Expression of the H3 receptor in the developing CNS and brown fat suggests novel roles for histamine

Histamine and histamine receptors have been implicated in signaling mechanisms in developmental processes in the brain and peripheral organs. Pharmacological studies have also implied that the histamine H(3) receptor, in addition to acting as a presynaptic auto- and heteroreceptor in the central nervous system, is active in peripheral tissues. We show that detectable histamine H(3)-receptor expression during development and in adult rat is restricted to specific areas of the brain and to adipocytes and the capillary network in brown adipose tissue. Histamine H(3)-receptor mRNA expression was not detected in other internal organs studied, or in spinal or sympathetic chain ganglia. These results support a histaminergic involvement in brain development through activation of the histamine H(3) receptor and indicate a possible novel involvement of the histamine H(3) receptor as a mediator of the effects of histamine in thermogenesis in brown adipose tissue.