Diencephalic sites responsive to prostaglandin E2 facilitation of sexual receptivity in estrogen-primed ovariectomized rats

Estrogen receptors regulate the estrous behavior induced by progestins, peptides, and prostaglandin E2

The role of classical estrogen receptors (ERs) in priming female reproductive behavior has been studied previously; however, the participation of this receptor during activation of estrous behavior has not been extensively studied. The purpose of this work was to test the possibility that the facilitation of lordosis behavior in estrogen-primed rats by progesterone (P) and its 5α- and 5β-reduced metabolites, gonadotropin-releasing hormone (GnRH), leptin, prostaglandin E2 (PGE2) and vagino-cervical stimulation (VCS) involves interactions with classical ERs by using the selective ER modulator, tamoxifen. To further assess the role of ERs, we also explored the effects of the pure ER antagonist, ICI182780 (ICI), on estrous behavior induced by P and GnRH. Ovariectomized, estrogen-primed rats (5μg estradiol benzoate 40h earlier) were injected intraventricularly with the above-mentioned compounds, or they received VCS. All compounds and VCS effectively facilitated estrous behavior when tested at 60, 120 or 240min after infusion or application of VCS. Intraventricular infusion of tamoxifen (5μg), 30min before, significantly attenuated estrous behaviors induced in estradiol-primed rats by P, most of its 5α- and 5β-reduced metabolites, GnRH, and PGE2, but not by VCS. Although there was a trend for reduction, tamoxifen did not significantly decrease lordosis in females treated with 5β-pregnan-3,20-dione. ICI also inhibited lordosis behavior induced by P and GnRH at some testing intervals. These results suggest that activation of classical ERs participates in the triggering effects on estrous behavior induced by agents with different chemical structures that do not bind directly to ERs.

Nitric oxide and ERK/MAPK mediation of estrous behavior induced by GnRH, PGE2 and db-cAMP in rats

We tested the hypothesis that GnRH, PGE2 and db-cAMP act via the nitric oxide (NO)-cGMP and MAPK pathways to facilitate estrous behavior (lordosis and proceptivity) in estradiol-primed female rats. Estradiol-primed rats received intracerebroventricular (icv) infusions of pharmacological antagonists of NO synthase (L-NAME), NO-dependent soluble guanylyl cyclase (ODQ), protein kinase G (KT5823), or the ERK1/2 inhibitor PD98059 15 min before icv administration of 50 ng of GnRH, 1 microg of PGE2 or 1 microg of db-cAMP. Icv infusions of GnRH, PGE2 and db-cAMP enhanced estrous behavior at 1 and 2 h after drug administration. Both L-NAME and ODQ blocked the estrous behavior induced by GnRH, PGE2 and db-cAMP at some of the times tested. The protein kinase G inhibitor KT5823 reduced PGE2 and db-cAMP facilitation of estrous behavior but did not affect the behavioral response to GnRH. In contrast, PD98059 blocked the estrous behavior induced by all three compounds. These data support the hypothesis that the NO-cGMP and ERK/MAPK pathways are involved in the lordosis and proceptive behaviors induced by GnRH, PGE2 and db-cAMP. However, cGMP mediation of GnRH-facilitated estrous behavior is independent of protein kinase G.

Lordosis facilitation by LHRH, PGE2 or db-cAMP requires activation of the kinase A signaling pathway in estrogen primed rats

Dose-response curves for lordosis and proceptive behaviors were obtained for luteinizing hormone releasing hormone (LHRH), prostaglandin E2 (PGE2) and dibutyryl cyclic AMP (db-cAMP), by infusing them in the right lateral ventricle (i.c.v.) of ovariectomized (OVX) estradiol benzoate (E2B; 2 microg) treated rats. Two dose levels, one producing the maximal effect and the other one producing a submaximal response (approximately ED50) were selected for testing the capacity of Rp-cAMPS, a kinase A blocker, to modify the behavioral response to the three compounds. I.c.v. injections of Rp-cAMPS, significantly depressed both lordosis and proceptive responses induced by LHRH, PGE2 and db-cAMP. The results show that these agents use the cAMP-kinase A signaling pathway to elicit their stimulating effect on estrous behavior in the rat.

Reduction of lipocalin-type prostaglandin D synthase in the preoptic area of female mice mimics estradiol effects on arousal and sex behavior

