AN INFANT MODEL OF ETHANOL SELF-ADMINISTRATION: INVOLVEMENT OF THE OPIOID SYSTEM.

MIRANDA MORALES RS; MOLINA JC; ABATE P

SAN ANTONIO, TEXAS, EEUU

Congreso; 2010 Scientific Meeting of the Research Society on Alcoholism.; 2010

RESEARCH SOCIETY ON ALCOHOLISM

The main goal of this study was to analyze appetitive and consumatory behaviors in an infant model of ethanol self-administration. Through the use of a non-selected antagonist, we evaluated how the opioid system modulates such behaviors. In a first experiment infant rats (PD14) were trained in an operant learning task to obtain sucrose 5% (Group 1), ethanol 3.75% (Group 2) or distilled water (Group 3). Yoked control pups received the reinforcer each time the experimental pup was rewarded. Each training session was performed in 15 minute, during 4 consecutive days (PD’s 14, 15, 16 and 17). On PD18 infants were evaluated in an extinction session. All experimental pups rapidly acquired an operant response across training days to gain access to the reinforcers. Paired pups significantly increased operant responses in comparison with yoked animals. Even when water elicited operant behavior, sucrose and ethanol promoted higher levels of responses than this liquid. When analyzing operant behavior, in the extinction session, paired pups previously infused with sucrose or ethanol executed a significant higher number of operant responses than pups infused with water (whose operant behavior was not different to the control pup). In a second experiment we evaluated the involvement of the opioid system in the pattern of infantile operant behavior mediated by ethanol and sucrose. Pups were trained in a similar operant learning task to obtain sucrose 5% (Group 1) or ethanol 3.75% (Group 2). At PDs 16 and 17, previous operant session, animals were briefly re-exposed to sucrose or ethanol (5 minute of pulsatile infusions, 1.5 second each) under opioid antagonism (naloxone) effects. Operant responding for sucrose or ethanol was then assessed. As previously observed, paired pups learned an operant behavior either, for ethanol or sucrose. Nonetheless, during PDs 16 to 17, those pups re-exposed to the reinforcer, under the effects of naloxone, failed to increase their operant response (neither for sucrose or ethanol), in comparison with their yoked controls. During extinction session, only a significant effect of learning condition was observed. Independently from the reinforcer received, paired pups elicited significantly more responses than yoked controls. These experiments indicate that ethanol and sucrose are potent reinforcers during infancy. The participation of the opioid system was possible to be observed only during the acquisition phase of this operant learning task.