Effects of exogenous oxytocin and atosiban antagonist on GABA in different region of brain

Oxytocin receptors mediate oxytocin potentiation of methylphenidate-induced stimulation of accumbens dopamine in rats

While the illicit use and misuse of stimulants like cocaine and methylphenidate (MP) has increased, there remains no FDA-approved treatments for psychostimulant use disorders (PSUD). Oxytocin (OT) has shown promise as a potential pharmacotherapy for PSUD. Dopamine (DA) neurotransmission plays a significant role in PSUD. We have recently shown that OT blunts the reinforcing effects of MP but, surprisingly, enhanced MP-induced stimulation of DA levels. Such effects have been suggested as a result of activation of OT receptors or, alternatively, could be mediated by direct actions of OT on MP blockade of the DA transporter. Here, we employed fast scan cyclic voltammetry (FSCV) to investigate the effects of systemic OT on MP-induced changes in the dynamics of DA, phasic release and uptake, in the nucleus accumbens shell (NAS) of Sprague-Dawley rats. We also tested the systemic effects of an antagonist of OT receptors, atosiban, to counteract the OT enhancement of dopaminergic effects of MP under microdialysis procedures in the NAS in rats. Administration of OT alone (2 mg/kg; i.p.) did not significantly modify evoked NAS DA dynamics measured by FSCV, and when administered 10 min before MP (0.1, 0.3, 1.0 mg/kg; i.v.), OT did not potentiate MP-induced increases in phasic DA release and did not alter DA clearance rate, suggesting no direct interactions of OT with the MP-induced blockade of DA uptake. Also, OT alone did not elicit significant changes in tonic, extracellular NAS DA levels measured by microdialysis. However, consistent with previous studies, we observed that OT pretreatments (2 mg/kg; i.p.) potentiated MP-induced (0.1, 0.3, 1.0 mg/kg; i.v.) efflux of extracellular NAS DA levels. This effect was abolished when rats were pretreated with atosiban (2 mg/kg; i.p.), suggesting that OT receptors mediate this OT action. Overall, our results suggest that OT receptors mediated OT potentiation of MP-induced stimulation of extracellular NAS DA levels, likely driven by modulation of DA receptor signaling pathways, without affecting MP blockade of DAT.

Sex-specific and social experience-dependent oxytocin-endocannabinoid interactions in the nucleus accumbens: implications for social behaviour

Oxytocin modulates social behaviour across diverse vertebrate taxa, but the precise nature of its effects varies across species, individuals and lifetimes. Contributing to this variation is the fact that oxytocin's physiological effects are mediated through interaction with diverse neuromodulatory systems and can depend on the specifics of the local circuits it acts on. Furthermore, those effects can be influenced by both genetics and experience. Here we discuss this complexity through the lens of a specific neuromodulatory system, endocannabinoids, interacting with oxytocin in the nucleus accumbens to modulate prosocial behaviours in prairie voles. We provide a survey of current knowledge of oxytocin-endocannabinoid interactions in relation to social behaviour. We review in detail recent research in monogamous female prairie voles demonstrating that social experience, such as mating and pair bonding, can change how oxytocin modulates nucleus accumbens glutamatergic signalling through the recruitment of endocannabinoids to modulate prosocial behaviour toward the partner. We then discuss potential sex differences in experience-dependent modulation of the nucleus accumbens by oxytocin in voles based on new data in males. Finally, we propose that future oxytocin-based precision medicine therapies should consider how prior social experience interacts with sex and genetics to influence oxytocin actions. This article is part of the theme issue 'Interplays between oxytocin and other neuromodulators in shaping complex social behaviours'.

Effects of oxytocin and antagonist antidote atosiban on body weight and food intake of female mice, Mus musculus

Growing evidence suggests that oxytocin (OT) plays an important factor for the control of food intake, body weight, and energy metabolism in human and non-human animals. It has reported previously, the downregulation in oxytocin receptors (OTRs) expression is linked with the development of obesity, but exogenous OT reverse body weight and food intake in obese animal model. It is important to know that, whether intraperitoneal administration crosses blood brain barrier. Therefore, in the present experiment, we study the impact of intraperitoneal administration of synthetic OT 0.0116 mg/kg and antagonist atosiban (OTA) 1 mg/kg on food intake, and body weight of female mice, Mus musculus for different duration i.e. 30, 60, and 90 days. In this study, it was observed that there was significant decrease (p<0.001, one-way analysis of variance [ANOVA]) in the body weight (BW), food intake, and gonadosmatic indices (GSI) after the intraperitoneal exposure of OT at dose 0.0116 mg/kg up to 90 days and inhibits via antagonist atosiban. These results indicates that intraperitoneal administration of OT can be used for treatment for longer duration without any side effects and maintains homeostasis in physiologic system regulates body weight and gonadal weight in female mice, which represent an important therapeutic tool for the obesity and metabolic disorder in female.

