Learning during early ontogeny: Involvement of the opioid system in modulating ethanol-mediated reinforcing aspects

ABATE P; REYES GUZMAN A.C.; HERNANDEZ FONSECA K.; GUTTLEIN L; MÉNDEZ UBACH M.

Puebla

Simposio; 1st Neurobiology Meeting, 2016 Sociedad Mexicana de Bioquímica, A.C. Puebla, Pue., México; 2016

Sociedad Mexicana de Bioquímica - Rama de Neurobiología

Ethanol self-administration and seeking behaviors are modulated by the action of the opioid system, during early ontogeny. Prenatal blockade of the opioid system, before ethanol administration, inhibited the expected increase in ethanol-related appetitive and consummatory behaviors in neonate and infant rats. During infancy, subjects also rapidly learn to self-administer ethanol under an operant conditioned paradigm; opioid system is involved in ethanol reinforcing mechanisms. We found, employing a pharmacological approach that mu, delta and kappa opioid receptors have to be active to promote positive ethanol reinforcement in infants. We will show evidences that a high ethanol affinity occurs during early ontogeny and that this preference implies a fully functional opioid system. In addition, we investigated the effect of prenatal ethanol exposure and infantile alcohol intake, in Methionine-enkephalin (Met-enk) contents in the ventral tegmental area [VTA], nucleus accumbens [NAcc], prefrontal cortex [PFC], substantia nigra [SN], caudate-putamen [CP], amygdala, hypothalamus and hippocampus. Infantile Met-enk content in PFC and NAcc was increased as a consequence of prenatal exposure to ethanol. Conversely, Met-enk levels in the VTA were reduced by prenatal ethanol manipulation. Prenatal ethanol also increased peptide levels in the medial-posterior CP, hippocampus and hypothalamus. These findings show that prenatal ethanol exposure induces changes in behavioral parameters that could be mediated by Met-enk levels in regions of the mesocorticolimbic and nigrostriatal systems, hypothalamus and hippocampus. These results support the role of mesocorticolimbic enkephalins in ethanol reinforcement in infancy, as has been reported in adults. This work was supported by grants from ANPCyT (PICT 2011-0130); CONICET and SECyT-UNC {PA} and CONACyT 34359-N, Mexico {MM}.