RESUMO
Sexual activity causes differential changes in the expression of markers of neural activation (c-Fos and ΔFosB) and neural plasticity (Arc and BDNF/trkB), as determined either by Western Blot (BDNF, trkB, Arc, and ΔFosB) or immunohistochemistry (BDNF, trkB, Arc, and c-Fos), in the hippocampus of male Roman high (RHA) and low avoidance (RLA) rats, two psychogenetically selected rat lines that display marked differences in sexual behavior (RHA rats exhibit higher sexual motivation and better copulatory performance than RLA rats). Both methods showed (with some differences) that sexual activity modifies the expression levels of these markers in the hippocampus of Roman rats depending on: (i) the level of sexual experience, that is, changes were usually more evident in sexually naïve than in experienced rats; (ii) the hippocampal partition, that is, BDNF and Arc increased in the dorsal but tended to decrease in the ventral hippocampus; (iii) the marker considered, that is, in sexually experienced animals BDNF, c-Fos, and Arc levels were similar to those of controls, while ΔFosB levels increased; and (iv) the rat line, that is, changes were usually larger in RHA than RLA rats. These findings resemble those of early studies in RHA and RLA rats showing that sexual activity influences the expression of these markers in the nucleus accumbens, medial prefrontal cortex, and ventral tegmental area, and show for the first time that also in the hippocampus sexual activity induces neural activation and plasticity, events that occur mainly during the first phase of the acquisition of sexual experience and depend on the genotypic/phenotypic characteristics of the animals.
Assuntos
Fator Neurotrófico Derivado do Encéfalo , Hipocampo , Animais , Aprendizagem da Esquiva/fisiologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Proteínas do Citoesqueleto/metabolismo , Hipocampo/metabolismo , Masculino , Proteínas do Tecido Nervoso/metabolismo , Plasticidade Neuronal , Núcleo Accumbens , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Receptor trkB/metabolismoRESUMO
A continuously increasing amount of research shows that oxytocin is involved in numerous central functions. Among the functions in which oxytocin is thought to be involved are those that play a role in social and sexual behaviors, and the involvement of central oxytocin in erectile function and sexual behavior was indeed one of the first to be discovered in laboratory animals in the 1980s. The first part of this review summarizes the results of studies done in laboratory animals that support a facilitatory role of oxytocin in male and female sexual behavior and reveal mechanisms through which this ancient neuropeptide participates in concert with other neurotransmitters and neuropeptides in this complex function, which is fundamental for the species reproduction. The second part summarizes the results of studies done mainly with intranasal oxytocin in men and women with the aim to translate the results found in laboratory animals to humans. Unexpectedly, the results of these studies do not appear to confirm the facilitatory role of oxytocin found in male and female sexual behavior in animals, both in men and women. Possible explanations for the failure of oxytocin to improve sexual behavior in men and women and strategies to attempt to overcome this impasse are considered.
Assuntos
Disfunção Erétil/metabolismo , Ocitocina/metabolismo , Ereção Peniana , Comportamento Sexual , Animais , Feminino , Humanos , MasculinoRESUMO
Fipronil (FPN), a widely used pesticide for agricultural and non-agricultural pest control, is possibly neurotoxic for mammals. Brain monoaminergic systems, involved in virtually all brain functions, have been shown to be sensitive to numerous pesticides. Here, we addressed the hypothesis that chronic exposure to FPN could modify brain monoamine neurochemistry. FPN (10 mg/kg) was chronically administered for 21 days through oral gavage in rats. Thereafter, the tissue concentrations of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid; serotonin (5-HT) and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA); and noradrenaline (NA) were measured in 30 distinct brain regions. FPN significantly decreased DA and its metabolite levels in most striatal territories, including the nucleus accumbens and the substantia nigra (SN). FPN also diminished 5-HT levels in some striatal regions and the SN. The indirect index of the turnovers, DOPAC/DA and 5-HIAA/5-HT ratios, was increased in numerous brain regions. FPN reduced the NA content only in the nucleus accumbens core. Using the Bravais-Pearson test to study the neurochemical organization of monoamines through multiple correlative analyses across the brain, we found fewer correlations for NA, DOPAC/DA, and 5-HIAA/5-HT ratios, and an altered pattern of correlations within and between monoamine systems. We therefore conclude that the chronic administration of FPN in rats induces massive and inhomogeneous changes in the DA and 5-HT systems in the brain.
