Increases in antidromic latency of neurohypophyseal neurons during sustained activation

Antidromic action potentials were recorded from rat paraventricular nucleus (PVN) and supraoptic nucleus neurons following electrical stimulation of the pituitary stalk. Increases in stimulation frequency to 10 or 20 Hz caused progressive increases in antidromic latency and, often, failure of the antidromic potential within 1 min. Similar changes were observed in antidromically invaded PVN neurons in a hypothalamic slice; this condition could be mimicked at 1 Hz stimulation when the potassium concentration was increased in the perfusate. These results suggest that the ionic environment of axons can influence their ability to transmit impulses.