Physiological and pharmacological evidence for histamine as a neurotransmitter in the olfactory CNS of the spiny lobster.

Perfusing histamine (HA, 0.1 microM-1 mM) into the brain of the spiny lobster reversibly altered the spontaneous activity in 24 (86%) of 28 morphologically unidentified, odor-responsive interneurons. The effects of HA were dose-dependent and could be selectively and reversibly antagonized by cimetidine, a vertebrate H2 antagonist, suggesting that the action of HA in the central nervous system (CNS) was mediated by a receptor pharmacologically similar to an HA receptor expressed by lobster olfactory receptor cells. Perfusing HA into the brain also reversibly altered the spontaneous and/or odor-evoked activity of 6 (67%) of 9 morphologically identified, odor responsive interneurons that arborized in the olfactory lobe (OL). These results extend previous evidence from our lab that the OL contains HA-immunoreactive interneurons and that OL tissue can synthesize HA from its precursor and further implicate HA as a putative neurotransmitter in the olfactory CNS of the spiny lobster.