Assuntos
Monoaminas Biogênicas/metabolismo , Encéfalo/efeitos dos fármacos , Neuroquímica/métodos , Pirazóis/farmacologia , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Animais , Encéfalo/metabolismo , Dopamina , Ácido Homovanílico/metabolismo , Ácido Hidroxi-Indolacético/metabolismo , Inseticidas/farmacologia , Masculino , Norepinefrina/metabolismo , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Ratos Sprague-Dawley , Serotonina/metabolismo , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismoRESUMO
Oxytocin (5-100ng), but not Arg8-vasopressin (100ng), injected unilaterally into the bed nucleus of the stria terminalis (BNST) induces penile erection and yawning in a dose-dependent manner in male rats. The minimal effective dose was 20ng for penile erection and 5ng for yawning. Oxytocin responses were abolished not only by the oxytocin receptor antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin (1µg), but also by (+) MK-801 (1µg), an excitatory amino acid receptor antagonist of the N-methyl-d-aspartic acid (NMDA) subtype, SCH 23390 (1µg), a D1 receptor antagonist, but not haloperidol (1µg), a D2 receptor antagonist, and SMTC (40µg), an inhibitor of neuronal nitric oxide synthase, injected into the BNST 15min before oxytocin. Oxytocin-induced penile erection, but not yawning, was also abolished by CNQX (1µg), an excitatory amino acid receptor antagonist of the AMPA subtype. In contrast, oxytocin responses were not reduced by bicuculline (20ng), a GABAA receptor antagonist, phaclofen (5µg), a GABAB receptor antagonist, CP 376395, a CRF receptor-1 antagonist (5µg), or astressin 2B, a CRF receptor-2 antagonist (150ng). Considering the ability of NMDA (100ng) to induce penile erection and yawning when injected into the BNST and the available evidence showing possible interaction among oxytocin, glutamic acid, and dopamine in the BNST, oxytocin possibly activates glutamatergic neurotransmission in the BNST. This in turn leads to the activation of neural pathways projecting back to the paraventricular nucleus, medial preoptic area, ventral tegmental area, and/or ventral subiculum/amygdala, thereby inducing penile erection and yawning.
Assuntos
Ocitocina/administração & dosagem , Ereção Peniana/efeitos dos fármacos , Núcleos Septais/efeitos dos fármacos , Bocejo/efeitos dos fármacos , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/metabolismo , Animais , Dopamina/metabolismo , Dopamina/fisiologia , Ácido Glutâmico/metabolismo , Ácido Glutâmico/fisiologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Infusões Intraventriculares , Masculino , Óxido Nítrico/metabolismo , Óxido Nítrico/fisiologia , Ocitocina/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Ocitocina/metabolismo , Núcleos Septais/metabolismo , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/metabolismoRESUMO
Oxytocin is involved in the control of different behaviors, from sexual behavior and food consumption to empathy, social and affective behaviors. An imbalance of central oxytocinergic neurotransmission has been also associated with different mental pathologies, from depression, anxiety and anorexia/bulimia to schizophrenia, autism and drug dependence. This study shows that oxytocin may also play a role in the control of locomotor activity. Accordingly, intraperitoneal oxytocin (0.5-2000µg/kg) reduced locomotor activity of adult male rats. This effect was abolished by d(CH2)5Tyr(Me)(2)-Orn(8)-vasotocin, an oxytocin receptor antagonist, given into the lateral ventricles at the dose of 2µg/rat, which was ineffective on locomotor activity. Oxytocin (50-200ng/site) also reduced and d(CH2)5Tyr(Me)(2)-Orn(8)-vasotocin (2µg/site) increased locomotor activity when injected bilaterally into the substantia nigra, a key area in the control of locomotor activity. Conversely, the destruction of nigral neurons bearing oxytocin receptors by the recently characterized neurotoxin oxytocin-saporin injected into the substantia nigra, increased basal locomotor activity. Since oxytocin-saporin injected into the substantia nigra caused a marked reduction of neurons immunoreactive for tyrosine hydroxylase (e.g., nigrostriatal dopaminergic neurons) and for vesicular glutamate transporters VGluT1, VGluT2 and VGluT3 (e.g., glutamatergic neurons), but not for glutamic acid decarboxylase (e.g., GABAergic neurons), together these findings suggest that oxytocin influences locomotor activity by acting on receptors localized presynaptically in nigral glutamatergic nerve terminals (which control the activity of nigral GABAergic efferent neurons projecting to brain stem nuclei controlling locomotor activity), rather than on receptors localized in the cell bodies/dendrites of nigrostriatal dopaminergic neurons.
