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The anteroventral periventricular nucleus (AVPV) is sexually dimorphic, presenting a higher neuronal density in females. The AVPV contains a dense collection of oestrogen and progesterone receptors and has been related to the modulation of gonadotrophin-releasing hormone (GnRH) secretion and gene expression in response to circulating hormonal levels. It has been suggested that cocaine- and amphetamine-regulated transcript (CART) is also related to reproductive control because CART immunoreactive fibres are in close apposition with GnRH neurones. A portion of these fibres originate in the AVPV but its role in mediating hormonal action needs to be better explored. We hypothesised that CART expression in the AVPV would be influenced by the reproductive state and, consequently, by hormonal levels. To test this hypothesis, we analysed CART expression in the AVPV of female rats in different reproductive states (pro-oestrous, pregnancy and lactation). We found that, on the 19th day of pregnancy, female rats presented increased CART expression. Our findings indicate that AVPV CART expression is influenced by the reproductive state and that CART neurones in the AVPV may play a role in the hormonal mechanisms involved in the induction of maternal behaviour.

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