ALTERED HISTAMINE-H3 BINDING IN RAT FOREBRAIN AFTER RESERPINE TREATMENT

Groups of 6 rats were treated for 5 days with either reserpine hydrochloride (5 mg/kg i.p., per diem), or saline. Regional binding of the histamine H-3 agonist N(alpha)-(H-3]methyl-histamine ([H-3]NAMH) was determined in forebrain sections by quantitative autoradiography and Scatchard analysis. Highest maximal binding was in nucleus accumbens (107 +/- 18 fmol/mg) and corpus striatum (58 +/- 9 fmol/mg), where the apparent affinity was close to 4 nM. Maximal binding of [H-3]NAMH in the insular cortex (39 +/- 6 fmol/mg) was higher than in other cortical areas examined. Reserpine treatment produced a 50% decrease in both the B(max) and the apparent K(d) in the corpus striatum and nucleus accumbens, but binding parameters in the cortex and septum were unaltered. Therefore, the response of H-3 receptors in rat forebrain to reserpine treatment for 5 days was regionally heterogenous such that maximal [H-3]NAMH binding was typically higher in insular cortex (36 +/- 6 fmol/mg) than in corpus striatum (24 +/- 3 fmol/mg) of reserpine-treated rats.