Assuntos
Locomoção/efeitos dos fármacos , Ocitocina/metabolismo , Ocitocina/farmacologia , Substância Negra/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Dendritos/metabolismo , Dendritos/fisiologia , Dopamina/fisiologia , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/fisiologia , Imuno-Histoquímica , Masculino , Neurônios/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de Ocitocina/metabolismo , Receptores de Ocitocina/fisiologia , Substância Negra/patologiaRESUMO
BACKGROUND: Dopamine is reduced in the brain of rats treated with fipronil, a broad-spectrum insecticide. VGF (no acronym) is a neurotrophin-inducible protein expressed as the 75â¯kDa form (precursor or pro-VGF) or its truncated peptides. VGF immunostaining has been revealed using an antibody against the C-terminal nonapeptide of the rat pro-VGF in the nerve terminals of the rat substantia nigra, where it was reduced after 6-hydroxydopamine treatment. It is unknown whether pro-VGF and/or its shortened peptides are present in these neurons. Therefore, the aim of this study was first to determine which types of VGF are expressed in the normal substantia nigra (and striatum) and then to determine VGF modulations and whether they occur in parallel with locomotor changes after fipronil injection. METHODS: Rats were divided into two groups that received a unilateral intranigral infusion of either fipronil (25⯵g) diluted in dimethyl sulfoxide (DMSO) or DMSO alone, and then were tested for locomotor activity. An untreated group of rats (n=4) was used for identification of the VGF fragments using high performance liquid chromatography-mass spectrometry and western blot, while changes in treated groups (fipronil vs DMSO, each n=6) were investigated by immunohistochemistry using an antibody against the rat pro-VGF C-terminal nonapeptide in parallel with the anti-tyrosine hydroxylase antibody. RESULTS: In untreated rats, the VGF C-terminal antibody identified mostly a 75â¯kDa band in the substantia nigra and striatum, supporting the finding of high-resolution mass spectrometry, which revealed fragments covering the majority of the pro-VGF sequence. Furthermore, several shortened VGF C-terminal forms (varying from 10 to 55â¯kDa) were also found by western blot, while high-resolution mass spectrometry revealed a C-terminal peptide overlapping the immunogen used to create the VGF antibody in both substantia nigra and striatum. In the substantia nigra of fipronil-treated rats, immunostaining for tyrosine hydroxylase and VGF was reduced compared to DMSO-treated rat group, and this was related with significant changes in locomotor activity. CONCLUSION: Fipronil has the ability to modulate the production of pro-VGF and/or its C-terminal truncated peptides in the nigrostriatal system indicating its intimate interaction with the dopaminergic neurotransmission and implying a potential function in modulating locomotor activity.
Assuntos
Dopamina , Praguicidas , Pirazóis , Ratos , Masculino , Animais , Dopamina/metabolismo , Ratos Sprague-Dawley , Praguicidas/metabolismo , Dimetil Sulfóxido/metabolismo , Corpo Estriado/metabolismo , Fatores de Crescimento Neural/metabolismoRESUMO
Erectile dysfunction (ED) is the inability to get and maintain an adequate penile erection for satisfactory sexual intercourse. Due to its negative impacts on men's life quality and increase during aging (40% of men between 40 and 70 years), ED has always attracted researchers of different disciplines, from urology, andrology and neuropharmacology to regenerative medicine, and vascular and prosthesis implant surgery. Locally and/or centrally acting drugs are used to treat ED, e.g., phosphodiesterase 5 inhibitors (first in the list) given orally, and phentolamine, prostaglandin E1 and papaverine injected intracavernously. Preclinical data also show that dopamine D4 receptor agonists, oxytocin and α-MSH analogues may have a role in ED treatment. However, since pro-erectile drugs are given on demand and are not always efficacious, new strategies are being tested for long lasting cures of ED. These include regenerative therapies, e.g., stem cells, plasma-enriched platelets and extracorporeal shock wave treatments to cure damaged erectile tissues. Although fascinating, these therapies are laborious, expensive and not easily reproducible. This leaves old vacuum erection devices and penile prostheses as the only way to get an artificial erection and sexual intercourse with intractable ED, with penile prosthesis used only by accurately selected patients.
RESUMO
Oxytocin (80 ng) induces yawning when injected into the caudal part of the ventral tegmental area, the hippocampal ventral subiculum and the posteromedial nucleus of the amygdala of male rats. The behavioural response occurred concomitantly with an increase in the concentration of extracellular dopamine and its main metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the dialysate obtained from the shell of the nucleus accumbens and of the prelimbic medial prefrontal cortex by means of intracerebral microdialysis. Both oxytocin responses were significantly reduced by d(CH2)5Tyr(Me)²-Orn8-vasotocin, a selective oxytocin receptor antagonist, injected in the above brain areas 15 min before oxytocin. Similar results were obtained by activating central oxytocinergic neurons originating in the paraventricular nucleus of the hypothalamus and projecting to the ventral tegmental area, the hippocampus and the amygdala, with the dopamine agonist apomorphine given at a dose that induces yawning when injected into the paraventricular nucleus. Since oxytocin is considered a key regulator of emotional and social reward that enhances amygdala-dependent, socially reinforced learning and emotional empathy, mesolimbic and mesocortical dopamine neurons play a key role in motivation and reward, and yawning in mammals is considered a primitive, unconscious form of empathy, the present results support the hypothesis that oxytocinergic neurons originating in the paraventricular nucleus of the hypothalamus and projecting to the above brain areas and mesolimbic and mesocortical dopaminergic neurons participate in the complex neural circuits that play a role in the above mentioned functions.
