Regional variations of 5HT concentrations in Rorasg (staggerer) mutants.

Ataxic Rora(sg) (staggerer) mouse mutants, containing a deletion of the Rora gene which encodes a retinoid-like nuclear receptor, were compared to non-ataxic controls for concentrations of 5-hydroxytryptamine (HT), its main metabolite (5-hydroxy-indole acetic acid, 5HIAA), and its precursor (tryptophan) in cerebellum, brainstem, and forebrain. In Rora(sg) cerebellum, 5HT concentrations increased relative to controls, while tryptophan concentrations decreased. 5HIAA concentrations increased in mutant cerebellum and brainstem, but the 5HIAA/5HT ratio declined only in cerebellum. These results indicate that 5HT turnover decreased in cerebellum of an ataxic mutant, perhaps indicative of presynaptic accumulation and compromised neurotransmission and susceptible to be modified by 5HT pharmacotherapy.