DISTRIBUTION OF NADPHDIAPHORASE AND CALBINDIN-D28K NEURONS IN THE LATERAL SEPTAL AREA OF THE GUINEA-PIG, WITH SPECIAL REFERENCE TO THE ENKEPHALINERGIC HYPOTHALAMO-SEPTAL TRACT

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd) histoc hemical techniques were used to identify neurons synthesizing nitric o xide in the lateral septum of the guinea pig. Double immunocytochemica l procedures were used to detect neurons immunoreactive for calbindin- D28k and enkephalinergic fibers which project to the lateral septum. T he present data demonstrate that (1) the neurons containing NADPH diap horase and the neurons immunoreactive for calbindin-D28k are observed in discrete regions of the lateral septum; (2) these populations overl ap in various areas of the lateral septum including its dorsal and med iolateral parts; (3) NADPH diaphorase and calbindin-D28k are colocaliz ed in neurons located in the overlapping areas; (4) neurons identified by the presence of calbindin-D28k, NADPH diaphorase or both substance s, are surrounded by enkephalinergic fibers. These observations indica te the chemical heterogeneity of the lateral septum and suggest that t he enkephalinergic hypothalamo-septal tract does not preferentially co ntact a subpopulation of neurons.