Reinforcement magnitude modulates the rate-dependent effects of fluvoxamine and desipramine on fixed-interval responding in the pigeon

Abstract

Some doses of fluvoxamine can decrease ethanol-maintained behavior more than food-maintained behavior. This might be explained by differences in reinforcement magnitude. In a previous study, the effects of fluvoxamine on fixed-ratio responding did not depend upon reinforcement magnitude. Response rates, however, differed with reinforcement magnitude. These differences in response rates might explain the failure to observe differences in the potency of fluvoxamine with changes in reinforcement magnitude. In this study, we examined whether the effects of fluvoxamine and desipramine depended on the reinforcement magnitude and response rate, by administering these drugs to pigeons responding under a multiple fixed-interval schedule, in which responding in three components was maintained by differing durations of food presentation (2, 4, and 8 s). The effects of fluvoxamine and desipramine depended jointly on control rate, reinforcement magnitude, and dose. Low fluvoxamine doses had rate-dependent effects in all three components, increasing lower rates more than higher rates: as dose increased, these rate-dependent effects became greater in the components maintained by the 2-s or 4-s food presentation; whereas, in the component maintained by the 8-s presentations, they declined. Low desipramine doses had rate-dependent effects only in the component maintained by the 2-s presentations, whereas higher doses had rate-dependent effects in components maintained by 2-s or 4-s presentations. Still higher doses had rate-dependent effects in all the three components. Although the effects of fluvoxamine and desipramine might not depend on reinforcement magnitude when studied under fixed-ratio schedules, reinforcement magnitude can modulate their effects when they are studied over a wider range of control response rates.

Relative Potency of Varenicline or Fluvoxamine to Reduce Responding for Ethanol Versus Food Depends on the Presence or Absence of Concurrently Earned Food

“…However, we have demonstrated that fluvoxamine effects are unlikely to depend on the magnitude of reinforcement (Lamb and Ginsburg, 2005, 2008; Ginsburg and Lamb, 2008). The extent to which varenicline effects could be influenced by the relative frequencies of reinforcement remains unknown.…”

The generality of nicotine as a reinforcer enhancer in rats: effects on responding maintained by primary and conditioned reinforcers and resistance to extinction

“…A recent study showed that nicotine also increased the number of completed ratios on a progressive ratio schedule of visual stimulus presentation (Chaudhri et al 2007), suggesting that nicotine does more than merely increase low response rates. Nevertheless, more research will be necessary to test whether nicotine increases low rates of responding or whether such increases are specific to parameters of the reinforcing stimuli (Lamb and Ginsburg 2008).…”

Reinforcement magnitude modulation of rate-dependent effects of fluvoxamine and desipramine in the rat

“…Work performed with pigeons demonstrated that reinforcement magnitude can modulate the rate-dependent effects of fluvoxamine and desipramine (Lamb and Ginsburg, 2008). In that study, pigeons responded under a multiple fixed-interval schedule reinforced by 2-, 4-, or 8-sec access to food.…”