In female rodents, sleep and activity levels fluctuate over the estrous cycle. When estradiol (E2) levels are highest, sleep is reduced whereas locomotion is increased. The preoptic area (POA) is a key site for estrogenic regulation of these functions. However, molecular mechanisms by which E2 acts to reduce sleep and increase activity are unclear. Recently, we demonstrated a twofold reduction in lipocalin-type prostaglandin D synthase (L-PGDS) transcript levels, after E2 treatment, in the ventrolateral POA (VLPO), a putative sleep-active nucleus. Catalytic activity of L-PGDS produces PGD2, an endogenous somnogen. Thus, we hypothesized that decreases in PGD2 in the VLPO may contribute to the generalized arousal mediated by estrogens. To test this, we infused (i) antisense oligonucleotides (oligos), containing locked nucleic acid moieties (an improved technology), targeted to L-PGDS mRNA, (ii) scrambled sequence control oligos, or (iii) saline vehicle into the VLPO of ovariectomized female mice treated with E2 or oil. Arousal states and activity levels were assessed in response to a series of sensory stimuli (vestibular, olfactory, and somatosensory). The vestibular stimulus, which was administered first, resulted in the strongest responses and elicited significantly different responses among the groups: all groups in the E2 cohort demonstrated increases in overall home cage activity and duration of that activity compared with the oil-treated control groups. As predicted from E2 suppression of L-PGDS transcript levels, the responses of the locked nucleic acid antisense oligo-treated animals from the oil cohort did not differ from the E2-treated groups, such that they also demonstrated increases in activity and duration of activity compared with their controls. Thus, reducing L-PGDS in the VLPO of oil-treated females mimicked the effect of E2 on activity and arousal and represents a unique molecular pathway through which E2 may modulate these functions.

Mating increases plasma levels of prostaglandin F2 alpha in female garter snakes

Plasma levels of prostaglandin F2 alpha (PGF2 alpha) in female red-sided garter snakes (Thamnophis sirtalis parietalis) were measured at intervals after mating or exposure to males. PGF2 alpha levels increased significantly within 15 minutes of mating and peaked 6-24 hr after mating. Females that did not mate, but received similar amounts of male courtship, had levels of PGF2 alpha significantly lower than those of females that mated. These results extend previous findings that unmated female garter snakes injected with PGF2 alpha exhibit sexual behavior characteristic of females that have mated. Together these data indicate that female garter snakes elaborate PGF2 alpha in response to stimuli associated with mating and that PGF2 alpha has a functional role in inducing post-mating declines in sexual behavior of this species.

Clonidine inhibits female spawning behavior in ovulated and prostaglandin-treated goldfish

Previous studies have indicated that female spawning behavior in goldfish is stimulated by prostaglandin (PG) synthesized in the reproductive tract shortly after ovulation and acting within the brain. In this study, clonidine inhibited PG-induced spawning behavior of nonovulated female goldfish in a dose-dependent manner and also inhibited spawning of ovulated goldfish. In male goldfish, clonidine also inhibited PG-induced female spawning behavior but did not affect male spawning behavior. The results provide further support for a role of endogenous PG in female spawning behavior of goldfish and are consistent with the findings [15] that clonidine antagonizes the action of PG on sexual behavior in the female guinea pig.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC, CNS depressants and stimulants, hormones, inorganic ions, gases, 2,4-DNP and miscellaneous agents

This survey concludes a series of complications of data from the literature, primarily published since 1965, on thermoregulatory effects of antipyretics in afebrile as well as in febrile subjects, LSD and other hallucinogens, cannabinoids, general CNS depressants, CNS stimulants including xanthines, hormones, inorganic ions, gases and fumes, 2,4-dinitrophenol and miscellaneous agents including capsaicin, cardiac glycosides, chemotherapeutic agents, cinchona alkaloids, cyclic nucleotides, cycloheximide, 2-deoxy-D-glucose, dimethylsulfoxide, insecticides, local anesthetics, poly I:poly C, spermidine and spermine, sugars, toxins and transport inhibitors. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary agents.

Prostaglandins, clonidine and sexual receptivity in the guinea pig

Prostaglandins E1 and F2 alpha suppressed lordosis in ovariectomized guinea pigs brought into estrus with estradiol benzoate and progesterone. Pretreatment with clonidine prevented this action of the prostaglandins, but if the animals were first given prostaglandin and allowed to go out of estrus, then clonidine did not restore lordosis. In a previous study it was found that the abbreviation of estrus induced by copulation was also blocked by clonidine, again only if it were given before the inhibitory treatment. These results suggest tht prostaglandin, perhaps released from the female reproductive tract, could mediate the inhibitory effect of copulation, and radioimmunoassays of prostaglandin F2 alpha and its principal metabolite PGFM revealed substantial elevations in the concentrations of these materials in trunk blood after copulation. We discuss the possibility that prostaglandins may suppress sexual receptivity by interfering with an alpha-adrenergic mechanism.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents

This survey, the second in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of cholinergic agonists and antagonists, histamine and H1- and H2-receptor antagonists, narcotic analgesics and antagonists in both non-tolerant and tolerant subjects and of prostaglandins and related agents. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

Debilitating interaction of adrenalectomy and intrahypothalamic implants of prostaglandin E2 upon open-field activity levels and sexual receptivity in estrogen-primed ovariectomized rats

A group of estrogen-primed, ovariectomized rats was adrenalectomized and tested for sexual receptivity following hypothalamic implantations of PGE2. The combination of PGE2 and adrenalectomy led to severe debilitation as manifested by greatly reduced open-field activity scores and inhibition of estrogen and progesterone induced sexual receptivity. Neither exogenous progesterone nor corticosterone was able to restore these behaviors to normal levels. A mechanism involving PGE2 and adrenalectomy-induced transient ischemia was discussed as a possible cause of the debilitation.