HISTAMINERGIC PROJECTIONS FROM THE PREMAMMILLARY AND POSTERIOR HYPOTHALAMIC REGION TO THE CAUDATE PUTAMEN COMPLEX IN THE RAT

Immunofluorescence, using antibodies to histamine and to histidine decarboxylase, was combined with retrograde axonal tracing by injecting Granular Blue into the caudate-putamen complex. Evidence is presented for the existence of histaminergic as well as nonhistaminergic projections from the posterior hypothalamus and the premammillary region to the caudate-putamen complex. The majority of the histaminergic neurons projecting to this brain region are localized in the nuclei caudalis magnocellularis and caudalis magnocellularis postmammallaris. Roughly 20-25% of the histaminergic neurons in these cell groups innervate the caudate-putamen complex.