Oxytocin increases the density of high affinity alpha(2)-adrenoceptors within the hypothalamus, the amygdala and the nucleus of the solitary tract in ovariectomized rats.
ABSTRACT Oxytocin induces long-term changes in, for example, blood pressure, spontaneous motor activity and corticosterone levels in rats. Previous studies in male rats have suggested a role for alpha(2)-adrenoceptors within the central nervous system in these effects. The aim of the present study was to investigate if oxytocin treatment in female rats would influence alpha(2)-adrenoceptors within the hypothalamus, the amygdala and the nucleus of the solitary tract (NTS). For this purpose, female ovariectomized (OVX) rats were treated with oxytocin (1 mg/kg s.c.) or saline once a day for 10 days. Rats were decapitated 5 days after the last injection, and brains and plasma were collected. Quantitative receptor autoradiography for characterization of high affinity alpha(2)-adrenoceptor agonist binding and radioimmunoassay for corticosterone were performed. Oxytocin increased the B(max) values of the alpha(2)-adrenoceptor agonist [3H]UK14.304 binding sites significantly in all the analyzed areas (P<0.05). K(d) values were unchanged. Plasma levels of corticosterone were significantly decreased in the oxytocin-treated rats (P<0.05). These findings are in further support of an interaction between oxytocin receptors and alpha(2)-adrenoceptors and show that oxytocin treatment may increase alpha(2)-adrenoceptor recognition probably leading to an increase in alpha(2)-adrenoceptor signaling in several parts of the brain.
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ABSTRACT: Abstract The role of central oxytocin in the regulation of cardiovascular parameters under resting conditions and during acute stress was investigated in male normotensive Wistar-Kyoto (WKY; n=40) and spontaneously hypertensive (SHR; n=28) rats. In Experiment 1 mean arterial blood pressure (MABP) and heart rate (HR) were recorded in WKY and SHR rats at rest and after an air jet stressor during intracerebroventricular (ICV) infusions of vehicle, oxytocin or oxytocin receptor (OTR) antagonist. In Experiment 2 the effects of vehicle, oxytocin and OTR antagonist were determined in WKY rats after prior administration of a V1a vasopressin receptor (V1aR) antagonist. Resting MABP and HR were not affected by any of the ICV infusions either in WKY or in SHR rats. In control experiments (vehicle), the pressor response to stress was significantly higher in SHR. Oxytocin enhanced the pressor response to stress in the WKY rats but reduced it in SHR. During V1aR blockade, oxytocin infusion entirely abolished the pressor response to stress in WKY rats. Combined blockade of V1aR and OTR elicited a significantly greater MABP response to stress than infusion of V1a antagonist and vehicle. This study reveals significant differences in the regulation of blood pressure in WKY and SHR rats during alarming stress. Specifically, the augmentation of the pressor response to stress by exogenous oxytocin in WKY rats is caused by its interaction with V1aR, and endogenous oxytocin regulates the magnitude of the pressor response to stress in WKY rats by simultaneous interaction with OTR and V1aR.Stress (Amsterdam, Netherlands) 12/2013; · 3.46 Impact Factor
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ABSTRACT: For dogs, humans are likely to be the most important feature in their environment influencing their welfare. To investigate a commonly occurring human–dog interaction, behavioural and endocrine responses of 12 female beagle dogs were measured before, upon and after the return of a familiar person. Each dog was left by the person in a test arena to which it had been habituated prior to the experiment. Three different treatments were applied when the person returned and each dog experienced all these in a balanced design; the familiar person entered the test arena and 1) initiated physical and verbal contact in a calm and friendly way (PV), 2) there was verbal contact only (V) or, as a ‘control’, 3) the person ignored the dog (C). Interaction continued for 4 min during which the person behaved in a standardized way according to the treatment. Blood samples were collected to investigate oxytocin and cortisol levels. Upon return, oxytocin increased initially, probably because of the dog seeing the person entering the room and walking towards the area where the dog was housed. In treatment PV, where physical contact was applied, elevated levels of oxytocin were observed even after the interaction had ended. Cortisol levels showed a decreasing curve throughout the test, however this decrease was most pronounced in treatment PV, possibly as a consequence of the oxytocin release. Also, dogs in this treatment initiated more physical contact with the familiar person and expressed more lip licking upon reunion. The initial responses to reunion in treatment V were tail wagging and vocalisations. When dogs were ignored upon reunion in treatment C, they could have redirected their approach-behaviour towards an assistant (who was always situated in the room). To conclude, the type of interaction evidently affected the endocrine and behavioural responses of dogs in different ways. The mere return of the familiar person had a positive effect on oxytocin levels and induced contact-seeking behaviour, whereas physical contact was necessary in order to induce a sustained increase in oxytocin levels and to decrease cortisol levels in the period following reunion.Physiology & Behavior 01/2014; 124:45–53. · 3.03 Impact Factor
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ABSTRACT: Drugs of abuse such as morphine or marijuana exert their effects through the activation of G-protein-coupled receptors (GPCRs), the opioid and cannabinoid receptors, respectively. Moreover, interactions between either of these receptors have been shown to be involved in the rewarding effects of drugs of abuse. Recent advances in the field, using a variety of approaches, have demonstrated that many GPCRs, including opioid, cannabinoid, and dopamine receptors, can form associations between different receptor subtypes or with other GPCRs to form heteromeric complexes. The formation of these complexes, in turn, leads to the modulation of the properties of individual protomers. The development of tools that can selectively disrupt GPCR heteromers as well as monoclonal antibodies that can selectively block signaling by specific heteromer pairs has indicated that heteromers involving opioid, cannabinoid, or dopamine receptors may play a role in various disease states. In this review, we describe evidence for opioid, cannabinoid, and dopamine receptor heteromerization and the potential role of GPCR heteromers in pathophysiological conditions.Progress in molecular biology and translational science 01/2013; 117:207-65. · 3.11 Impact Factor