Differential effects of novelty exposure on place preference conditioning to amphetamine and its oral consumption.

RATIONALE

Sensation/novelty seeking is frequently observed in drug abusers. Rats with high locomotor activity in response to inescapable novelty may be more prone to drug addiction. However, it is not clear whether this response to novelty represents reactivity to the novelty-induced stress or seeking for novelty.

OBJECTIVES

We have compared the influence of the response to novelty-presented in a forced stressful or in a free choice non-stressful manner-on vulnerability to addictive properties of amphetamine.

METHODS

Wistar rats were selected according to their (i) reactivity to inescapable novelty and (ii) novelty preference. For this purpose, animals were exposed during two 30-min sessions, 24 h apart, to the same compartment; their motor activity during the first session was used as an index of reactivity. On the third day, they were allowed to choose between this "familiar" environment and a novel one. Rewarding properties of amphetamine (0.2-3.2 mg/kg, s.c.) were determined by place conditioning. Amphetamine oral consumption (10-50 mg/l) in a free-choice paradigm was measured over a period of 32 days.

RESULTS

Reactivity to novelty and novelty preference were not correlated. Reactivity to inescapable novelty predicted place conditioning induced by the lowest dose of amphetamine, whereas preference for novelty did not. High responders to inescapable novelty consumed less amphetamine than low responders. Novelty preference was positively correlated to amphetamine oral consumption only at the lowest concentration.

CONCLUSIONS

Reactivity to inescapable novelty and novelty preference represent different behavioural components, which are related differentially with amphetamine place conditioning and its oral consumption.