PATCH-CLAMP STUDY OF HISTAMINE ACTIVATED POTASSIUM CURRENTS ON RABBITOLFACTORY-BULB NEURONS

Effects of histamine, histamine agonists and antagonists on steady sta te current in principal neurons and interneurons were investigated in thin slices from the olfactory bulb of newborn rabbits with the nystat in perforated patch-clamp technique and local pipette application. No change in steady state current was observed in mitral cells. In most o f the periglomerular, juxtaglomerular and granular cells, however, H-1 -receptor activation caused an outward current; a similar effect, but mostly not on the same neurons was elicited by 8-bromo-cyclic-AMP. The se currents were reversed at the potassium equilibrium potential and b locked by apamin and therefore probably represent calcium sensitive po tassium currents. H-2-receptor activation caused an inward current whi ch also reversed at the potassium equilibrium potential, indicating bl ock of a potassium current. Specific H-3-receptor activation and cycli c GMP were ineffective. Histamine usually caused a combined effect beg inning with an inward current. Histaminergic neurons fire with changes in behavioural state and can, by the described mechanisms, markedly i nfluence signal processing in the olfactory bulb.