HISTAMINERGIC ACTIVITY REMAINS NORMAL IN PORTACAVAL SHUNTED RATS

The steady-state level of histamine (HA) in the hypothalamus of portoc aval shunted (PCA) rats was significantly higher than control values, while the concentration of N(tau)-methylhistamine (t-MeHA) was unaffec ted. Two hours after administration of the monoamine oxidase inhibitor , pargyline (PG, 80 mg/kg i.p.), the tissue concentration of t-MeHA wa s increased and the net increase was almost the same for PCA and sham operated rats. It appears, therefore, that there is no difference in t he activity of histaminergic neurons between PCA and control rats.