Oxytocin (80 ng) injected into the caudal region of the ventral tegmental area (VTA) induces penile erection in male rats. This response occurs with an increase in extra-cellular dopamine concentration in the dialysate obtained from the nucleus accumbens by intracerebral microdialysis. Both responses are reduced by the oxytocin antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 µg) given into the VTA, while penile erection, but not the increase of extra-cellular dopamine, is reduced by the dopamine antagonist haloperidol (1 µg) given into the nucleus accumbens. Oxytocin responses are also reduced by the nitric oxide (NO) synthase inhibitor L-NAME (20 µg) and by the soluble guanylate cyclase inhibitor ODQ (40 µg), given in the caudal VTA. Increases in penile erection and in extra-cellular dopamine in the nucleus accumbens dialysate similar to those induced by oxytocin are induced by 8-bromo-cyclic GMP (3 µg) injected into the VTA. These results suggest that oxytocin in the VTA activates mesolimbic dopaminergic neurons by acting on receptors located in the cell bodies of dopaminergic neurons and coupled to a NO-cGMP signalling pathway. Penile erection and extra-cellular dopamine concentration increase in the nucleus accumbens dialysate also occur when the dopamine agonist apomorphine (100 ng) is injected into the paraventricular nucleus of the hypothalamus (PVN), and both these responses are reduced by haloperidol (1 µg) given into the PVN and by d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 µg) given into the VTA. Together with immunoistochemistry studies showing that oxytocinergic synapses impinge on the cell bodies of mesolimbic dopaminergic neurons positive for both NO synthase and guanylate cyclase in the VTA, these results show that oxytocinergic neurons projecting from the PVN to the caudal VTA contribute to the activation of mesolimbic dopaminergic neurons which are activated during the anticipatory phase of sexual behaviour. This supports the existence of a neural circuitry in which central oxytocinergic neurons play a role not only the consummatory phase of sexual behaviour (oxytocinergic neurons projecting to the spinal cord and to the genital apparatus), but also the anticipatory phase of sexual behaviour (oxytocinergic neurons projecting to the VTA).

The role of oxytocin in the anticipatory and consummatory phases of male rat sexual behaviour

MELIS, MARIA ROSARIA;SANNA, FABRIZIO;ARGIOLAS, ANTONIO
2009-01-01

Abstract

Oxytocin (80 ng) injected into the caudal region of the ventral tegmental area (VTA) induces penile erection in male rats. This response occurs with an increase in extra-cellular dopamine concentration in the dialysate obtained from the nucleus accumbens by intracerebral microdialysis. Both responses are reduced by the oxytocin antagonist d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 µg) given into the VTA, while penile erection, but not the increase of extra-cellular dopamine, is reduced by the dopamine antagonist haloperidol (1 µg) given into the nucleus accumbens. Oxytocin responses are also reduced by the nitric oxide (NO) synthase inhibitor L-NAME (20 µg) and by the soluble guanylate cyclase inhibitor ODQ (40 µg), given in the caudal VTA. Increases in penile erection and in extra-cellular dopamine in the nucleus accumbens dialysate similar to those induced by oxytocin are induced by 8-bromo-cyclic GMP (3 µg) injected into the VTA. These results suggest that oxytocin in the VTA activates mesolimbic dopaminergic neurons by acting on receptors located in the cell bodies of dopaminergic neurons and coupled to a NO-cGMP signalling pathway. Penile erection and extra-cellular dopamine concentration increase in the nucleus accumbens dialysate also occur when the dopamine agonist apomorphine (100 ng) is injected into the paraventricular nucleus of the hypothalamus (PVN), and both these responses are reduced by haloperidol (1 µg) given into the PVN and by d(CH2)5Tyr(Me)2-Orn8-vasotocin (1 µg) given into the VTA. Together with immunoistochemistry studies showing that oxytocinergic synapses impinge on the cell bodies of mesolimbic dopaminergic neurons positive for both NO synthase and guanylate cyclase in the VTA, these results show that oxytocinergic neurons projecting from the PVN to the caudal VTA contribute to the activation of mesolimbic dopaminergic neurons which are activated during the anticipatory phase of sexual behaviour. This supports the existence of a neural circuitry in which central oxytocinergic neurons play a role not only the consummatory phase of sexual behaviour (oxytocinergic neurons projecting to the spinal cord and to the genital apparatus), but also the anticipatory phase of sexual behaviour (oxytocinergic neurons projecting to the VTA).
2009
978-1-60876-023-7
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11584/95550
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