Immunohistochemistry of Luteinizing Hormone-Releasing Hormone-Producing Neurons of the Vertebrates

Observations of various LH- RH-reactive axonal tract endings exhibit that besides its major, direct, prehypophysotrophic action through the hypophyseoportal system, LH-RH may also be distributed by the blood of the vascular organ of the lamina terminalis, as neuroendocrine integrator neurons.

Abstract

The hypothalamic topography of the luteinizing hormone-releasing hormone (LH-RH) reaction gives rise to the hypothalamoinfundibular tract and to the preopticoterminal LH-RH tract, fits closely with the hypothalamic LH-RH topography determined by biological or biochemical assays, by radioimmunoassays, or after hypothalamic disconnection. The modifications of immunoreactivity of the hypothalamoinfundibular and the preopticoterminal LH-RH tracts, as well as of the extrahypophyseal LH-RH pathway describe that the reactive material shown is in fact LH-RH, which is, at least in part, synthesized in the reaction, possibly in the form of a high-molecular-weight precursor. Observations of various LH-RH-reactive axonal tract endings exhibit that besides its major, direct, prehypophysotrophic action through the hypophyseoportal system, LH-RH may also be distributed by the blood of the vascular organ of the lamina terminalis. LH-RH neurons are thus seen not only as classical neurosecretory cells with solely pericapillary axon endings but also as neurons with multiple, portal, and extrahypophyseal efferents, as neuroendocrine integrator neurons.