Nitric Oxide in the Ventromedial Nucleus of the Hypothalamus Mediates Action of Estrogen on Goat Ingestive Behavior.

Abstract

Abstract. To examine the hypothesis that whether nitric oxide (NO) in the brain is involved in actions of estrogen on reproduction and ingestion in ruminant species, three experiments were conducted using ovariectomized (ovx) or ovx plus estradiol (E) treated goats. In experiment 1, distributions of cells containing estrogen receptor (ER) or NO synthase (NOS) in the hypothalamus were determined immunohistochemically, which revealed that both ER and NOS positive cells were localized abundantly in the ventromedial nucleus of the hypothalamus (VMH). In experiment 2, several doses of sodium nitroprusside (SNP), an NO donor, was administered into the unilateral VMH of ovx goats immediately before the presentation of food. Injection of 1.5 µg SNP resulted in an abrupt decrease in food intake during the first 60-min of a 240-min feeding period. However, higher doses of SNP had no effect on food intake. In experiment 3, on the other hand, N Gmonomethyl-L-arginine (L-NMMA), a NOS inhibitor, was injected into the bilateral VMH of animals which had been treated with E. Although following the vehicle injection food intake was significantly suppressed by E as was seen in the VMH intact animal, this E-induced decrease in food intake was prevented by administering L-NMMA. This NOS inhibitor, on the other hand, altered neither the timing of the luteinizing hormone surge nor estrous behavior. These data suggest that NO in the VMH is involved in mediation of suppressive effect of E on ingestive behavior in the goat. Key words: Ingestive behavior, Estrogen, Nitric oxide (NO), Ventromedial nucleus of the hypothalamus (VMH), Goat.(J. Reprod. Dev. 44: [149][150][151][152][153][154][155][156][157][158][159] 1998) e have shown that administration of physiological levels of estrogen induces reduction fied, the ventromedial nucleus of the hypothalamus (VMH) seems to be one of the most plausible targets for estrogen to simultaneously alter reproductive and ingestive functions. The VMH is thought to be an important center for controlling reproductive [1] as well as ingestive [2] behaviors, and it has been demonstrated in a number of species [3][4][5][6] that this nucleus contains estrogen receptor (ER) in abundant. Previous observations that direct application of estrogen to the VMH of food intake and rumination at the time of estrus behavior manifestation and the luteinizing hormone (LH) surge in ovariectomized (ovx) goats [Aoyama et al., submitted]. Although sites of these estrogen actions in the brain are yet to be identi-W

Effects of Estrogen on Growth Hormone Pulsatility in Peripheral Blood and Neuropeptide Profiles in the Cerebrospinal Fluid of Goats

“…Estradiol thus appears to modulate the activity of GHRH neurons through an indirect pathway in sheep. In goats, ERα was expressed in the arcuate nucleus (ARC) and ventromedial nucleus (VMN) of hypothalamus [42], but whether GHRH neurons express ERα remains unknown. Further studies are needed to determine how estrogen induces GHRH neural activity.…”

Sex differences in stress responses to transportation in goats: Effects of gonadal hormones

“…Three capsules each containing 0.1 g of Es made of silicon tubing (3.55 mm i.d., 4.65 mm o.d., 40 mm length: AS ONE, Osaka, Japan) were implanted into one animal. Published reports indicate that this method restores the blood concentration of Es to that of intact females (Aoyama et al . 1998a,b).…”