A functional selective effect of oxytocin secreted under restraint stress in rats

Restraint stress (RS) is an unavoidable stress model that triggers activation of the autonomic nervous system, endocrine activity, and behavioral changes in rodents. Furthermore, RS induces secretion of oxytocin into the bloodstream, indicating a possible physiological role in the stress response in this model. The presence of oxytocin receptors in vessels and heart favors this possible idea. However, the role of oxytocin secreted in RS and effects on the cardiovascular system are still unclear. The aim of this study was to analyze the influence of oxytocin on cardiovascular effects during RS sessions. Rats were subjected to pharmacological (blockade of either oxytocin, vasopressin, or muscarinic receptors) or surgical (hypophysectomy or sinoaortic denervation) approaches to study the functional role of oxytocin and its receptor during RS. Plasma levels of oxytocin and vasopressin were measured after RS. RS increased arterial pressure, heart rate, and plasma oxytocin content, but not vasopressin. Treatment with atosiban (a Gi biased agonist) inhibited restraint-evoked tachycardia without affecting blood pressure. However, this effect was no longer observed after sinoaortic denervation, homatropine (M2 muscarinic antagonist) treatment or hypophysectomy, indicating that parasympathetic activation mediated by oxytocin secreted to the periphery is responsible for blocking the increase in tachycardic responses observed in the atosiban-treated group. Corroborating this, L-368,899 (oxytocin antagonist) treatment showed an opposite effect to atosiban, increasing tachycardic responses to restraint. Thus, this provides evidence that oxytocin secreted to the periphery attenuates tachycardic responses evoked by restraint via increased parasympathetic activity, promoting cardioprotection by reducing the stress-evoked heart rate increase.

Daily intake of Lactobacillus alleviates autistic-like behaviors by ameliorating the 5-hydroxytryptamine metabolic disorder in VPA-treated rats during weaning and sexual maturation

Probiotic therapy targeting gut-brain axis has been proven to be effective in treating autistic patients. The present study aimed to assess the ability of three Lactobacillus strains (L. helveticus CCFM1076, L. acidophilus La28, and L. acidophilus JCM 1132) to alleviate autistic-like behavioral symptoms in VPA-treated rats from weaning to sexual maturation. For the first time, we assessed the synthesis of 5-hydroxytryptamine (5HT) and the metabolic capacity of the 5HT system in the peripheral and central nervous systems (PNS and CNS, respectively) based on tryptophan metabolism based on VPA-induced autism model. We also assessed gut microbiota, and short-chain fatty acids (SCFAs) at the end of week 8. While improving autistic-like behavioral symptoms, we found L. helveticus CCFM1076 was more beneficial in regulating 5HT anabolism and catabolism, balancing excitatory and inhibitory neurotransmitter release in the PNS and CNS, and increasing oxytocin (OT) synthesis in the hypothalamus. A significant correlation was noted between 5HT levels and the release of GABA, glutamate (Glu), and OT, suggesting that 5HT plays a vital role in the neuroendocrine network. Analyses of the gut microbiota and SCFA levels revealed greater Turicibacter abundance and lower butyric acid levels in VPA-treated rats, which have been reported to be associated with 5HT levels. L. helveticus CCFM1076 helped reduce Turicibacter abundance and up-regulate butyric acid levels, while L. acidophilus La28 and L. acidophilus JCM 1132 did not. L. helveticus CCFM1076 restored neurotransmitter homeostasis by improving the balance of the 5HT system in the PNS and CNS, thereby ameliorating autistic-like behaviors. This finding will help in the development of bioproducts for treating autism and in the establishment of a treatment model mimicking the intestinal environment of autistic patients.

