Stimulatory Role of Substance P on Gonadotropin Release in Ovariectomized Rats

Abstract

Substance P (SP) has been shown to be present in the hypothalamus and anterior pituitary. To evaluate a possible physiological role of endogenous SP in the control of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release, specific antiserum against SP (anti-SP) was injected intraventricularly (3 µl into the third ventricle) or intravenously (50 or 200 µl) into conscious, ovariectomized (OVX) rats. Third ventricular injection of the antiserum induced a significant decrease in both plasma LH and FSH levels when compared to values in control animals injected with normal rabbit serum (p < 0.01 and p < 0.025, respectively). The effect was observed within 10 min and levels remained suppressed for 60 min. In contrast, intravenous injection of large doses of anti-SP had no effect on the release of both hormones. In order to confirm the stimulatory effect of SP itself, synthetic SP was injected intravenously and intraventricularly into estrogen-primed (E-primed), OVX rats. Synthetic SP dramatically stimulated LH release, but not FSH release when injected either intravenously or intraventricularly at doses of 10 and 50 µg (p < 0.001, p < 0.005 vs. control, respectively). To investigate any direct action of SP on gonadotropin release from the anterior pituitary gland, synthetic SP was incubated with dispersed anterior piutitary cells harvested from E-primed OVX rats. SP did not affect the release of gonadotropins in vitro. These results indicate that endogenous hypothalamic SP exerts a tonic stimulatory hypothalamic control of basal gonadotropin release in OVX rats.

The Effect of Interleukin-2 on the Release of Gonadotropin and Prolactin in Vivo and in Vitro.

“…It is not surprising that the inhibitory effect of IL-2 on LH release may also be mediated by EOP systems because IL-2 exerts its central effects via EOP systems as described earlier. The failure of FSH release to decrease following the intraventricular injection of IL-2 in our study is probably accounted for by the relative insensitivity of FSH release as compared to that of LH [18].…”

“…Seven days before the experiment, a 23-gauge stainless steel cannula (17 mm in length) was implanted in the third ventricle of OVX rats as described earlier [18]. A mandril was inserted into each cannula to prevent its obstruction.…”

Interaction between substance P and gastrin-releasing peptide on thyrotropin secretion by rat pituitary in vitro

“…Our study establishes that substance P has a direct stimulatory effect at the pituitary level. The fact that Arisawa et al (18) did not find any effect of SP on pituitary cells cultured overnight might be related to differences in the in vitro systems utilized or to different times of incubation. Vijayan and McCann (16) also did not find any effect of SP on TSH secretion using a methodological approach similar to ours, however, they studied ovariectomized female rats.…”

“…Substance P injected into the lateral ventricle of female Rhesus monkey increased prolactin and decreased growth hormone concentrations in serum (15), while in the rat these effects were variable, perhaps depending on the concentration employed (16)(17)(18)(19)(20). The effect on LH is controversial and depends on the species studied, the route of administration and sex-steroid hormonal status (16)(17)(18)21). SP decreased ACTH secretion and stimulated arginine-vasopressin secretion in rats (22).…”

Administration of an Antagonist of Neurokinin Receptors 1, 2, and 3 Results in Reproductive Tract Changes in Beagle Dogs, but Not Rats

“…However, different results, involving either stimulation or inhibition of LH secretion by the pituitary gland, have been achieved in rat studies by adjusting the route of NK administration, whether systemic, intraventricular or by use of in vitro isolated pituitary gland preparations (Vijayan and McCann, 1979;Arisawa et al, 1990;Battmann et al, 1991;Duval et al, 1996aDuval et al, , 1998. In addition, conflicting effects of NK administration on LH secretion have been reported as a consequence of manipulating the gonadal steroid environment of both male and female rats in different test systems (DePalatis et al, 1985;Kalra et al, 1992;Duval et al, 1998).…”