Assuntos
Encéfalo/efeitos dos fármacos , Comunicação Celular/efeitos dos fármacos , Neurônios Dopaminérgicos/efeitos dos fármacos , Ocitocina/farmacologia , Bocejo/efeitos dos fármacos , Ácido 3,4-Di-Hidroxifenilacético/farmacologia , Animais , Encéfalo/citologia , Encéfalo/fisiologia , Mapeamento Encefálico , Comunicação Celular/fisiologia , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/fisiologia , Agonistas de Dopamina/farmacologia , Neurônios Dopaminérgicos/fisiologia , Hipotálamo/citologia , Hipotálamo/efeitos dos fármacos , Hipotálamo/fisiologia , Sistema Límbico/citologia , Sistema Límbico/efeitos dos fármacos , Sistema Límbico/fisiologia , Masculino , Modelos Biológicos , Ratos , Ratos Sprague-Dawley , Fatores Sexuais , Bocejo/fisiologiaRESUMO
Based on the dopamine D(4) receptor partial agonist FAUC 3019, a series of azulenylmethylpiperazines was synthesized and affinities for the monoaminergic GPCRs including dopamine, serotonin, histamine and α-adrenergic receptor subtypes were determined. Ligand efficacies of the most promising test compounds revealed the N,N-dimethylaminomethyl substituted azulene 11 to be the most potent D(4) partial agonist (EC(50)=0.41 nM). This candidate was investigated for its ability to promote penile erection. Applying an in vivo animal model, test compound 11 turned out to stimulate penile erection in male rats with superior potency in low concentrations when compared to apomorphine.
Assuntos
Azulenos/química , Azulenos/uso terapêutico , Disfunção Erétil/tratamento farmacológico , Metilaminas/uso terapêutico , Animais , Azulenos/síntese química , Humanos , Cinética , Masculino , Metilaminas/síntese química , Metilaminas/química , Ratos , Receptores Dopaminérgicos/química , Receptores Dopaminérgicos/metabolismo , Receptores de Dopamina D4/agonistas , Receptores de Dopamina D4/metabolismo , Receptores Histamínicos/química , Receptores Histamínicos/metabolismo , SuínosRESUMO
Early and recent studies show that dopamine through its neuronal systems and receptor subtypes plays different roles in the control of male sexual behavior. These studies show that (i) the mesolimbic/mesocortical dopaminergic system plays a key role in the preparatory phase of sexual behavior, e.g., in sexual arousal, motivation and reward, whereas the nigrostriatal system controls the sensory-motor coordination necessary for copulation, (ii) the incertohypothalamic system is involved in the consummatory aspects of sexual behavior (penile erection and copulation), but evidence for its role in sexual motivation is also available, (iii) the pro-sexual effects of dopamine occur in concert with neural systems interconnecting the hypothalamus and preoptic area with the spinal cord, ventral tegmental area and other limbic brain areas and (iv) D2 and D4 receptors play a major role in the pro-sexual effects of dopamine. Despite some controversy, increases or decreases, respectively, of brain dopamine activity induced by drugs or that occur physiologically, usually improves or worsens, respectively, sexual activity. These findings suggest that an altered central dopaminergic tone plays a role in mental pathologies characterized by aberrant sexual behavior, and that pro-erectile D4 receptor agonists may be considered a new strategy for the treatment of erectile dysfunction in men.
RESUMO
Nitric oxide (NO), the neuromodulator/neurotransmitter formed from l-arginine by neuronal, endothelial and inducible NO synthases, is involved in numerous functions across the body, from the control of arterial blood pressure to penile erection, and at central level from energy homeostasis regulation to memory, learning and sexual behavior. The aim of this work is to review earlier studies showing that NO plays a role in erectile function and sexual behavior in the hypothalamus and its paraventricular nucleus and the medial preoptic area, and integrate these findings with those of recent studies on this matter. This revisitation shows that NO influences erectile function and sexual behavior in males and females by acting not only in the paraventricular nucleus and medial preoptic area but also in extrahypothalamic brain areas, often with different mechanisms. Most importantly, since these areas are strictly interconnected with the paraventricular nucleus and medial preoptic area, send to and receive neural projections from the spinal cord, in which sexual communication between brain and genital apparatus takes place, this review reveals that central NO participates in concert with neurotransmitters/neuropeptides to a neural circuit controlling both the consummatory (penile erection, copulation, lordosis) and appetitive components (sexual motivation, arousal, reward) of sexual behavior.
