Subgroups of luteinizing hormone-releasing hormone perikarya defined by computer analyses in the basal forebrain of intact female rats.

Abstract

The hypothesis that the basal forebrain population of LHRH perikarya is composed of heterogeneous subgroups was examined in this study. We used three-dimensional computerized reconstruction to examine populations of LHRH-immunopositive neurons detected in noncolchicine treated cycling female rats. Perikarya were detected with two antisera capable of detecting LHRH decapeptide within larger mol wt species, i.e. Millar's (RM) 1076 and Arimura's (AA) 419. No immunopositive perikarya were detected with antiserum AA 422, which requires the fully processed decapeptide for binding. A more broadly distributed population of LHRH neurons was detected in females killed on proestrus than in females killed on estrus or the other days of the cycle. These relationships were observed with both antisera, RM 1076 and AA 419. Subgroups of cells were clearly defined when the population of LHRH neurons detected on proestrus was simultaneously displayed with the population detected on estrus. Strikingly similar subgroups were revealed by simultaneous displays of populations of LHRH neurons detected by the antisera RM 1076 and AA 419 in proestrous females. This study revealed a three-dimensional onion skin-like laminar organization of LHRH subgroups expanding from the ventricle outward laterally and from the diagonal band of Broca to the hypothalamus caudally. We propose that these subgroups vary in their metabolic activity of biosynthesis, processing, transport, or release of LHRH in relation to the proestrous preovulatory release of LH.

Oestrogen Receptor‐α and ‐β Immunoreactivity in Gonadotropin‐Releasing Hormone Neurones after Ovariectomy and Chronic Exposure to Oestradiol

“…The overall average number of neurones counted was 90 per animal. This number represents the neurones counted in only 10% of the sections, and thus fits with estimates of approximately 1000–1200 GnRH neurones in the intact female rat brain (32). This is greater than that in the nonacrolein fixed sections, and is most likely due to the increased sensitivity attained with acrolein.…”

Physiology of the Adult Gonadotropin-Releasing Hormone Neuronal Network

“…The one exception has been with regard to the GnRH neurons that express c-Fos at the time of the surge. [703][704][705] Together, these observations suggest that a functionally distinct subpopulation within the GnRH population is located preferentially around the OVLT and is involved in the generation of the GnRH surge. 205 In the rat and mouse, these cFos-expressing GnRH neurons are found predominantly, but not exclusively, in the vicinity of the OVLT, 17,481 where gonadal steroids exert their most profound effects upon GnRH biosynthesis.…”

A Confocal Microscopic Study of Synaptic Inputs to Gonadotropin-Releasing Hormone Cells in Mouse Brain: Regional Differences and Enhancement by Estrogen

“…Computerized three-dimensional reconstruction of the GnRH cell distribution in the basal forebrain across the estrous cycle in rats revealed distinct subgroups within the system [12]. In female rats, activation of approximately 40% of the GnRH cells located primarily in the OVLT-POA occurs during the steroid-induced [13]and proestrous [14]LH surges, as revealed by the induction of immunoreactivity for Fos.…”