Thyroliberin blocks the potassium A-current in neurons in the respiratory center of adult rats in vitro.

Thyroliberin is a neuropeptide with marked respiratory activity. The neuronal mechanisms underlying this activity were addressed in experiments on transverse slices of brainstem from adult rats in conditions of membrane potential clamping to study effect effects of thyroliberin (10 nM) on the potassium A-current in neurons of two areas of the respiratory center--the ventrolateral areas of the solitary tract nucleus and the pre-Betzinger complex. The A-current, seen in all study neurons in the respiratory center, was partially and reversibly blocked by thyroliberin. A significant reduction in the amplitude of the current was accompanied by an increase in the inactivation constant. The effect of thyroliberin on the amplitude of the A-current was analogous to that of 5 mM 4-aminopyridine. These results show that the stimulatory effects of thyroliberin at the level of respiratory center neurons is at least partly explained by its ability to block the potassium A-current.