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Find video protocols related to scientific articles indexed in Pubmed.
Lordosis facilitation by leptin in ovariectomized, estrogen-primed rats requires simultaneous or sequential activation of several protein kinase pathways.
Pharmacol. Biochem. Behav.
PUBLISHED: 05-12-2013
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The present study tested the hypothesis that the Janus kinase 2, Src tyrosine kinases, and mitogen-activated protein kinase interact to regulate lordosis behavior induced by leptin in ovariectomized, estrogen-primed rats. The role of protein kinase A and protein kinase C in lordosis facilitation by leptin was also assessed. In experiment 1, the intracerebroventricular administration of leptin to ovariectomized, estradiol-primed rats significantly stimulated lordosis behavior at 1, 2 and 4 h post-injection tests. In experiment 2, the Janus kinase 2 inhibitor AG490, the Src tyrosine kinase inhibitor PP2 and the mitogen-activated protein kinase inhibitor PD98059 were administered into the right lateral ventricle before leptin. The lordosis quotient and the lordosis score induced by leptin were significantly decreased by each of these kinase inhibitors. In experiment 3, we examined the effects of RpcAMPS and bisindolylmaleimide, protein kinase A and protein kinase C inhibitors on the lordosis elicited by leptin administration. Lordosis behavior induced by leptin was significantly decreased by both the protein kinase A and protein kinase C inhibitors at 1 h post-leptin injection. The results confirm that multiple intracellular pathways participate in the expression of lordosis behavior in estrogen-primed rats elicited by leptin.
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The nitric oxide pathway participates in lordosis behavior induced by central administration of leptin.
Neuropeptides
PUBLISHED: 08-04-2011
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Intracerebroventricular (icv) administration of leptin facilitates lordosis behavior in ad libitum-fed, estrogen-primed rats. The cellular mechanism involved in this response is unknown. The present study tested the hypothesis that the nitric oxide-guanylyl cyclase, cGMP-dependent protein kinase (PKG) pathway is involved in the facilitation of lordosis behavior induced by the central administration of leptin. We tested the importance of the nitric oxide/cGMP pathway for lordosis stimulation by either icv infusion of a nitric oxide synthase inhibitor (L-NAME) or a nitric oxide-dependent, soluble guanylyl cyclase inhibitor (ODQ) 30 min before leptin administration (1 ?g). This dose of leptin reliably induced lordosis behavior in ovariectomized estradiol benzoate treated rats. The lordosis induced by leptin at 1 and 2h after infusion was significantly reduced by the previous injection of either L-NAME or by ODQ. Intracerebroventricular infusion of the PKG inhibitor (KT5823) 30 min before leptin infusion, also significantly inhibited the lordosis behavior induced by leptin at 1 and 2h after hormone administration. These data support the hypothesis that the nitric oxide/cGMP/PKG pathway is involved in the facilitation of lordosis by leptin in estrogen-primed female rats.
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Differential effects of progesterone and genital stimulation on sequential inhibition of estrous behavior and progesterone receptor expression in the rat brain.
Brain Res. Bull.
PUBLISHED: 03-25-2011
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The effect of genital stimulation, either by vaginocervical stimulation (VCS) using a calibrated vaginal probe combined with manual flank stimulation (FS), or by mounts performed by the male, on the hypothalamus and preoptic area concentration of the progesterone receptors A (PR-A) and B (PR-B) was assessed in ovariectomized (ovx) estrogen-primed rats. VCS/FS or stimulation provided by male mounts, even without intromission, significantly decreased PR-B concentration in the hypoythalamus. Down regulation of PR produced by genital stimulation was quantitatively similar to that elicited by progesterone (P) administration. Bilateral or unilateral transection of the pelvic or the pudendal nerves prevented down regulation elicited by VCS/FS. Repeated VCS/FS elicited lordosis behavior in most ovx estrogen primed rats, but the lordosis intensity was lower than that observed in response to P. P administered to ovx estrogen primed rats, induced sequential inhibition, i.e., failure to display estrous behavior in response to a second P injection (24h after the initial P injection). VCS/FS failed to elicit sequential inhibition, since rats responded with normal estrous behavior to the second injection of P. This suggests that down regulation by VCS, by contrast with P, failed to inhibit the subpopulation of PR involved in the facilitation of estrous behavior by P.
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Leptin facilitates lordosis behavior through GnRH-1 and progestin receptors in estrogen-primed rats.
Neuropeptides
PUBLISHED: 08-04-2010
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Dose response curves for leptin facilitation of estrous behavior (lordosis and proceptivity) were made by infusing the peptide into the lateral ventricle (icv) of ovariectomized (ovx), ad libitum-fed rats injected 40h previously with 5?g of estradiol benzoate. Leptin doses of 1 and 3?g produced significant lordosis quotient at 60min post-injection, with maximal lordosis being displayed at 120min. Yet the intensity of lordosis was weak, and a high incidence of rejection behaviors was found. Moreover, leptin did not induce significant proceptive behaviors at any dose. The leptin doses of 1 and 3?g were selected for determining whether antide, a GnRH-1 receptor antagonist, or the progestin receptor antagonist RU486 could modify the lordosis response to leptin. Icv injection of either antide or RU486 1h before leptin significantly depressed leptin facilitation of lordosis. The results suggest that leptin stimulates lordosis by releasing GnRH, which in turn activates GnRH-1 and progestin receptors. The physiological role of leptin in the control of estrous behavior remains to be determined.
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A role for Src kinase in progestin facilitation of estrous behavior in estradiol-primed female rats.
