Chapter 16 - Histamine

Abstract

Publisher Summary Histamine is a signaling molecule in the stomach, skin, immune, and nervous systems. The posterior hypothala­mus is the sole source of histamine-containing neurons that innervate the whole central nervous system and are active exclusively during walking. Three of the four known metabo­tropic histamine receptors are widely expressed in the brain. H1 and H2 are mostly excitatory; H3 is an inhibitory auto and heteroreceptor. It is now clear that histamine is an important regulator of several brain functions and is released from central nervous system neurons. Mutual interactions with other aminergic and peptidergic systems form a network that links basic homeo­static and higher brain functions including sleep–waking regulation, energy administration, feeding, drinking, synaptic plasticity, learning, and memory. Chemically, histamine is 2-(4-imidazolyl) ethylamine. The ethylamine “backbone” is a common feature of many of the amine transmitters (e.g., dopamine, norepinephrine, and sero­tonin). Histamine also induces antinociceptive (pain-relieving) responses in animals after microinjection into several brain regions. The chapter also summarizes the major mechanisms for the syn­thesis and metabolism of histamine, as well as the characteristic features of known hista­mine receptors in mammals.