Assuntos
Sistema Nervoso Central/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico/metabolismo , Comportamento Sexual/fisiologia , Animais , Arginina/metabolismo , Feminino , Humanos , Masculino , Ereção PenianaRESUMO
Saporin conjugated to oxytocin (OXY-SAP) destroys neurons expressing oxytocinergic receptors. When injected unilaterally in the substantia nigra of male rats, OXY-SAP causes a dose-dependent decrease up to 55 % in nigral Tyrosine Hydroxylase (TH)-immunoreactivity compared to control mock peptide BLANK-SAP- and PBS-treated rats or the contralateral substantia nigra. TH decrease was parallel to a dopamine content decrease in the ipsilateral striatum compared to BLANK-SAP- or PBS-treated rats or the contralateral striatum. OXY-SAP-treated rats showed a small but significant increase of locomotor activity 28 days after intranigral injection in the Open field test compared to BLANK-SAP- or PBS-treated rats, in line with an inhibitory role of nigral oxytocin on locomotor activity. OXY-SAP-, but not BLANK-SAP- or PBS-treated rats, also showed marked dose-dependent rotational turning ipsilateral to the injected substantia nigra when challenged with d-amphetamine, but not with apomorphine. Under isoflurane anesthesia OXY-SAP-treated rats showed levels of extracellular dopamine in the dialysate from the ipsilateral striatum only half those of BLANK-SAP- or PBS-treated rats or the contralateral striatum. When treated with d-amphetamine, OXY-SAP_60/120 rats showed increased extracellular dopamine levels in the dialysate from the ipsilateral striatum two third/one third only of those found in BLANK-SAP- or PBS-treated rats or the contralateral striatum, respectively. These results show that OXY-SAP destroys nigrostriatal dopaminergic neurons expressing oxytocin receptors leading to a reduced striatal dopamine function.
Assuntos
Corpo Estriado/efeitos dos fármacos , Neurônios Dopaminérgicos/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Ocitocina/análogos & derivados , Saporinas/farmacologia , Substância Negra/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Corpo Estriado/metabolismo , Dopamina/metabolismo , Neurônios Dopaminérgicos/metabolismo , Masculino , Vias Neurais/efeitos dos fármacos , Vias Neurais/metabolismo , Ocitocina/farmacologia , Ratos , Comportamento Estereotipado/efeitos dos fármacos , Substância Negra/metabolismoRESUMO
INTRODUCTION: Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions. AIM: To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function. METHODS: State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period. MAIN OUTCOME MEASURES: Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate. RESULTS: Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine. CONCLUSIONS: Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.
Assuntos
Disfunções Sexuais Fisiológicas/fisiopatologia , Animais , Encéfalo/fisiopatologia , Sistema Nervoso Central/efeitos dos fármacos , Sistema Nervoso Central/fisiopatologia , Ejaculação/efeitos dos fármacos , Ejaculação/fisiologia , Disfunção Erétil/tratamento farmacológico , Disfunção Erétil/etiologia , Disfunção Erétil/fisiopatologia , Feminino , Terapia Genética , Humanos , Libido/efeitos dos fármacos , Libido/fisiologia , Imageamento por Ressonância Magnética , Masculino , Ereção Peniana/efeitos dos fármacos , Ereção Peniana/fisiologia , Medicina Regenerativa , Disfunções Sexuais Fisiológicas/tratamento farmacológico , Disfunções Sexuais Fisiológicas/etiologiaRESUMO
Experimental evidence shows that the phenylpyrazole pesticide fipronil exerts neurotoxic effects at central level in rodents, and in particular on nigrostriatal dopaminergic neurons, whose degeneration is well known to cause motor and non-motor deficits in animals and in humans. In order to characterize better the central neurotoxic effect of fipronil, we injected fipronil (15 and 25 µg) dissolved in dimethyl sulfoxide (DMSO) unilaterally into the substantia nigra of male rats. Male rats injected with DMSO unilaterally into the substantia nigra were used as controls. Control and fipronil-treated rats were then tested in different motor (i.e., open field arena, rotarod, tail flick) and non motor tests (novel object recognition, social interaction) 15 days after injection. A systemic challenge dose of the dopamine-agonist apomorphine was also used to study the presence of a rotational behavior. Sixteen days after fipronil or DMSO injection into the substantia nigra, rats were sacrificed, and either striatal dopamine content or substantia nigra tyrosine hydroxylase (TH) immunoreactivity were measured. The results confirm that the unilateral injection of fipronil into the substantia nigra caused the degeneration of nigrostriatal dopaminergic neurons, which leads to a decrease around 50 % in striatal dopamine content and substantia nigra TH imunoreactivity. This occurred together with changes in motor activity and coordination, and in nociception but not in recognition memory and in social interaction, as revealed by the results of the behavioral experiments performed in fipronil-treated rats compared to vehicle-treated rats 15 days after treatment, as found with other compounds that destroy nigrostriatal dopaminergic neurons.