Horm Behav
PUBLISHED: 02-09-2010
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This study tested the hypothesis that the Src/Raf/MAPK signaling pathway is involved in the facilitation of the lordosis and proceptive behaviors induced by progesterone (P) and its ring A-reduced metabolites in ovariectomized, estradiol-primed rats. Intraventricular (icv) infusion of PP2 (7.5, 15 and 30 microg), a Src kinase inhibitor, significantly depressed P-dependent estrous behavior (lordosis and proceptivity) in estradiol-primed rats. Icv infusion of 30 microg of PP2 also significantly attenuated estrous behavior induced by the ring A-reduced P metabolites 5 alpha-dihydroprogesterone (5 alpha-DHP) and 5 alpha-pregnan-3alpha-ol-20-one (allopregnanolone). PP2 did not inhibit estrous behavior induced by administration of high doses of estradiol alone to ovariectomized rats. We also assessed if the ventromedial hypothalamus (VMH) is one of the neural sites at which progestins activate Src signaling to facilitate estrous behavior. Bilateral administration of 15 microg of PP2 into the VMH inhibited the stimulation of both lordosis and proceptive behaviors elicited by subcutaneous P administration to estradiol-primed rats. These results suggest that progestins act through Src/Raf/MAPK signaling to initiate estrous behaviors in estrogen-primed rats. This event is one component of the cellular pathways leading to the display of estrous behaviors induced by P and its ring A-reduced metabolites in female rats.
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Motherhood and nursing stimulate c-FOS expression in the rabbit forebrain.
Behav. Neurosci.
PUBLISHED: 07-29-2009
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Mother rabbits nurse once daily with circadian periodicity. The authors investigated brain structures involved in regulating this activity by quantifying c-FOS-immunoreactive (IR) cells in the forebrain of: (1) mothers killed on postpartum Day 1 (PPD 1) after nursing (Group 1) or not given pups (Group 2); (2) mothers killed on PPD 7 after nursing (Group 3) or not given pups on such day (Group 4); (3) unmated virgins (Group 5). Groups 1 through 4 showed similar numbers of c-FOS-IR cells in the preoptic area, an amount around three to fourfold larger than that found in virgins. Nursing increased, on PPD 1 and 7, c-FOS-IR cell number in the lateral septum and paraventricular and supraoptic nuclei. No differences were seen among Groups 1 through 5 in the suprachiasmatic nucleus. In the ventromedial hypothalamus virgins had more c-FOS-IR cells compared with Groups 1 and 2. Results suggest that specific forebrain structures participate in regulating particular aspects of rabbit maternal behavior: the POA and LS seem associated with the establishment of motherhood and the magnocellular nuclei with the occurrence of milk letdown.
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Nitric oxide and ERK/MAPK mediation of estrous behavior induced by GnRH, PGE2 and db-cAMP in rats.
Physiol. Behav.
PUBLISHED: 01-03-2009
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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.
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Src kinase signaling mediates estrous behavior induced by 5?-reduced progestins, GnRH, prostaglandin E2 and vaginocervical stimulation in estrogen-primed rats.
Horm Behav
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The progesterone receptor (PR) is a dual function protein that acts in the nucleus as a transcriptional factor and at the cytoplasm as a scaffold for the Src-MAPK signaling pathway. Several agents lacking affinity for the PR, such as 5?-reduced progestins, GnRH or prostaglandin E(2) (PGE(2)) facilitate estrous behavior in ovariectomized (ovx), estrogen-primed rats yet their action is blocked by the antiprogestin RU486. We hypothesize that these agents act by using the PR-Src-mitogen activated protein kinase alternative pathway. To test this hypothesis we used PP2, a specific inhibitor of the Src kinase family. Intraventricular infusion of 30 ?g of PP2, 30 min before behavioral testing, significantly attenuated estrous behaviors induced in estradiol benzoate (E(2)B)-primed rats by 5?-dihydroprogesterone (5?-DHP), 5?-pregnan-3?-ol-20-one (5?,3?-Pgl), GnRH, PGE(2) and by manual flank/vaginocervical stimulation. These results suggest that the Src signaling system, by activating mitogen-activated protein kinases, participates in the facilitation of estrous behavior in E(2)B-primed rats induced by agents lacking affinity for the PR.
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Bimodal binding and free energy of the progesterone receptor in the induction of female sexual receptivity by progesterone and synthetic progestins.
J. Steroid Biochem. Mol. Biol.
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Synthetic progestins (SPs) are used for regulation of fertility, contraception and hormone replacement therapy. The acetylated medroxyprogesterone (MPA), megestrol (MGA) and chlormadinone (CLA) are related to progesterone (P). Other SPs are 19-nortestosterone derivatives such as: norethisterone (NET), norethynodrel (NED) or the 13-ethyl gonane, levonorgestrel (LNG). We studied MPA, NET, NED and LNG in a dose-response manner to induce sexual receptivity in rats. Results showed that MPA, NET and NED act as partial agonists, with similar or lower potency than P. However, LNG is a full agonist. Additionally, the molecules of MPA, MGA, CLA, NET, NED, LNG, and P, were submitted to computer calculations at ab initio quantum mechanics theory, to obtain their electronic structure and molecular properties. The aim was to correlate their behavioral effect with their physicochemical properties. In addition, the crystals of P, NET and LNG bound to the progesterone receptor (PR) were studied. The PR crystallizes as a dimer forming two monomers (mA and mB), in which Gln725 interacts in either of two possible ways with the C3-carbonyl pharmacophore of progestins. P binds differentially to both PR monomers, while NET binds exclusively as mA and LNG binds only as mB in both monomers with no difference. Energetically, binding of LNG and P to mB, is more favorable than that of NET and P to mA. Consequently, this bimodal mechanism increases the action possibilities of SPs on biological systems. Interestingly, progestin potency depends mostly on local molecular structure and electronic features, prevailing over total molecular properties.
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