High resolution radioautographic identification of [3H]GABA labeled neurons in the rat nucleus raphe dorsalis.

Following intraventricular administration of [3H]GABA into the lateral ventricle of the rat radioautography demonstrates the presence of labeled cell bodies and fibers within the nucleus raphe dorsalis (NRD). Pharmacological controls suggest that labeled perikarya whose diameter does not exceed 10 micrometer and which are not probably more than ten in the entire NRD could be GABAergic. The effects of 5,7-dihydroxytryptamine (5,7-DHT) pretreatment support the hypothesis that labeled fibers could belong at least to two populations: ones being probably serotonergic and the others being possibly GABAergic. These results are in good agreement with the existence of an intrinsic GABAergic system within the rat NRD.