Serotonin reinnervation of the rat organum vasculosum laminae terminalis (OVLT) after 5,7-dihydroxytryptamine deafferentation.

The time course and pattern of serotonin (5-HT) reinnervation in the rat organum vasculosum laminae terminalis (OVLT) following intracerebroventricular administration of 5,7-dihydroxytryptamine were examined by means of [3H]5-HT uptake radioautography. 5-HT axonal varicosities reappeared in the OVLT within 3 months post-lesion. Six months later, they were found to have preferentially reinvested the neurohemal contact area (juxtavascular zone) of the organ. Regenerated terminals further increased in number. At the end of a 16-month survival time, they displayed normal-looking distributional patterns, similar to those of age-matched control animals, and formed new synaptic junctions in the juxtaventricular zone. The cellular mechanisms possibly responsible for 5-HT recovery in the OVLT are discussed.