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Cataldo G, Lovric J, Chen CC, Pytte CL, Bodnar RJ. Ventromedial and medial preoptic hypothalamic ibotenic acid lesions potentiate systemic morphine analgesia in female, but not male rats. Behav Brain Res 2010; 214:301-16. [PMID: 20678986 DOI: 10.1016/j.bbr.2010.05.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 05/25/2010] [Accepted: 05/26/2010] [Indexed: 11/30/2022]
Abstract
Sex differences in systemic morphine analgesia occur with male rodents displaying significantly greater analgesic magnitudes and potencies than females. Neonatal androgenization, and to a lesser degree, adult ovariectomy enhance systemic morphine analgesia in female rats, implicating both organizational and activational effects of gonadal hormones. The neuroanatomical circuits sensitive to sex-related hormones by which females display a smaller opiate analgesic effect is not clear, but the ventromedial (VMH) and medial preoptic (MPOA) hypothalamic nuclei are critical in the monitoring of estradiol and other sex hormone levels. To assess the contribution of these nuclei to sex and adult gonadectomy differences in systemic morphine analgesia, intact male, intact female and adult ovariectomized (OVEX) female rats received bilateral saline (SAL) or ibotenic acid (IBO) microinjections into either the VMH or MPOA. Following surgeries, baseline tail-flick latencies over 120 minutes (min) were assessed over 4 days in all nine groups with intact females tested in the estrus phase of their cycle. All animals then received an ascending series of morphine (1.0, 2.5, 5.0, 7.5, 10.0mg/kg) injections 30min prior to the tail-flick test time course with 8-12 day inter-injection intervals between doses. Baseline latencies failed to differ between SAL-treated intact males and females, but were significantly higher in SAL-treated OVEX females. Both VMH IBO and MPOA IBO lesions increased baseline latencies in intact male and female rats, but not in OVEX females. SAL-treated intact males (ED(50)=4.0mg/kg) and SAL-treated OVEX females (ED(50)=3.5mg/kg) displayed significantly greater potencies of systemic morphine analgesia than SAL-treated intact females (ED(50)=6.3mg/kg), confirming previous gender and gonadectomy differences. Neither VMH IBO (ED(50)=3.7 mg/kg) nor MPOA IBO (ED(50)=4.1mg/kg) males differed from SAL-treated males in the potency of systemic morphine analgesia. In contrast, VMH IBO (ED(50)=4.1mg/kg) and MPOA IBO (ED(50)=3.5mg/kg) intact females displayed significantly greater potencies in systemic morphine analgesia than SAL-treated intact females. However, VMH IBO OVEX (ED(50)=3.5mg/kg) and MPOA IBO OVEX (ED(50)=3.9 mg/kg) failed to differ from SAL-treated OVEX females in the potency of systemic morphine analgesia. The magnitudes of systemic morphine analgesia as measured by Maximum Percentage Effect values displayed similar patterns, but lesser degrees, of effects. These data suggest that VMH and MPOA nuclei act to tonically inhibit endogenous pain-inhibitory circuits in the intact female, but not intact male brain, and that removal of circulating gonadal hormones by OVEX and/or excitotoxic destruction of these estrogen receptor accumulating nuclei disinhibit the female analgesic response to systemic morphine.
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Affiliation(s)
- Giuseppe Cataldo
- Department of Psychology, Queens College, City University of New York, Flushing, NY, United States
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2
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Bodnar RJ, Kest B. Sex differences in opioid analgesia, hyperalgesia, tolerance and withdrawal: central mechanisms of action and roles of gonadal hormones. Horm Behav 2010; 58:72-81. [PMID: 19786031 DOI: 10.1016/j.yhbeh.2009.09.012] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 09/11/2009] [Accepted: 09/18/2009] [Indexed: 01/05/2023]
Abstract
This article reviews sex differences in opiate analgesic and related processes as part of a Special Issue in Hormones and Behavior. The research findings on sex differences are organized in the following manner: (a) systemic opioid analgesia across mu, delta and kappa opioid receptor subtypes and drug efficacy at their respective receptors, (b) effects of the activational and organizational roles of gonadal steroid hormones and estrus phase on systemic analgesic responses, (c) sex differences in spinal opioid analgesia, (d) sex differences in supraspinal opioid analgesia and gonadal hormone effects, (e) the contribution of genetic variance to analgesic sex differences, (f) sex differences in opioid-induced hyperalgesia, (g) sex differences in tolerance and withdrawal-dependence effects, and (h) implications for clinical therapies.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology, Queens College, The Graduate Center, City University of New York, NY 11367, USA.
