of hypothalamic neurosecretory cells in the rat]

Characteristics of antidromic action potentials of neurons in hypothalamic paraventricular and supraoptic nuclei were investigated during stimulation of hypothalamo-hypophyseal tract by stimuli of different amplitude and frequency. At tract stimulation with increased strength (1.5-2.5 times threshold) or frequency (above 100/s) discrete changes in antidromic action potential latency as well as variation of the spike fractionation in response to testing stimulus were observed. Leu-enkephaline administration into the third ventricle and intravenous injection of 1M NaCl solution reversibly changed the excitability of the antidromically activated neuron: leu-enkephaline mostly increased the latent period and the threshold of spike generation and decreased their capability to follow the stimulation frequency up to 10 Hz, whereas NaCl produced opposite effects. The data obtained indicate the necessity to take into account the excitability of the neurosecretory cell when using the accepted criteria of their antidromic identification.