GABA-T-POSITIVE NEURONS IN THE RAT SUPRAOPTIC NUCLEUS AS REVEALED BY A PHARMACO-HISTOCHEMICAL METHOD WITH GABACULINE

Abstract

The pharmaco-histochemical method with gabaculine treatment for selectively detecting the enzyme 4-aminobutyrate: 2-oxoglutarate (EC. 2.6.1.19.: GABA-T) in neuronal perikarya was applied to the rat supraoptic nucleus (SO) to detect GABA-T-intensive, presumably GABAergic neurons in and around the SO, and if possible, to examine their relationship to neurosecretory neurons.
A significant number of medium-sized GABA-T-intensive neurons were detected in the dorsal part, while more numerous, small, moderately GABA-T-positive neurons were detected in the ventral part of the perinuclear zone just dorsal to the SO. Inside the SO, no GABA-T-intensive intrinsic neurons were detected, although a few small, mildly GABA-T-positive ones were detected in a few cases. No projections of these GABA-T-intensiven eurons to the SO were detected. The unreactive cell bodies of some neurosecretory neurons located in the dorsal margin of the SO as well as in discrete groups scattered throughout the SO were surrounded by granular reaction products for GABA-T.
The results strongly suggest that the medium-sized GABA-T-intensive neurons in the perinuclear zone send their axons to the SO, where they richly divide into many branches which surround the cell bodies of some oxytocin and vasopressin cells with abundant GABA-T-positivea xon terminals.