Dietary additives and the acquisition of cocaine self-administration in rats

Abstract

The effects of dietary caffeine and the amount and palatability of food on the acquisition of cocaine (0.2 mg/kg) self-administration were examined. Using an autoshaping procedure, seven groups of 13 rats each were trained to press a lever resulting in a cocaine (0.2 mg/kg infusion under a fixed-ratio 1 (FR 1) schedule. One group had ad libitum access to caffeine- (0.2% w/w) admixed food. Three groups had access to 10 g, 20 g or ad lib food each day. Another three groups had the same three amounts of ground food with powdered saccharin (0.2% w/w) added. During daily 6-h autoshaping sessions, ten infusions were delivered each hour under a random-time 90-s schedule after a brief (15 s) extension of a retractable lever. These were followed by 6-h self-administration sessions, when the lever remained extended and cocaine infusions were available under an FR 1 schedule. The acquisition criterion was self-administration of a mean of 100 infusions over 5 days. Cocaine self-administration was accelerated in the caffeine group compared to the regular chow group. However, by 30 days nearly the same percentage of rats in the caffeine and regular food groups met the acquisition criterion. In the other six groups, as the amount of food increased, the rate of acquisition and percentage of rats per group meeting the acquisition criterion decreased. In the ad lib group, acquisition was further reduced when saccharin was added to food. In summary, dietary caffeine accelerated acquisition and a greater amount and increased palatability of food independently interfered with acquisition of cocaine self-administration in rats.

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“…The present data are supported by previous data from this and other laboratories with a variety of different behavioral assays in which caffeine was studied at the moderate dose to enhance, increase or potentiate the effects of cocaine (62)(63)(64)(65). Further evidence for attributing potentiated effects of caffeine on cocaine to caffeine's moderate dose, comes from data which show that low and high doses of caffeine are neuroprotective against cocaine-induced DA-ergic neurotoxicity (66,67).…”

Effects of Adolescent Caffeine Consumption on Cocaine Sensitivity

“…These findings are in opposition to other studies where acute treatment with caffeine in adult animals increases the development of cocaine CPP (Bedingfield et al, 1998), augments cocaine-induced locomotor activity (Horger et al, 1991;Misra et al, 1986), and results in amplified activation of the mesolimbic dopamine system (Horger et al, 1991). Likewise, chronic caffeine exposure in adult animals increased locomotor activity to cocaine (Gasior et al, 2000;Schenk et al, 1990) and facilitated acquisition of cocaine self-administration (Carroll and Lac, 1998). Many of these studies use higher doses of caffeine as well as shorter exposure lengths both of which could produce different effects.…”

Sucrose intake predicts rate of acquisition of cocaine self-administration

“…Pre-exposure to amphetamine or nicotine facilitated the acquisition of cocaine self-administration; beyond the first eight sessions, the treatment groups were not different from a control group (Horger et al 1992). Similarly, Carroll and Lac (1998) found that the addition of caffeine or saccharin to the maintenance diet accelerated or slowed, respectively, the acquisition of cocaine self-administration, but that cocaine intake after the acquisition criterion was met did not differ among the groups. They suggest that it may be useful to target this acquisition period in efforts to prevent drug abuse.…”

“…The day of acquisition was defined as the last day of a 3-day period in which the mean number of self-administered infusions was at least 25. This number represents approximately one-half the mean number of infusions obtained by day 10 and is equivalent to the criterion number of infusions used by Carroll and Lac (1998) when adjusted for the duration of the daily sessions. Fourteen of 16 rats (88%) met this criterion for acquisition.…”