Activation of pallidal H2 receptors induces catalepsy in Wistar rats: A regulatory role of CRF1 receptors

An increased concentration of histamine was found in the globus pallidus of parkinsonian patients. The role of this abnormality in the development of parkinsonism is unclear. We examined cataleptogenic activity of histamine injected into the globus pallidus (GP); also, the role of H2 receptors in histamine effect was evaluated. Given a possible role of the GP in integration and processing of stress signals, we tested the involvement of CRF1 receptors in the regulation of histamine effect. The experiments were conducted with male Wistar rats, catalepsy was assessed using bar test. The entopeduncular nucleus (EPN) was used as a neuroanatomical control. Intrapallidal injections of histamine (1.0 and 10.0 µg) produced clear cataleptic response whereas intra-EPN injections were ineffective. Histamine-induced catalepsy was dose-dependently attenuated by H2 receptor antagonist ranitidine and CRF1 receptor antagonist NBI 35965. The results suggest the involvement of pallidal H2 and CRF1 receptors in the development of catalepsy in rats. These findings may provide novel insight into the mechanism of parkinsonian-like disorders. In light of the presented data, H2 and CRF1 receptors might be potential targets for therapy of parkinsonism.