HISTAMINE-CONTAINING NEURONS IN APLYSIA

Abstract

This chapter examines the role of histamine in the central nervous system of the invertebrate mollusk Aplysia californica. Histamine plays an important role in synaptic neurotransmission. The evidence favoring a neuronal function for histamine is almost entirely biochemical. Although there is currently a great deal of interest regarding the function of brain histamine, the evidence for its role in neurotransmission remains decidedly suggestive. There is an abundance of correlative cellular physiological, neuropharmacological, and biochemical data pertaining to established neurotransmitters in the central nervous system of Aplysia californica, making it the desired animal for studying the role of histamine as a synaptic transmitter. The nervous system of Aplysia consists of eight major ganglia that are linked together by connectives, which contain axons that carry information between ganglia. This amine is released by them as a neurotransmitter. Histamine in Aplysia ganglia are about 10 to 15 times larger than those found in the vertebrate central nervous system. Also, histamine might be predominantly localized to connective tissue rather than nervous tissue per se. Therefore, at present, we have no reasonable metabolic explanation for the presence of low concentrations of histamine in certain Aplysia neurons.