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- Effects of neonatal exposure to methamphetamine: Catecholamine levels in brain areas of the developing ratPublication . Silva, Joana Gomes da; Miguel, Rosário de; Fernández-Ruiz, Javier; Summavielle, Teresa; Tavares, M. Amélia; Summavielle, TeresaNeonatal exposure to moderate doses of methamphetamine during the first month of life in the rat affects tyrosine hydroxylase gene expression in the substantia nigra and nigrostriatal tyrosine hydroxylase activity. The main goal of this work was to evaluate the ontogeny of the neurochemical effects of repeated exposure to moderate doses of methamphetamine during the first month of life in the rat. Norepinephrine, dopamine, and dihydroxyphenylacetic acid levels were measured in target areas of methamphetamine: the substantia nigra, ventral tegmental area, caudate-putamen, nucleus accumbens, and medial prefrontal cortex. On postnatal day 1 (PND1), Wistar rat litters, culled to eight pups, sex balanced, were randomly attributed to either methamphetamine or control groups. Methamphetamine groups were administered 10 mg of (±)-methamphetamine/kg body weight/day, subcutaneously, from PND1 until the day prior to sacrifice; control groups received isovolumetric saline. Groups were sacrificed on PND7, PND14, and PND30. Neonatal methamphetamine exposure increased norepinephrine levels in the substantia nigra of PND30 rats; on PND14, this variation was evident only in male pups. In the substantia nigra, the dihydroxyphenylacetic/dopamine ratio was also affected in PND30 males. In the ventral tegmental area, catecholamine levels were not affected by methamphetamine. Norepinephrine levels were also increased in the caudate-putamen of PND7 male and PND14 female methamphetamine-exposed pups and in the nucleus accumbens of PND14 female and PND30 male and female pups. Catecholamine levels in the medial prefrontal cortex were not affected by neonatal methamphetamine administration.
- Effects of postnatal cocaine exposure and environmental enrichment on rat behavior in a forced swim testPublication . Magalhães, Ana; Summavielle, Teresa; Tavares, Maria Amélia; Sousa, Liliana de; Summavielle, TeresaThis study examined the effects of environmental enrichment on rats exposed to cocaine during the first month of life, in several categories of behavior observed in a forced swim test. Wistar rats were divided in four groups. The first included pups that were subjected to injections of cocaine hydrochloride (15 mg/kg body weight/day, subcutaneously, in two daily doses, from postnatal days 1 to 27) and reared in an enriched environment (CocEE); the second, pups that were subjected to injections of cocaine (as previously described) and reared in a standard environment (CocSE); the third, pups that were subjected to saline injections and reared in an enriched environment (SalEE); the fourth, pups that were subjected to saline injections and reared in a standard environment (SalSE). On postnatal days 26 and 27, rats were tested in a swimming pool in two 5-min sessions. The categories of behavior studied in this work were: fast swim, slow swim, struggling, diving, and immobility. Results showed that postnatal cocaine exposure decreased the time spent on fast swim during the two sessions and increased the immobility behavior during the second session in CocSE pups compared with SalSE pups. SalEE pups increased the time spent in fast swim, slow swim, and diving, and decreased the time spent in struggling and immobility during the two sessions compared with SalSE pups. CocEE animals spent more time in fast swim and struggling and less the time in immobility compared with CocSE pups. The present results suggest that postnatal cocaine exposure affects the ability of these animals to cope with stressful situations, and that environmental enrichment seems to enable the rats to adopt a more active strategy, one that allows them to better cope with this particular stress situation.