Assuntos
Corpo Estriado/efeitos dos fármacos , Dopamina/metabolismo , Inseticidas/toxicidade , Atividade Motora/efeitos dos fármacos , Nociceptividade/efeitos dos fármacos , Pirazóis/toxicidade , Substância Negra/efeitos dos fármacos , Tirosina 3-Mono-Oxigenase/efeitos dos fármacos , Animais , Apomorfina/farmacologia , Corpo Estriado/metabolismo , Agonistas de Dopamina/farmacologia , Imuno-Histoquímica , Locomoção/efeitos dos fármacos , Masculino , Teste de Campo Aberto , Ratos , Reconhecimento Psicológico/efeitos dos fármacos , Teste de Desempenho do Rota-Rod , Interação Social/efeitos dos fármacos , Substância Negra/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Central dopamine plays a key role in sexual behavior. Recently, a Dopamine Transporter knockout (DAT KO) rat has been developed, which displays several behavioral dysfunctions that have been related to increased extracellular dopamine levels and altered dopamine turnover secondary to DAT gene silencing. This prompted us to characterize the sexual behavior of these DAT KO rats and their heterozygote (HET) and wild type (WT) counterparts in classical copulatory tests with a sexually receptive female rat and to verify if and how the acquisition of sexual experience changes along five copulatory tests in these rat lines. Extracellular dopamine and glutamic acid concentrations were also measured in the dialysate obtained by intracerebral microdialysis from the nucleus accumbens (Acb) shell of DAT KO, HET and WT rats, which underwent five copulatory tests, when put in the presence of an inaccessible sexually receptive female rat and when copulation was allowed. Markers of neurotropism (BDNF, trkB), neural activation (Δ-FosB), functional (Arc and PSA-NCAM) and structural synaptic plasticity (synaptophysin, syntaxin-3, PSD-95) were also measured in the ventral tegmental area (VTA), Acb (shell and core) and medial prefrontal cortex (mPFC) by Western Blot assays. The results indicate that the sexual behavior of DAT KO vs. HET and WT rats shows peculiar differences, mainly due to a more rapid acquisition of stable sexual activity levels and to higher levels of sexual motivation and activity. These differences occurred with differential changes in dopamine and glutamic acid concentrations in Acb dialysates during sexual behavior, with lower increases of dopamine and glutamic acid in DAT KO vs. WT and HET rats, and a lower expression of the markers investigated, mainly in the mPFC, in DAT KO vs. WT rats. Together these findings confirm a key role of dopamine in sexual behavior and provide evidence that the permanently high levels of dopamine triggered by DAT gene silencing cause alterations in both the frontocortical glutamatergic neurons projecting to the Acb and VTA and in the mesolimbic dopaminergic neurons, leading to specific brain regional changes in trophic support and neuroplastic processes, which may have a role in the sexual behavior differences found among the three rat genotypes.
RESUMO
Oxytocin (20-100 ng) was found to be able to induce penile erection when injected unilaterally into the ventral subiculum or the posteromedial cortical nucleus of the amygdala of male rats. The pro-erectile effect started mostly 30 min after treatment and was abolished by the prior injection of d(CH(2))(5)Tyr(Me)(2)-Orn(8)-vasotocin (1-2 microg), an oxytocin receptor antagonist, into the ventral subiculum or posteromedial cortical nucleus. Oxytocin-induced penile erection occurred 15 min after the increase in the concentration of extracellular dopamine and its metabolite 3,4-dihydroxyphenylacetic acid in the dialysate obtained from the nucleus accumbens, which was also abolished by d(CH(2))(5)Tyr(Me)(2)-Orn(8)-vasotocin. The pro-erectile effect of oxytocin was also reduced by cis-flupentixol (2 and 5 microg), a dopamine receptor antagonist, injected into the nucleus accumbens, and by (+)MK-801 (5 microg), a noncompetitive N-methyl-d-aspartate receptor antagonist, injected into the ventral tegmental area, but not into the nucleus accumbens. Together with studies showing that glutamatergic efferents from the ventral subiculum/posteromedial cortical nucleus of the amygdala to other areas of the limbic system modulate the activity of mesolimbic dopaminergic neurons, these findings suggest that oxytocin injected into these areas increases glutamatergic neurotransmission in the ventral tegmental area. This, in turn, activates mesolimbic dopaminergic neurons, leading to penile erection. These results provide evidence that the ventral subiculum and the posteromedial cortical nucleus of the amygdala participate in a neural circuit that controls not only the consummatory aspects of sexual behaviour (e.g. penile erection and copulatory performance), but also its motivational/reward aspects, confirming a key role of oxytocin and dopamine in these processes.
