Food restriction increases acquisition, persistence and drug prime-induced expression of a cocaine-conditioned place preference in rats.

Cocaine conditioned place preference (CPP) is more persistent in food-restricted than ad libitum fed rats. This study assessed whether food restriction acts during conditioning and/or expression to increase persistence. In Experiment 1, rats were food-restricted during conditioning with a 7.0 mg/kg (i.p.) dose of cocaine. After the first CPP test, half of the rats were switched to ad libitum feeding for three weeks, half remained on food restriction, and this was followed by CPP testing. Rats tested under the ad libitum feeding condition displayed extinction by the fifth test. Their CPP did not reinstate in response to overnight food deprivation or a cocaine prime. Rats maintained on food restriction displayed a persistent CPP. In Experiment 2, rats were ad libitum fed during conditioning with the 7.0 mg/kg dose. In the first test only a trend toward CPP was displayed. Rats maintained under the ad libitum feeding condition did not display a CPP during subsequent testing and did not respond to a cocaine prime. Rats tested under food-restriction also did not display a CPP, but expressed a CPP following a cocaine prime. In Experiment 3, rats were ad libitum fed during conditioning with a 12.0 mg/kg dose. After the first test, half of the rats were switched to food restriction for three weeks. Rats that were maintained under the ad libitum condition displayed extinction by the fourth test. Their CPP was not reinstated by a cocaine prime. Rats tested under food-restriction displayed a persistent CPP. These results indicate that food restriction lowers the threshold dose for cocaine CPP and interacts with a previously acquired CPP to increase its persistence. In so far as CPP models Pavlovian conditioning that contributes to addiction, these results suggest the importance of diet and the physiology of energy balance as modulatory factors.

Polyunsaturated fatty acid status and aggression in cocaine addicts.

BACKGROUND: There is mounting evidence that low levels of some polyunsaturated fatty acids (PUFAs) play a role in the pathophysiology of aggressive disorders. PUFA status is influenced by nutritional factors and because of our observation that some substance abusers have poor dietary habits, we explored the possibility that the fatty acids (FA) profiles of cocaine addicts with and without aggressive tendencies would differ. We also explored the possibility that their FA levels would change after a 2 week stay on an inpatient unit where a standard diet would be provided. METHODS: Plasma levels of FAs were measured in 24 cocaine addicts admitted to an inpatient substance abuse unit. Six patients had a past history of aggression and 18 did not. RESULTS: A comparison of the FA levels of aggressive and non-aggressive patients performed 3.7+/-2.0 days after their admission did not reveal any significant difference in saturated FAs (SFAs) or monounsaturated FAs (MFAs). Aggressive patients had significantly lower levels of the n-6 PUFA docosapentaenoic acid (DPA), of total n-3 PUFAs and of the n-3 PUFA docosahexaenoic acid (DHA), and a marginally significant increase in the ratio of n-6 to n-3 PUFAs. Measurements performed 18.4+/-1.3 days after admission showed that most FAs had increased in the two patient groups. Some PUFAs, especially those of the n-3 series, increased more sharply in the aggressive patients. As a result, PUFA differences between groups that were present shortly after admission became non-significant. CONCLUSIONS: These data suggest that patients' diets prior to their hospitalization were less than optimal and that the diet of the aggressive individuals might have been particularly deficient in n-3 rich nutrients. These data also give additional support to evidence indicating a possible link between an n-3 deficiency and aggression in humans.