PERIVENTRICULAR-HYPOPHYSEAL DOPAMINERGIC-NEURONS INNERVATE THE INTERMEDIATE BUT MOT THE NEURAL LOBE OF THE RAT PITUITARY-GLAND

The purpose of the present study was to determine the relative distrib ution of axon terminals of A(14) periventricular-hypophysial dopaminer gic (PHDA) neurons in the neural and intermediate lobes of the rat pit uitary gland. Discrete unilateral injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) into the periventricular n ucleus resulted in labelling of extensively branched terminal axonal a rbors in the intermediate lobe, but not the neural lobe of the pituita ry gland. In contrast, unilateral injections of PHA-L into the paraven tricular nucleus revealed thick, varicose terminal arborizations conta ining PHA-L in the neural lobe, but not the intermediate lobe. Termina l axonal branches and varicosities containing PHA-L immunoreactivity i n the intermediate lobe were also immunoreactive for tyrosine hydroxyl ase. These results reveal that A(14) PHDA neurons originating in the p eriventricular nucleus of the hypothalamus project axons to the interm ediate lobe of the rat pituitary gland.