Immunocytochemical Localization of LHRH in Axons and Nerve Terminals of the Rat Median Eminence

Abstract

Summary

Cytoimmunological localization of LHRH-containing axons and terminals in the median eminence of male rats was achieved with a potent anti-LHRH antiserum and subsequent labeling with a second, peroxidase- or fluorescein isothiocyanate-bound, anti-gamma globulin antibody. The distribution of peptidergic fibers extends from the rostral part of the median eminence, immediately behind the retrochiasmatic area, to the region of the pituitary stalk. In the external zone of the rostral median eminence and close to the stalk, the antigenic material appears in the form of large granules accumulated around blood vessels. This distribution suggests that such granules are likely to represent axon terminals, in contrast to axonal processes containing smaller granular elements lined up radially or longitudinally underneath the external zone.

Specific LHRH labeling could not be visualized at the level of perikarya, even in castrated and colchicine-treated animals; however, nonspecific staining was eventually observed within cell bodies or fiber tracts throughout the hypothalamus as well as other brain structures, particularly after colchicine treatment and incubation with relatively high concentrations of antisera. It thus appears that, under our experimental conditions, only distal portions of LHRH producing neurons can be detected by im-munocytochemistry.