5-HT1A RECEPTOR AGONIST REVERSES ADRENALECTOMY-INDUCED LOSS OF GRANULE NEURONAL MORPHOLOGY IN THE RAT DENTATE GYRUS

Adrenal steroids are important for maintaining neuronal maturation in the adult rats. Two weeks after bilateral adrenalectomy (ADX), hippoca mpal MAP-2 (microtubule associated protein-2) and calbindin immunoreac tivity (IR) decreased in the molecular layer of the superior blade of the dentate gyrus. The molecular and granular cell layer at the latera l tip of the superior blade decreased in width by 32% and 50%, respect ively. The granule neurons showed reduced staining with Niss1 and an a nti-calbindin antibody. These changes suggested a loss of the mature n euronal morphology. In this same localized regions, two glial proteins , glial fibrillary acidic protein (GFAP) and S-100 beta showed dramati cally reduced immunoreactivity. These effects induced by ADX were redu ced within 72 hrs by ipsapirone (1 mg/kg), a 5HT(1A) receptor agonist. Loss of adult neuronal morphology by ADX, and reversal by the 5HT(1A) agonist, may be evidence of the trophic importance of the 5HT(1A) rec eptor in granule neurons of hippocampus.