Gonadotropin‐releasing hormone release from the mediobasal hypothalamus of fetal baboons

Abstract

Pulsatile luteinizing-hormone releasing hormone (LHRH) secretion was measured from the mediobasal-suprachiasmatic-preoptic WBH-SCN-POA) region of the hypothalamus from fetal baboons (Pupw unubis) at midgestation (day 100; term = day 184). The entire MBH-SCN-POA (48 +_ 5 mg) was obtained between 1100 and 1200 hours and was immediately placed in icecold phosphate buffer (pH 7.4). The MBH-SCN-POA units were halved at the midline and superfused in parallel at 37.5"C for 5 hours. Then 500 pl of superfusate was collected at 10-minute intervals, and LHRH concentration was measured by radioimmunoassay using the Chen Ramirez antibody. In fetuses of untreated baboons (N = 3), LHRH pulse amplitude (mean +_ SE) was 16.0 f 4.2 pg, with a period of 30 f 1 minute; the average 10-minute output of LHRH was 9.4 f 2.0 pg. In fetal baboons in which the hormonal milieu in the mother was modulated by androstenedione treatment of midpregnancy (N = 3), average LHRH pulse amplitude was 1.7 * 0.3 pg, with a period of 33.5 f 4.9 minutes; the average 10-minute output of LHRH was 1.2 5 0.2 pg. Collectively, these data suggest that as early as midgestation, fetal baboons secrete LHRH in vitro in a pulsatile fashion and with a periodicity of 30-35 minutes. In addition, the decrease in LHRH pulse amplitude and the average 10-minute LHRH output (P < .01, P < .05) in tissue from fetal baboons of mothers in which the normal pattern of steroidogenesis is altered suggest that the output of LHRH systems in the fetus is sensitive to changes in the maternal hormonal milieu.

The electrophysiologic properties of gonadotropin‐releasing hormone neurons

“…142 In mice, connections from the putative pulse generator arcuate kisspeptin neuron and GnRH neurons are established before birth. 143,144 Consistent with this, fetal mediobasal hypothalamic tissue isolated from humans 145 and non-human primates 146 releases GnRH pulses, as do GnRH neurons derived from primate and rodent olfactory placodes. [147][148][149][150] Prenatal preoptic tissue containing GnRH neurons restores LH pulses and/ or gonadal function in models lacking endogenous GnRH, including lesioned adult female monkeys, 151 rats 152 and hpg male mice, 153,154 suggesting that prenatal tissue either has episodic release as an inherent function or can mature into this role.…”