Summary on the

We have invest igated the catabol ism of [3H] hista-mine (HA), after intraventr icu lar (i.vt.) administra-tion, in brains of the audiogenic seizure suscept ib le (SS) and res istant (SR) deermouse Peromyscus. Brains of SS mic @ had lower endogenous HA levels an d contained less [JH]-HA 20, 60 and 300 sec after i.vt. [ JH]-~A than did brains of SR deermice. Twenty sec after [JH]-HA, brain [JH] methy lh is tamine (MeHA) levels and the result-ing MeHA ccnvers ion index were found to be increased in the SS animals while later, at 60 and 300 sec, these parameters were found to be decreased. ~There were no SS-SR d i f ferences in the levels of brain [JH] methyl imi-dazoleacet ic acid. The data indicate that SS deermiee catabol ize exogenous HA, at least init ial ly, more rapid-ly than their SR counterparts, conf i rming a like resul