Assuntos
Tonsila do Cerebelo/fisiologia , Dopamina/metabolismo , Hipocampo/fisiologia , Núcleo Accumbens/fisiologia , Ocitocina/metabolismo , Ereção Peniana/fisiologia , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Tonsila do Cerebelo/efeitos dos fármacos , Animais , Espaço Extracelular/efeitos dos fármacos , Espaço Extracelular/metabolismo , Lateralidade Funcional , Ácido Glutâmico/metabolismo , Hipocampo/efeitos dos fármacos , Masculino , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Núcleo Accumbens/efeitos dos fármacos , Ereção Peniana/efeitos dos fármacos , Pênis/efeitos dos fármacos , Pênis/fisiologia , Ratos , Ratos Sprague-Dawley , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/fisiologiaRESUMO
INTRODUCTION: Orally active phosphodiesterase type 5 inhibitors (PDE5i), used in the treatment of erectile dysfunction, facilitate the relaxation of cavernous smooth muscle tissues by reducing the degradation of cyclic guanosine monophosphate. AIMS: The aims of this article were to determine whether PDE5i facilitate penile erection and male sexual behavior by acting also on the central nervous system and to investigate their mechanism of action at central level. METHODS: PDE5i (sildenafil, vardenafil, and tadalafil) given intraperitoneally (i.p.) (5 mg/kg and 10 mg/kg), intracerebroventricularly (i.c.v.) (10 microg and 50 microg), or into the ventral tegmental area (VTA) (10 microg) were tested in the noncontact erection test in male Sprague-Dawley rats screened for their ability to display or not display this sexual response. Extracellular dopamine was measured in the dialysate obtained from the nucleus accumbens by intracerebral microdialysis on injection of PDE5i into the VTA. MAIN OUTCOME MEASURES. Noncontact erections were counted after intraperitoneal, intracerebroventricular, or intra-VTA treatment with PDE5i. Extracellular dopamine was measured in the dialysate from the nucleus accumbens when sildenafil or vardenafil was given into the VTA. Results. PDE5i induced a significant increase of noncontact erections in male rats displaying this sexual response following intraperitoneal or intracerebroventricular administration at the highest dose tested. However, both doses significantly increased noncontact erections in male rats not displaying this sexual response. Similar results were found when PDE5i were injected into the caudal VTA. Noncontact erections increased concomitantly to a rise in extracellular dopamine in the dialysate from the nucleus accumbens. CONCLUSIONS: The results suggest that PDE5i may increase sexual arousal by acting in the central nervous system. This effect may be mediated (at least in part) by the activation of mesolimbic dopaminergic neurons.
Assuntos
Encéfalo/efeitos dos fármacos , Ereção Peniana/efeitos dos fármacos , Inibidores da Fosfodiesterase 5 , Inibidores de Fosfodiesterase/farmacologia , Análise de Variância , Animais , Área Sob a Curva , Nível de Alerta/efeitos dos fármacos , Encéfalo/fisiologia , Carbolinas/farmacologia , GMP Cíclico , Dopamina/análise , Dopamina/metabolismo , Feminino , Imidazóis/farmacologia , Masculino , Microdiálise , Músculo Liso/efeitos dos fármacos , Músculo Liso/fisiologia , Óxido Nítrico , Núcleo Accumbens/química , Ereção Peniana/fisiologia , Piperazinas/farmacologia , Purinas/farmacologia , Ratos , Ratos Sprague-Dawley , Citrato de Sildenafila , Sulfonas/farmacologia , Tadalafila , Triazinas/farmacologia , Dicloridrato de Vardenafila , Área Tegmentar Ventral/efeitos dos fármacosRESUMO
Sexual behavior plays a fundamental role for reproduction in mammals and other animal species. It is characterized by an anticipatory and a consummatory phase, and several copulatory parameters have been identified in each phase, mainly in rats. Sexual behavior varies significantly across rats even when they are of the same strain and reared under identical conditions. This review shows that rats of the same strain selectively bred for showing a divergent behavioral trait when exposed to stress or novelty (i.e. Roman high and low avoidance rats, bred for their different avoidance response to the shuttle box, and high and low novelty exploration responders rats, bred for their different exploratory response to a novel environment) or a spontaneous behavior with divergent frequency (i.e. low and high yawning frequency rats, bred for their divergent yawning frequency) show similar differences in sexual behavior, mainly in copulatory pattern, but also in sexual motivation. As shown by behavioral pharmacology and intracerebral microdialysis experiments carried out mainly in Roman rats, these sexual differences may be due to a more robust dopaminergic tone present in the mesocorticolimbic dopaminergic system of one of the two sub-lines (e.g. high avoidance, high novelty exploration, and low yawning rat sub-lines). Thus, differences in genotype and/or in prenatal/postnatal environment lead not only to individual differences in temperament and environmental/emotional reactivity but also in sexual behavior. Because of the highly conserved mechanisms controlling reproduction in mammals, this may occur not only in rats but also in humans.
