The potency of fluvoxamine to reduce ethanol self-administration decreases with concurrent availability of food.

The selective serotonin reuptake inhibitor fluvoxamine reduces responding for ethanol at lower doses than responding for food when each is available in separate components or separate groups of rats. However, when both are available concurrently and deliveries earned per session are equal, this apparent selectivity inverts and food-maintained behavior is more sensitive than ethanol-maintained behavior to rate-decreasing effects of fluvoxamine. Here, we investigate further the impact concurrent access to both food and ethanol has on the potency of fluvoxamine. Fluvoxamine (5.6-17.8 mg/kg) potency was assessed under conditions where food and ethanol were available concurrently and response rates were equal (average variable intervals (VI) 405-s and 14-s for food and ethanol, respectively), as well as when density of food delivery was increased (average VI 60-s food & VI 14-s ethanol). The potency of fluvoxamine was also determined when only ethanol was available (food extinction and average VI 14-s ethanol) and under a multiple VI (VI 30-s food and ethanol) where either food or ethanol was the only programmed reinforcer available during each component. Fluvoxamine was less potent at decreasing ethanol self-administration when food was available concurrently (ED50 [95% C.L.]: 8.2 [6.5-10.3] & 10.7 [7.9-14.4]) versus when ethanol was available in isolation (ED50: 4.0 [2.7-5.9] & 5.1 [4.3-6.0]). Effects on food were similar under each condition where food was available. The results demonstrate that the potency of fluvoxamine to reduce ethanol-maintained behavior depends on whether ethanol is available in isolation or in the context of concurrently scheduled food reinforcement.