Food‐deprivation Level Alters the Effects of Morphine on Pigeons' Key Pecking

Abstract

Four pigeons pecked response keys under a multiple fixed-ratio 30 fixed-interval 5-min schedule of food presentation. Components alternated separated by 15-s timeouts; each was presented six times. Pigeons were maintained at 70%, 85%, and greater than 90% of their free-feeding weights across experimental conditions. When response rates were stable, the effects of morphine (0.56 to 10.0 mg/kg) and saline were investigated. Morphine reduced response rates in a dose-dependent manner under the fixed-ratio schedule and at high doses under the fixed-interval schedule. In some cases, low doses of morphine increased rates under the fixed-interval schedule. When pigeons were less food deprived, reductions in pecking rates occurred at lower doses under both schedules for 3 of 4 birds compared to when they were more food deprived. When pigeons were more food deprived, low doses of morphine increased rates of pecking in the initial portions of fixed intervals by a greater magnitude. Thus, food-deprivation levels altered both the rate-decreasing and rate-increasing effects of morphine. These effects may share a common mechanism with increased locomotor activity produced by drugs and with increased drug self-administration under conditions of more severe food deprivation.

A mouse model for binge-like sucrose overconsumption: Contribution of enhanced motivation for sweetener consumption

“…The difference between sucrose and saccharin may be due to the postingestive nutritive action of sucrose [16,50], suggesting that caloric sucrose has a strong propensity to reinforce uncontrolled eating such as binge-like overconsumption under food restriction conditions. Food deprivation affects not only food consumption, but also enhances addictive behavior for drugs of abuse [59,60] and the rewarding effects of food [53,61]. How food restriction can drive neuronal changes underlying binge-like behaviors remains to be identified, although some clues are emerging.…”

Effects of D‐amphetamine in a Temporal Discrimination Procedure: Selective Changes in Timing or Rate Dependency?

“…The subjects were 4 adult male White Carneau pigeons with previous acute exposure to cocaine (Schaal, Miller, & Odum, 1995) and morphine (Odum, Haworth, & Schaal, 1998;Odum & Schaal, 1999) while responding under a multiple fixed-ratio FI schedule or a multiple FI clocked FI schedule of food presentation. The pigeons were maintained at 80% (Ϯ 10 g) of their free-feeding weights through postsession feedings of mixed grain as necessary.…”

Disruption of Temporally Organized Behavior by Morphine

“…The peak procedure was selected because of its similarity to the FI schedule. We reasoned that any drug that alters FI schedule performance in a rate-dependent fashion, including morphine (Heifetz & McMillan, 1971;Katz & Goldberg, 1986;McKearney, 1974;Odum, Haworth, & Schaal, 1998;Odum & Schaal, 1999Rhodus, Elsmore, & Manning, 1974), should also alter performance on the PI trials, at least in the early portion of these trials. The two-key task, on the other hand, is seemingly not similar to the FI schedule.…”