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3
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Cataldo G, Bernal S, Rozengurtel S, Medina K, Bodnar R. Neonatal and Adult Gonadal Hormone Manipulations Enhance Morphine Analgesia Elicited from the Ventrolateral Periaqueductal Gray in Female Rats. Int J Neurosci 2010; 120:265-72. [DOI: 10.3109/00207451003662120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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4
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Shane R, Bernal SY, Rozengurtel S, Bodnar RJ. ESTRUS PHASE DIFFERENCES IN FEMALE RATS IN MORPHINE ANTINOCICEPTION ELICITED FROM THE VENTROLATERAL PERIAQUEDUCTAL GRAY. Int J Neurosci 2009; 117:811-22. [PMID: 17454245 DOI: 10.1080/00207450600910259] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Male rodents display greater systemic morphine antinociception than females which show their most marked effects during late diestrus or proestrus. Morphine (1-2.5 mug) antinociception on the tail-flick test elicited from the ventrolateral periaqueductal gray was examined across estrus phases in female relative to male rats. Morphine antinociception was greatest in magnitude and potency in males followed by females tested during the proestrus phases relative to estrus and met-diestrus. These data confirm morphine's systemic effects, implicate the ventrolateral periaqueductal gray in estrus phase-mediated effects, and underscore the control of the phase of the estrus cycle in examining sex differences in opioid antinociception.
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Affiliation(s)
- Randi Shane
- Department of Social Sciences and Psychology, Bronx Community College, USA
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5
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Kalamatianos T, Grimshaw SE, Poorun R, Hahn JD, Coen CW. Fasting reduces KiSS-1 expression in the anteroventral periventricular nucleus (AVPV): effects of fasting on the expression of KiSS-1 and neuropeptide Y in the AVPV or arcuate nucleus of female rats. J Neuroendocrinol 2008; 20:1089-97. [PMID: 18573184 DOI: 10.1111/j.1365-2826.2008.01757.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Changes in metabolic state, such as those induced by fasting, have profound effects on reproduction. In rats, the time-course over which fasting inhibits luteinising hormone (LH) release is reduced to 48 h by the presence of oestradiol-17beta (E(2)). Hypothalamic kisspeptin plays a key role in mediating the actions of E(2) on gonadotrophin-releasing hormone (GnRH) neurones, and thereby promotes LH release. KiSS-1-expressing neurones are found in the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC). Extensive evidence implicates the AVPV in GnRH release and the ARC in energy balance. The latter nucleus also contains neurones that express neuropeptide Y (NPY), an orexigenic peptide implicated in GnRH control. To elucidate the involvement of kisspeptin and/or NPY in hypothalamic responses to fasting, their expression was quantified by in situ hybridisation histochemistry in ovariectomised rats, with or without E(2) replacement, before and after 48 h of fasting. In the presence of E(2), but not in its absence, the fasting suppressed plasma LH. In the AVPV, the low level of KiSS-1 expression found in the absence of E(2) was unaffected by fasting. By contrast, the elevated level found in the presence of E(2) was suppressed by fasting. Independent of E(2), fasting had no effect on KiSS-1 expression in the ARC, but increased NPY expression at that site. The present study has identified the AVPV as a site at which KiSS-1 expression can be influenced by fasting. The results suggest that inhibition of KiSS-1 expression in the AVPV may be a significant factor in restraining the gonadotrophic axis in response to negative energy balance in the presence of oestrogen. The extent to which the concurrent rise in NPY expression in the ARC may contribute to the suppression of LH release by influencing AVPV kisspeptin neurones, directly or indirectly, or by actions independent of kisspeptin, remains to be established.
