Low- and high-ethanol doses shifts the appetitive hedonic value of a natural reinforcer in infant rats: inflation and deflation effects.

CULLERÉ, ME; PAUTASSI, RM; PONCE, LF; SPEAR, NE; ABATE, PAULA; MOLINA, JC

SAN DIEGO, EEUU

Congreso; 2009 Scientific Meeting of the Research Society on Alcoholism. RSA, EEUU; 2009

RESEARCH SOCIETY ON ALCOHOLISM

Reinforcing properties of ethanol are perceived early in life. Infant rats express appetitive and aversiveethanol-mediated learning. Appetitive effects are more easily observed at low doses (£0.5 g/kg) andwhen the conditioning procedure is conducted during the early phase of the intoxication; while aversiveeffects seem prominent at higher doses (‡2.0 g/kg) and late during the course of the intoxication(Molina, Pautassi, Truxell and Spear, 2007). The interaction between ethanol’s unconditional propertiesand the hedonic attributes of natural reinforcers, however, has yet to be addressed. This study aimedat assessing if acute ethanol can shift (i.e., inflate) the motivational properties of a natural sapid reinforcer.In Experiment 1, infant rats (postnatal days - PD - 14 to 15) were trained in an operant taskwhere nose poke behavior was reinforced with an intraoral infusion of sucrose (10% w/v). Ethanol wasadministered immediately after each training session (0.0, 0.25, 0.5 or 1.5 g/kg). On PD 16 (test), animalsthat had been given 0.25 g/kg ethanol on PDs 14-15 exhibited more sucrose-reinforced operantbehavior than control pups; while pups treated with 1.5 g/kg ethanol exhibited a significant decrease inresponding for sucrose. In Experiment 2, pups were trained to nose poke (PD 14, 15 and 16) forsucrose (5% w/v, Exp 2A; 10% w/v, Exp 2B). At PD17 animals were briefly re-exposed to sucrose (4infusions, 3 sec each, ISI 57 s) while experiencing the onset of an ethanol intoxication state (0.5 or 0.0g/kg, US re-evaluation session). Operant responding for sucrose was then assessed. Pups given reexposureto sucrose while intoxicated exhibited significantly more nose-poke responding than controls(Exp. 2B), a result that persisted even after withdrawing the reinforcer (i.e., extinction sessions, Exp. 2Aand 2B) These results indicate that ethanol’s post-absorptive consequences can effectively shift (i.e.,inflate or deflate) the reinforcing value of sucrose. The direction of this outcome seems to depend onappetitive and aversive attributes of the drug associated with low- and high-ethanol doses, respectively.These results are congruent with previous observations (Molina et al., 2006; 2007; Pautassi et al.,2006) indicating early ethanol-mediated reinforcement in the rat.