Oxytocin injected into the ventral tegmental area induces penile erection and increases extracellular dopamine in the nucleus accumbens and paraventricular nucleus of the hypothalamus of male rats

Abstract

The neuropeptide oxytocin (20-100 ng), induces penile erection when injected unilaterally into the caudal but not rostral mesencephalic ventral tegmental area (VTA) of male Sprague-Dawley rats. Such pro-erectile effect started 30 min after treatment and was abolished by the prior injection of d(CH2)5Tyr(Me)(2)-Orn(8)-vasotocin (1 microg), an oxytocin receptor antagonist injected into the same caudal ventral tegmental area or of haloperidol (1 microg), a dopamine receptor antagonist, injected either into the nucleus accumbens shell (NAs) or into the paraventricular nucleus of the hypothalamus (PVN) ipsilateral to the injected ventral tegmental area. Penile erection was seen 15 min after the occurrence of, or concomitantly to, an increase in extracellular dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the dialysate obtained from the nucleus accumbens or the paraventricular nucleus, which was also abolished by d(CH2)5Tyr(Me)(2)-Orn(8)-vasotocin (1 microg), injected into the ventral tegmental area before oxytocin. In the caudal ventral tegmental area oxytocin-containing axons/fibres (originating from the paraventricular nucleus) appeared to closely contact cell bodies of mesolimbic dopaminergic neurons retrogradely labelled with Fluorogold injected into the nucleus accumbens shell, suggesting that oxytocin effects are mediated by the activation of mesolimbic dopaminergic neurons, followed in turn by that of incerto-hypothalamic dopaminergic neurons impinging on oxytocinergic neurons mediating penile erection. As the stimulation of paraventricular dopamine receptors not only induces penile erection, but also increases mesolimbic dopamine neurotransmission by activating oxytocinergic neurons, these results provide further support for the existence of a neural circuit in which dopamine and oxytocin influence both the consummatory and motivational/rewarding aspects of sexual behaviour.

Evidence That Oxytocin Exerts Anxiolytic Effects via Oxytocin Receptor Expressed in Serotonergic Neurons in Mice

“…TH is the catecholamine synthetic enzyme and a maker molecule of dopaminergic, adrenergic, and noradrenergic cells. OXT has been reported to facilitate release of noradrenaline and dopamine within the brain (Lévy et al, 1995;Onaka et al, 2003;Melis et al, 2007). We examined whether Venus-positive neurons express TH immunoreactivity in the glomerular layer of the olfactory bulb (Gl) (the A16 dopaminergic cell region) (Fig.…”

Mechanisms of Penile Erection and Basis for Pharmacological Treatment of Erectile Dysfunction

“…This may occur also in humans, because plasma oxytocin is increased by sexual stimuli, especially at ejaculation (Carmichael et al, 1987;Murphy et al, 1987). Oxytocin induces penile erection not only when injected into the lateral cerebral ventricle and the PVN but also in other extrahypothalamic brain regions, such as the ventral tegmental area (Melis et al, 2007(Melis et al, , 2009Succu et al, 2008), the ventral subiculum of the hippocampus, and the posterior nucleus of the amygdala (Melis et al, 2009(Melis et al, , 2010, which are important constituents of the limbic system and are thought to play a key role in motivation and reward processes. The erectile response was blocked by oxytocin antagonists and by electrolytic lesion of the PVN.…”

Rol Modulador de la Oxitocina en la Interacción Social y el Estrés Social

“…En machos está implicada en: el funcionamiento eréctil (Melis et al, 2010;Succu et al, 2008;Melis et al, 2007), la actividad copulatoria y la eyaculación (Gil, Bhatt, Picotte, & Hull, 2011). Es importante aclarar que la OT no actúa de forma individual, ésta debe interactuar con otras hormonas como por ejemplo la testosterona, pues si un macho se encuentra castrado a pesar de suministrarle OT no podrá tener erecciones (Connor & Heithaus, 1996).…”