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Affiliation(s)
- T Kalamatianos
- Division of Reproduction and Endocrinology, School of Biomedical and Health Sciences, King's College London, London, UK
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6
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Wilson CA, Davies DC. The control of sexual differentiation of the reproductive system and brain. Reproduction 2007; 133:331-59. [PMID: 17307903 DOI: 10.1530/rep-06-0078] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This review summarizes current knowledge of the genetic and hormonal control of sexual differentiation of the reproductive system, brain and brain function. While the chromosomal regulation of sexual differentiation has been understood for over 60 years, the genes involved and their actions on the reproductive system and brain are still under investigation. In 1990, the predicted testicular determining factor was shown to be theSRYgene. However, this discovery has not been followed up by elucidation of the actions of SRY, which may either stimulate a cascade of downstream genes, or inhibit a suppressor gene. The number of other genes known to be involved in sexual differentiation is increasing and the way in which they may interact is discussed. The hormonal control of sexual differentiation is well-established in rodents, in which prenatal androgens masculinize the reproductive tract and perinatal oestradiol (derived from testosterone) masculinizes the brain. In humans, genetic mutations have revealed that it is probably prenatal testosterone that masculinizes both the reproductive system and the brain. Sexual differentiation of brain structures and the way in which steroids induce this differentiation, is an active research area. The multiplicity of steroid actions, which may be specific to individual cell types, demonstrates how a single hormonal regulator, e.g. oestradiol, can exert different and even opposite actions at different sites. This complexity is enhanced by the involvement of neurotransmitters as mediators of steroid hormone actions. In view of current environmental concerns, a brief summary of the effects of endocrine disruptors on sexual differentiation is presented.
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Affiliation(s)
- C A Wilson
- Basic Medical Sciences, Clinical Developmental Sciences, St George's, University of London, Cranmer Terrace, Tooting, London SW17 0RE, UK.
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7
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Hoffman GE, Le WW, Schulterbrandt T, Legan SJ. Estrogen and progesterone do not activate Fos in AVPV or LHRH neurons in male rats. Brain Res 2005; 1054:116-24. [PMID: 16084918 DOI: 10.1016/j.brainres.2005.06.082] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Revised: 06/14/2005] [Accepted: 06/15/2005] [Indexed: 12/16/2022]
Abstract
In rodents, females but not males, in response to escalating levels of estrogen, express a luteinizing hormone (LH) surge that is prompted by a surge in luteinizing hormone-releasing hormone (LHRH). It cannot take place if estrogen-sensitive afferents located in the anteroventral periventricular nucleus (AVPV) are either absent or disabled. Males appear to lack the ability to exhibit an LH surge, but it is unclear what level of the CNS contributes to this dimorphic response. This study was conducted to determine whether estrogen followed by progesterone treatment (E + P) of gonadectomized males evokes Fos activation in LHRH and AVPV neurons as it does in females. The results indicated that, consistent with the males' inability to express an LH surge in response to E + P treatment, LHRH and AVPV neurons in males failed to show increased Fos activation. Examination of neuron nuclear antigen (NeuN, a neuron-specific marker), estrogen receptor (ERalpha) and progesterone receptor (PR) neurons in AVPV neurons indicated that, while essentially all the neurons of the caudal AVPV in males and females are steroid responsive, the male possessed half the number of steroid responsive neurons within the caudal AVPV (where activation of Fos is maximal in females) compared to the female. Together, these data indicate that the male lacks a substantial population of steroid receptive AVPV neurons and is unable to respond to the presence of E and P and activate either AVPV or LHRH neurons.
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Affiliation(s)
- G E Hoffman
- Department of Anatomy and Neurobiology, University of Maryland, School of Medicine, 685 W Baltimore Street, Baltimore, MD 21201, USA.
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8
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Hahn JD, Coen CW. Comparative study of the sources of neuronal projections to the site of gonadotrophin-releasing hormone perikarya and to the anteroventral periventricular nucleus in female rats. J Comp Neurol 2005; 494:190-214. [PMID: 16304687 DOI: 10.1002/cne.20803] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The rat ovulatory cycle is dependent on the preoptic region encompassing the gonadotrophin-releasing hormone (GnRH) perikarya and the anteroventral periventricular nucleus (AVPV). Retrograde tract tracing was used to identify and compare the sources of inputs to these sites in female rats. Within the telencephalon and diencephalon, the incidence of retrograde labelling from both sites was moderate to abundant in the ventral lateral septum, posteromedial bed nucleus of the stria terminalis, amygdalohippocampal area and the periventricular, medial preoptic, anterodorsal preoptic, dorsomedial suprachiasmatic, arcuate, and posterior ventrolateral ventromedial hypothalamic nuclei. In these regions, the incidence of retrograde labelling was either greater from the AVPV than from the GnRH perikarya site or similar from both sites. In the medial amygdaloid, parastrial, striohypothalamic, and ventral premammillary nuclei, the retrograde labelling from the AVPV greatly exceeded the sparse incidence from the GnRH perikarya site. In contrast, retrograde labelling from the GnRH perikarya site predominated in the median preoptic, lateroanterior and dorsomedial hypothalamic nuclei, subparaventricular zone, and retrochiasmatic area; it was abundant in the AVPV. Caudal to the diencephalon, retrograde labelling from either site was sparse, except in the lateral parabrachial nucleus, which displayed a particularly high incidence from the GnRH perikarya site. Other mesencephalic regions labelled from either site included the periaqueductal gray and dorsal and median raphe nuclei. The most caudal labelling was found in the ventrolateral medulla and region of the solitary tract nucleus; this was almost exclusively from the GnRH perikarya site. These findings further elucidate the neuroanatomical connections underlying the control of the ovulatory cycle.
