Distributions of periventricular projections of the paraventricular nucleus to the median eminence and arcuate nucleus

Neuronal projections from the periventricular subnucleus of the hypothalamic paraventricular nucleus to the median eminence and the arcuate nucleus were investigated in the rat by the anterograde tract-tracer, Phaseolus vulgaris leucoagglutinin. The vast majority of labeled fibers coursed ventrally along the third ventricle and distributed in the external layer of the median eminence bilaterally, with ipsilateral predominance moving caudalwards. Periventricular fibers also terminated in the arcuate nucleus, but this innervation was exclusively ipsilateral.