The Rostral Agranular Insular Cortex, a New Site of Oxytocin to Induce Antinociception

The rostral agranular insular cortex (RAIC) is a relevant structure in nociception. Indeed, recruitment of GABAergic activity in RAIC promotes the disinhibition of the locus ceruleus, which in turn inhibits (by noradrenergic action) the peripheral nociceptive input at the spinal cord level. In this regard, at the cortical level, oxytocin can modulate the GABAergic transmission; consequently, an interaction modulating nociception could exist between oxytocin and GABA at RAIC. Here, we tested in male Wistar rats the effect of oxytocin microinjection into RAIC during an inflammatory (by subcutaneous peripheral injection of formalin) nociceptive input. Oxytocin microinjection produces a diminution of (1) flinches induced by formalin and (2) spontaneous firing of spinal wide dynamic range cells. The above antinociceptive effect was abolished by microinjection (at RAIC) of the following: (1) L-368899 (an oxytocin receptor [OTR] antagonist) or by (2) bicuculline (a preferent GABAA receptor blocker), suggesting a GABAergic activation induced by OTR. Since intrathecal injection of an α2A-adrenoceptor antagonist (BRL 44408) partially reversed the oxytocin effect, a descending noradrenergic antinociception is suggested. Further, injection of L-368899 per se induces a pronociceptive behavioral effect, suggesting a tonic endogenous oxytocin release during inflammatory nociceptive input. Accordingly, we found bilateral projections from the paraventricular nucleus of the hypothalamus (PVN) to RAIC. Some of the PVN-projecting cells are oxytocinergic and destinate GABAergic and OTR-expressing cells inside RAIC. Aside from the direct anatomic link between PVN and RAIC, our findings provide evidence about the role of oxytocinergic mechanisms modulating the pain process at the RAIC level.SIGNIFICANCE STATEMENT Oxytocin is a neuropeptide involved in several functions ranging from lactation to social attachment. Over the years, the role of this molecule in pain processing has emerged, showing that, at the spinal level, oxytocin blocks pain transmission. The present work suggests that oxytocin also modulates pain at the cortical insular level by favoring cortical GABAergic transmission and activating descending spinal noradrenergic mechanisms. Indeed, we show that the paraventricular hypothalamicnucleus sends direct oxytocinergic projections to the rostral agranular insular cortex on GABAergic and oxytocin receptor-expressing neurons. Together, our data support the notion that the oxytocinergic system could act as an orchestrator of pain modulation.

Methylation in Syn and Psd95 genes underlie the inhibitory effect of oxytocin on oxycodone-induced conditioned place preference

Oxycodone (Oxy) is one of the most effective analgesics in medicine, but is associated with the development of dependence. Recent studies demonstrating epigenetic changes in the brain after exposure to opiates have provided an insight into possible mechanisms underlying addiction. Oxytocin (OT), an endogenous neuropeptide well known for preventing drug abuse, is a promising pharmacotherapy to counteract addiction. Therefore, we explored the mechanism of Oxy addiction and the role of OT in Oxy-induced epigenetic alterations. In this study, drug-induced changes in conditioned place preference (CPP), i.e. the expression of synaptic proteins and synaptic density in the ventral tegmental area (VTA) were measured. We also sought to identify DNA methyltransferases (DNMTs), ten-eleven translocations (TETs), global 5-methylcytosine (5-mC), and DNA methylation of two genes implicated in plasticity (Synaptophysin, Syn; Post-synaptic density protein 95, Psd95). Oxy (3.0 mg/kg, i.p.) induced CPP acquisition in Sprague-Dawley rats. Oxy down-regulated DNMT1 and up-regulated TET1-3, leading to a decrease in global 5-mC levels and differential demethylation at exon 1 of Syn and exon 2 of Psd95. These changes in DNA methylation of Syn and Psd95 elevated the expression of synaptic proteins (SYN, PSD95) and synaptic density in the VTA. Pretreatment with OT (2.5 µg, i.c.v.) via its receptor specifically blocked Oxy CPP, normalized synaptic density, and regulated DNMT1 and TET2-3 causing reverse of DNA demethylation of Syn and Psd95. DNA methylation is an important gene regulation mechanism underlying Oxy CPP, and OT - via its receptor - could specifically inhibit Oxy addiction.