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Affiliation(s)
- Joel D Hahn
- School of Biomedical Sciences, King's College London, SE1 1UL, United Kingdom
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Van Vugt HH, Swarts HJM, Van de Heijning BJM, Van der Beek EM. Centrally Applied Somatostatin Inhibits the Estrogen-Induced Luteinizing Hormone Surge via Hypothalamic Gonadotropin-Releasing Hormone Cell Activation in Female Rats1. Biol Reprod 2004; 71:813-9. [PMID: 15140796 DOI: 10.1095/biolreprod.104.028936] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Overexpression of growth hormone (GH) as well as GH-deficiency dramatically impairs reproductive function. Decreased reproductive function as a result of altered GH release is, at least partially, due to changes at the hypothalamic-pituitary level. We hypothesize that hypothalamic somatostatin (SOM), the inhibiting factor of GH release from the pituitary, may play a central role in the "crosstalk" between the somatotropic and gonadotropic axes. In the present study we investigated the possible effects of a centrally applied SOM analog on the LH surge and the concurrent activation of hypothalamic GnRH neurons in female rats. To this end, female rats were treated with estradiol 2 wk after ovariectomy and were given a single central injection with either the SOM analog, octreotide, or saline just prior to surge onset, after which hourly blood samples were taken to measure LH. Two weeks later, the experimental setup was randomly repeated to collect brains during the anticipated ascending phase of the LH surge. Vibratome sections were subsequently double-stained for GnRH and cFos peptide. Following octreotide treatment, LH surges were significantly attenuated compared to those in saline-treated control females. Also, octreotide treatment significantly decreased the activation of hypothalamic GnRH neurons. These results clearly demonstrate that SOM is able to inhibit LH release, at least in part by decreasing the activation of GnRH neurons. Based on these results, we hypothesize that hypothalamic SOM may be critically involved in the physiological regulation of the proestrus LH surge.
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Affiliation(s)
- Harmke H Van Vugt
- Human and Animal Physiology Group, Wageningen University, 6709 PJ Wageningen, The Netherlands.
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10
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Erskine MS, Lehmann ML, Cameron NM, Polston EK. Co-regulation of female sexual behavior and pregnancy induction: an exploratory synthesis. Behav Brain Res 2004; 153:295-315. [PMID: 15265625 DOI: 10.1016/j.bbr.2004.01.026] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2003] [Revised: 12/20/2003] [Accepted: 01/11/2004] [Indexed: 11/20/2022]
Abstract
This paper will review both new and old data that address the question of whether brain mechanisms involved in reproductive function act in a coordinated way to control female sexual behavior and the induction of pregnancy/pseudopregnancy (P/PSP) by vaginocervical stimulation. Although it is clear that female sexual behavior, including pacing behavior, is important for induction of P/PSP, there has been no concerted effort to examine whether or how common mechanisms may control both functions. Because initiation of P/PSP requires that the female receive vaginocervical stimulation, central mechanisms controlling P/PSP may be modulated by or interactive with those that control female sexual behavior. This paper presents a synthesis of the literature and recent data from our lab for the purpose of examining whether there are interactions between behavioral and neuroendocrine mechanisms which reciprocally influence both reproductive functions.
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Affiliation(s)
- Mary S Erskine
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA.
