Presence of immunoreactive luteinizing hormone in the rat forebrain.

This study demonstrates the presence of immunoreactive LH in rat brain by radioimmunoassay and immunocytochemistry. High levels of radioimmunoassayable LH were identified in the hypothalamus, while significant but lesser quantities were found in the amygdala, septal area, preoptic area, thalamus, caudate nucleus, and hippocampus. Correlative immunocytochemistry localized immunopositive fibers in hypothalamic and several extrahypothalamic brain structures. Immunoreactive cell bodies were seen in colchicine-treated rats in the arcuate nucleus of the hypothalamus. Gel chromatography of hypothalamic extracts revealed that immunoassayable LH coeluted with LH standard and rat pituitary extracts. Possible mechanisms related to the origin and functional neuronal LH are discussed.