G. Setalo

Gonadotropin-releasing hormone (GnRH) neurons and pathways in the rat brain

SummaryGonadotropin-releasing hormone (GnRH) neurons and their pathways in the rat brain were localized by immunocytochemistry in 6-to 18-day-old female animals, by use of thick frozen or vibratome sections, and silver-gold intensification of the diaminobenzidine reaction product. GnRH-immunoreactive perikarya were observed in the following regions: olfactory bulb and tubercle, vertical and horizontal limbs of the diagonal band of Broca, medial septum, medial preoptic and suprachiasmatic areas, anterior and lateral hypothalamus, and different regions of the hippocampus (indusium griseum, Ammons horn). In addition to the known GnRH-pathways (preoptico-terminal, preoptico-infundibular, periventricular), we also observed GnRH-immunopositive processes in several major tracts and areas of the brain, including the medial and cortical amygdaloid complex, stria terminalis, stria medullaris thalami, fasciculus retroflexus, medial forebrain bundle, indusium griseum, stria longitudinalis medialis and lateralis, hippocampus, periaqueductal gray of the mesencephalon, and extracerebral regions, such as the lamina cribrosa, nervus terminalis and its associated ganglia. By use of the silver-gold intensification method we present Golgi-like images of GnRH perikarya and their pathways. The possible distribution of efferents from each GnRH cell group is discussed.

Localization of LH-RH-containing Neurons in the Rabbit Brain

In the last three years immunohistologic methods have successfully been used to localize the hypophysiotrophic (releasing and inhibiting) hormones. The first releasing hormone localized by immunohistologic methods in the guinea pig by LEONARDELLI et al. in 1973 was luteinizing hormone-releasing hormone (LH-RH). The species studied so far for the histologic localization of LH-RH include guinea pig, rat, mouse, duck, toad, cat, dog, and greenfinch (BARRY and CARETTE, 1975; SETALO, 1976).