Regional distribution of luteinizing hormone-releasing hormone (LH-RH) in rat brain determined by microdissection and radioimmunoassay.

We have re-examined the distribution of LH-RH in rat brain and in particular those rostral hypothalamic areas reported to contain perikarya by immunocytological techniques. Adult male rats were decapitated and 20 discrete brain structures micro-dissected. Tissue from single rats was homogenized in 50 microliter 0.1 N HCl and 40 microliters of this acid extract was radioimmunoassayed for LH-RH using the R-42 antibody. Low but detectable concentrations which ranged from0.2 to 1.0 pg/micrograms protein were found in the interstitial nucleus of the stria terminalis (ventral aspect), medial preoptic nucleus (dorsal and ventral aspects), lateral preoptic nucleus, anterior hypothalamic nucleus, paraventricular nucleus, ventromedial nucleus (medial and lateral aspects) and the dorsomedial nucleus. Slightly higher concentrations (1.0--4.0 pg/micrograms protein) were measured in a rostral, medial basal corridor made up of the suprachiasmatic preoptic nucleus, the suprachiasmatic nucleus and the retrochiasmatic area. LH-RH was not detected (i.e. less than 0.8 pg/area) in the bed nucleus of the diagonal band of Broca, caudate nucleus, lateral septal nucleus or the cingulate cortex.