Assuntos
Dopamina/metabolismo , Comportamento Sexual/fisiologia , Estresse Fisiológico/fisiologia , Bocejo/fisiologia , Animais , Aprendizagem da Esquiva/fisiologia , Motivação/fisiologia , RatosRESUMO
Oxytocin (5, 20 and 100â¯ng) injected unilaterally into the bed nucleus of the stria terminalis (BNST) of male rats stereotaxically implanted with a microinjection cannula coupled to a microdialysis probe, induces penile erection and yawning that occur concomitantly with a dose-dependent increase in the extracellular concentration of glutamic acid, dopamine and its main metabolite 3,4-dihydroxyphenilacetic acid (DOPAC), and nitrites (NO2-) in the dialysate obtained from the BNST by intracerebral microdialysis. The responses induced by oxytocin (100â¯ng) were all abolished by the oxytocin receptor antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin (1⯵g), and reduced by CNQX (1⯵g), a competitive antagonist of the AMPA receptors, both given into the BNST 25â¯min before oxytocin. In contrast, (+) MK-801 (1⯵g), a non-competitive antagonist of NMDA receptors, and SCH 23390 (1⯵g), a selective dopamine D1 receptor antagonist, reduced penile erection and yawning, but not glutamic acid and dopamine increases in the BNST dialysate induced by oxytocin. Immunohistochemistry revealed oxytocin-labelled neuronal structures in close proximity to tyrosine hydroxylase-labelled neurons or nitric oxide synthase-labelled cell bodies surrounded by intense vesicular glutamate transporter1-stained synapses in BNST sections where oxytocin injections induce the above responses. Together, these findings show that oxytocin injected into the BNST induces penile erection and yawning by activating not only the glutamatergic (and nitrergic) but also the dopaminergic neurotransmission, leading in turn to the activation of neural pathways mediating penile erection and yawning.
Assuntos
Ocitocina/farmacologia , Ereção Peniana/efeitos dos fármacos , Bocejo/efeitos dos fármacos , Animais , Dopamina/metabolismo , Antagonistas de Dopamina/farmacologia , Ácido Glutâmico/metabolismo , Imuno-Histoquímica/métodos , Masculino , Microdiálise/métodos , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/metabolismo , Ocitocina/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Ocitocina/metabolismo , Núcleos Septais/efeitos dos fármacos , Núcleos Septais/fisiologiaRESUMO
Male Roman High- (RHA) and Low-Avoidance (RLA) rats display significant differences in sexual behavior (RHA rats exhibit higher sexual motivation and better copulatory performance than RLA rats). These differences are very evident in sexually naïve rats (which copulate with a receptive female rat for the first time), and are still present, although reduced, after five copulatory tests, when sexual experience has been acquired. Since sexual activity is a natural reward that induces neural activation and synaptic plastic changes in limbic brain areas, we studied whether the differences in sexual activity between these rat lines are accompanied by changes in the expression of markers of neural activation and plasticity, i.e., c-Fos, ΔFosB (a truncated form of FosB), Brain-Derived Neurotrophic Factor (BDNF) and its tyrosine kinase receptor B (trkB) and Activity regulated cytoskeleton-associated (Arc) protein in the ventral tegmental area (VTA), nucleus accumbens (Acb) (core and shell) and medial prefrontal cortex (mPFC) of sexually naïve and experienced RHA and RLA rats by Western Blot and/or immunohistochemistry. This study shows that these markers changed differentially in the VTA, Acb and mPFC of RHA and RLA rats, after sexual activity. In both rat lines, the changes were very evident in naïve rats, tended to disappear in experienced rats and were higher in RHA than RLA rats. These findings confirm that sexual activity induces neural activation in limbic brain areas involved in motivation and reward, leading to changes in synaptic plasticity with sexual experience acquisition, and show that these depend on the animals' genotypic/phenotypic characteristics.