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11
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Eyigor O, Lin W, Jennes L. Identification of neurones in the female rat hypothalamus that express oestrogen receptor-alpha and vesicular glutamate transporter-2. J Neuroendocrinol 2004; 16:26-31. [PMID: 14962072 DOI: 10.1111/j.1365-2826.2004.01109.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oestrogen exerts its effects in the brain by binding to and activating two members of the nuclear receptor family, oestrogen receptor (ER)-alpha and ER-beta. Evidence suggests that oestrogen-receptive neurones participate in the generation of reproductive behaviours and that they convey the oestrogen message to gonadotropin-releasing hormone (GnRH) neurones. The aim of the present study was to identify the neurochemical phenotype of a subset of oestrogen receptor-expressing neurones. To this aim, we focused on the glutamate neuronal system, which is one of the most important stimulators of GnRH synthesis and release. We used the presence of vesicular glutamate transporter-2 (VGLUT2) mRNA as a specific marker to identify glutamate neurones and employed dual in situ hybridization to localize ERalpha mRNA-(35S-labelling) and VGLUT2 mRNA-(digoxigenin-labelling) expressing neurones within the hypothalamus. The results show that the overall distribution of VGLUT2 mRNA and ERalpha mRNA are consistent with previous data in the literature. Dual-labelled neurones were localized in the ventrolateral part of the ventromedial nucleus where 81.3 +/- 3.4% of the ERalpha mRNA containing neurones expressed VGLUT2 mRNA, in the anteroventral periventricular nucleus (30% colocalization) and in the medial preoptic nucleus (19% colocalization). Only 4.4% of the ERalpha expressing neurones in the arcuate nucleus contained VGLUT2 mRNA. These findings reveal that certain subpopulations of oestrogen-receptive neurones are glutamatergic in select hypothalamic areas that are known to regulate reproductive behaviour and GnRH neurones in the female rat. Thus, the oestrogen signal could be propagated through glutamate neurones to distant sites and influence the activity of the postsynaptic neurones.
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Affiliation(s)
- O Eyigor
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington KY 40536, USA
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12
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Acosta-Martinez M, Etgen AM. The role of delta-opioid receptors in estrogen facilitation of lordosis behavior. Behav Brain Res 2002; 136:93-102. [PMID: 12385794 DOI: 10.1016/s0166-4328(02)00103-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The present study investigated the role of delta-opioid receptors (ORs) in estrogen facilitation of female rat reproductive behavior (lordosis). Infusion of 2 microg of the selective delta-OR agonist [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE), into the third ventricle facilitated lordosis behavior in ovariectomized (OVX) rats injected with estrogen (E) 48 and 24 h before behavioral testing. Pretreatment with the selective delta-OR antagonist naltrindole (NTDL) blocked DPDPE effects on lordosis behavior. Ventricular infusion of NTDL (40 microg) also suppressed lordosis behavior in fully receptive OVX rats primed with both E and progesterone (P). In addition, NTDL blocked lordosis behavior when infused into the ventromedial nucleus of the hypothalamus (VMH) but not into the medial preoptic area (mPOA). Site-specific infusion of DPDPE into the VMH had dose-dependent, dual effects on lordosis behavior. While a very low dose of DPDPE (0.01 microg) facilitated lordosis behavior, a higher dose (1.0 microg) inhibited receptivity in OVX rats primed with E and a low dose (50 microg) of P. We used 3H-DPDPE to measure the density of delta-ORs in OVX rats treated with vehicle or with E by receptor autoradiography. E treatment did not have any effect on the density of DPDPE binding sites in the VMH, mPOA, medial amygdala, or caudate putamen. The behavioral effects of the ligands used in this study suggest that activation of delta-OR in the VMH by endogenous opioids facilitates estrogen-dependent lordosis behavior.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Autoradiography
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Estrogens/pharmacology
- Female
- Microinjections
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Ovariectomy
- Posture
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/physiology
- Sexual Behavior, Animal/drug effects
- Stereotaxic Techniques
- Ventromedial Hypothalamic Nucleus/physiology
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Affiliation(s)
- Maricedes Acosta-Martinez
- Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Forchheimer 113, Bronx, NY 10461, USA.
