Identification and characterization of estrogen receptor ?-containing neurons projecting to the vicinity of the gonadotropin-releasing hormone perikarya in the rostral preoptic area of the rat

Abstract

Gonadal steroids exert a powerful regulatory influence upon the functioning of gonadotropin‐releasing hormone (GnRH) neurons despite the apparent absence of gonadal steroid receptors in these cells. By using retrograde‐tracing techniques combined with dual‐labeling immunocytochemistry, we show here that distinct populations of estrogen receptor alpha (ERα)‐containing neurons located in the hypothalamus and caudal brainstem project to the vicinity of the GnRH perikarya located in the rostral preoptic area (rPOA). The strongest estrogen‐receptive afferent projection to this area originated from neurons located in the anteroventral periventricular and medial preoptic nuclei of the preoptic area. Approximately 50% of arcuate nucleus neurons projecting to the rPOA were demonstrated to synthesize either neuropeptide Y or β‐endorphin, but little evidence was found for ERα immunoreactivity in either of these specific subpopulations. Over 80% of all tyrosine hydroxylase‐expressing neurons in the arcuate nucleus expressed ERα, but none projected to the rPOA. In the caudal brainstem, the A1 and A2 norepinephrine neurons comprised nearly all of the retrogradely labeled neurons. However, only the A2 afferents expressed ERα immunoreactivity, whereas the A1 afferents coexpressed neuropeptide Y. These observations, combined with the anterograde labeling data of others, provide neuroanatomical evidence for the existence of specific estrogen‐receptive neuronal cell populations that project to the rPOA and may be involved in the estrogen‐dependent transsynaptic regulation of GnRH neurons in the rat. J. Comp. Neurol. 411:346–358, 1999. © 1999 Wiley‐Liss, Inc.

Suppression of Vasoactive Intestinal Polypeptide in the Suprachiasmatic Nucleus Leads to Aging-Like Alterations in cAMP Rhythms and Activation of Gonadotropin-Releasing Hormone Neurons

“…The AVPV serves as a nodal relay station where information on steroidal milieu is communicated to GnRH neurons (Simerly et al, 1990;Simerly, 1998;Simonian et al, 1999). We show that the SCN sends circadian signals directly to the OVLT and rMPN areas of the brain that contain a subpopulation of GnRH neurons that are dedicated to regulating the cyclic timing of GnRH-LH surges.…”

Dual-Phenotype GABA/Glutamate Neurons in Adult Preoptic Area: Sexual Dimorphism and Function

“…The strongest ER-containing projections to GnRH neurons comes from the AVPV region (Simonian et al, 1999). In view of our finding that dual-phenotype GABA/glutamate neurons contain most, if not all, ER␣ expression in the AVPV, it seemed likely that dual-phenotype terminals from this nucleus comprise the projections.…”

“…We performed three ICC studies with laser confocal analysis. First, we examined whether GABAergic and glutamatergic vesicles were colocalized in the rPOA, a major projection field of ER-containing neurons in the AVPV (Simonian et al, 1999) and a region that contains abundant GnRH neurons (OVX rats; n ϭ 5). Second, we tested whether rPOA terminals that contained both GABAergic and glutamatergic vesicles had synaptic specializations as indicated by the presence of synaptophysin (SYN) (Wiedenmann and Franke, 1985) (OVX rats; n ϭ 5).…”

“…Lesions of the AVPV (Wiegand et al, 1980;Wiegand and Terasawa, 1982;Ronnekleiv and Kelly, 1986; or microimplants of antiestrogen placed into the region block luteinizing hormone (LH) surge release. Furthermore, the AVPV provides the majority of ER␣-containing cells that innervate the rostral POA (rPOA), where most GnRH neurons participating in the LH surge reside (Simonian et al, 1999). Finally, the AVPV receives inputs from numerous brain regions that convey sensory and autonomic signals relevant to reproduction (Simerly, 1998).…”

Regulation of the neuroendocrine reproductive axis by kisspeptin-GPR54 signaling

“…Areas where kisspeptin neurons reside, such as the Arc and AVPV, are known to send projections to the medial preoptic area, where there is an abundance of GnRH cell bodies (Canteras et al 1994, Simonian et al 1999. Kisspeptin-containing fibers project to these same areas (Brailoiu et al 2005), and indeed, kisspeptin fibers appear in close approximation to GnRH neurons (Kinoshita et al 2005).…”