Whitney Laboratory, University of Florida, St Augustine 32086.
In two species of lobster, application of the biogenic amine, histamine (HA), to the soma of olfactory receptor cells suppressed both spontaneous and odour-evoked activity, as shown by electrophysiological recording from single cells. The action of HA was graded, reversible, specific to HA, and had a threshold between 0.1 and 1 mumol l-1. HA increased the conductance of the membrane, primarily to chloride ions. The vertebrate HA receptor antagonist, cimetidine, and the nicotinic receptor antagonist, d-tubocurarine, but not other known vertebrate HA receptor antagonists, reversibly blocked the action of HA. These results suggest that a histaminergic mechanism modulates stimulus-response coupling in lobster olfactory receptor cells and potentially implicate a novel HA receptor, pharmacologically similar to the one recently described in the visual system of flies.