Exposição a nicotina durante o período pós-natal e na fase adulta: efeitos na atividade locomotora e na neuroplasticidade de camundongos Swiss

Abstract

Smoking is a public health problem which affects 25% of pregnant women. Previous studies show that the exposure to tobacco smoke during the early postnatal period interferes with processes related to the brain development. Thus, the aim of this study was to assess whether the exposure to nicotine during the early postnatal period has an effect on the behavioural sensitization to nicotine during adulthood. For this reason, male Swiss mice were exposed to nicotine between the postnatal day (PN 4) and (PN 17) by osmotic mini pumps implanted in the mothers (8 mg/kg/day). In the adulthood, the mice were treated with nicotine (1 mg/kg, i.p.) or saline solution for seven alternate days (D1, D3, D5, D7, D9 e D13) to acquire sensitization. On the third day of abstinence, the elevated plus-maze test was performed to evaluate anxiety. In D18 the mice were challenged with saline or nicotine. After the behavioural tests, the animals were euthanized and the c-Fos, Synapsin I and PSD-95 proteins were quantified by Western blot in different brain structures. There was a decrease in locomotor activity in animals that received nicotine in D1 when compared to those that received saline. The animals in the SAL postnatal NIC/NIC groups showed an increased locomotor activity between D1 and D13, while the animals in the NIC postnatal NIC/NIC group showed an increased locomotor activity between D1 and D13 and between D1 and the day of the challenge. In the elevated plus maze test, animals in the NIC postnatal NIC/NIC group showed an increase in the time and in the number of open arms entries compared to animals in the SAL postnatal NIC/NIC group in addition to a decrease in rearing compared to animals that received saline in adulthood. The results show that there was a decrease in the c-Fos levels in the cerebellum and striatum in the NIC postnatal SAL/SAL, SAL postnatal NIC/NIC, and NIC postnatal NIC/NIC when compared with SAL postnatal SAL/SAL. The results show that the dose of nicotine used during adulthood was not able to induce a behavioural sensitization although the exposure to nicotine in the early postnatal period contributed to the increase in the locomotor activity on the day of the challenge and to the decrease in anxiety during the withdrawal period. The exposure to nicotine, both in the early postnatal period and in adulthood, was able to induce a decrease in c-Fos in the cerebellum and striatum.