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13
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Pego-Reigosa R, Coveñas R, Tramu G, Pesini P. Distribution of met-enkephalin immunoreactivity in the diencephalon and the brainstem of the dog. J Chem Neuroanat 2000; 19:243-58. [PMID: 11036241 DOI: 10.1016/s0891-0618(00)00071-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The endogenous opioid system, in particular the enkephalins, has been implicated in a vast array of neurological functions. The dog could be a suitable model for the study of complex interactions between behavioral state and regulatory physiology in which the opioid system appeared to be implicated. Moreover, opiate derivatives are currently used in veterinary clinic and sometimes pharmacologically tested in the dog. However, there are no anatomical data regarding the organization of the opioid system in this species. The present work represents the first attempt to map the distribution of Met(5)-enkephalin-like-immunoreactive (Met-enk-li) cell bodies and fibers in the diencephalon and the brainstem of the dog. In the diencephalon, labeled cells were present in all the mid-line and intralaminar thalamic nuclei; the lateral posterior, pulvinar and suprageniculate nuclei; the ventral nucleus of the lateral geniculate body and the medial geniculate body. Additionally, Met-enk-li cells were seen in every hypothalamic nucleus except in the supraoptic. Variable densities of labeled fibers were also seen in all these nuclei except in the medial geniculate body and in most areas of the lateral posterior and pulvinar nuclei. In the mesencephalon, positive cells were found in the periaqueductal gray, the Edinger-Westphal and interpeduncular nuclei, delimited areas of the superior and inferior colliculi and the ventral tegmental area. In the rhombencephalon, labeled cells were seen in the majority of the nuclei in the latero-dorsal pontine tegmentum, the nuclei of the lateral lemniscus, the trapezoid, vestibular medial, vestibular inferior and cochlear nuclei, the prepositus hypoglossal, the nucleus of the solitary tract and the dorsal motor nucleus of the vagus, the infratrigeminal nucleus and the caudal part of the spinal trigeminal nucleus and in the rhombencephalic reticular formation. The distribution of fibers included additionally the substantia nigra, all the trigeminal nerve nuclei, the facial nucleus and a restricted portion of the inferior olive. These results are discussed with regard to previous reports on the distribution of Met-enk in other species.
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Affiliation(s)
- R Pego-Reigosa
- Departamento de Anatomía, Facultad de Veterinaria, Universidad de Santiago, 27002, Lugo, Spain
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14
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Nicot A, Ogawa S, Berman Y, Carr KD, Pfaff DW. Effects of an intrahypothalamic injection of antisense oligonucleotides for preproenkephalin mRNA in female rats: evidence for opioid involvement in lordosis reflex. Brain Res 1997; 777:60-8. [PMID: 9449413 DOI: 10.1016/s0006-8993(97)00967-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previous studies in female rats have shown that estrogen increases preproenkephalin (PPE) mRNA levels in the ventrolateral part of the ventromedial nucleus of the hypothalamus (VMHVL), an area implicated in the modulation of sexual behavior. In order to assess the physiological role of hypothalamic opioid expression in lordosis reflex 16-mer oligodeoxynucleotide (ODN) directed towards the PPE mRNA were acutely microinjected above the VMH of estradiol-primed ovariectomized rats. Estradiol-induced lordosis behavior was observed in response to a stud male 2 days thereafter. Antisense (without or with 4 mismatches) ODN injections near the VMHVL resulted in a significant reduction in lordosis quotient compared to control (reverse sense) ODN treatment or to antisense ODN injections targeted anterior or posterior to the VMHVL. In contrast, locomotor activity of these animals in the open-field test was not affected by ODN treatments. Enkephalin immunoreactive levels were determined by radioimmunoassay in the preoptic area, a major terminal field of the VMHVL. Estradiol-induced enkephalin levels were greatly reduced in antisense-treated groups. Using the in situ hybridization technique, PPE mRNA levels in the VMHVL were also determined. A 1.5-2-fold increase in PPE mRNA levels was observed in estradiol-treated rats compared to ovariectomized rats as previously described. This increase in PPE mRNA levels was not affected by ODN treatment, suggesting that the reduction of enkephalin expression was mainly due to physical blockade of PPE mRNA translation and not to its degradation. Taken together, these data further support the behavioral role of PPE expressing VMHVL neurons. They also highlight the in vivo potency of acute administration of antisense phosphorothioate ODNs in blocking neuronal target gene expression.
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Affiliation(s)
- A Nicot
- Laboratory of Neurobiology and Behavior, The Rockefeller University, New York, NY 10021, USA
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