The influence of scopolamine on sucrose intake under absolute and relative test conditions

Becker

Checke

1983

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Contrast in consummatory behavior was investigated following repeated shifts from 32% to 4% sucrose. In Experiment 1, contrast in licking and in open-field measures of activity occurred following the second and third downshifts. In Experiments 2a and 2b, equivalent contrast effects occurred following the first and second downshifts in sucrose. In Experiment 3, negative contrast remained unabated following nine downshifts in animals shifted between 32% and 4% sucrose on alternate days. Similar results were found for five downshifts in animals shifted every 2 days. In both of these latter conditions, positive contrast occurred over the first few shifts and was then lost as the 32% control group reached asymptote. These data show that repeated negative contrast effects in consummatory behavior are robust and enduring and occur under several different sets of experimental parameters. The results are discussed in terms of reinforcement level and emotional interpretations of contrast effects, and the possibility was suggested that the causal mechanism of contrast changes with repeated shifts. Capaldi and Lynch (1967) reported that a successive negative contrast effect in runway behavior that occurred following a downshift in number of food pellets failed to recur when the animals were downshifted for a second time following a period of return to the initial reward conditions.

Section: Discussionmentioning

confidence: 99%

Repeated successive contrast in consummatory behavior with repeated shifts in sucrose concentration

Becker

Checke

1983

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“…Thus, to a greater or lesser degree, the anxiolytic agents CDP, midazolam, sodium amobarbital, ethanol, and morphine tend to reduce contrast (Becker, 1986;, 1983Flaherty, Becker, & Driscoll, 1982;Flaherty & Driscoll, 1980;Flaherty, Lombardi, Wrightson, & Deptula, 1980;. Nonanxiolytics, such as scopolamine, methysergide, pyrilamine, propranolol, and haloperidol, do not reduce contrast (Becker, 1986;Flaherty & Meinrath, 1979;Flaherty & Rowan, unpublished data).…”

mentioning

confidence: 99%

Chlordiazepoxide and the determinants of negative contrast

Grigson

Rowan-Szal

1986

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Previous experiments have shown that the negative contrast effect in consummatory behavior that occurs when rats are shifted from 32% to 4% sucrose is alleviated by the tranquilizer chlordiazepoxide (CDP). However, in these experiments, CDP was effective on the second postshift day but not on the first postshift day. The three experiments described in this paper suggest that this differential effectiveness of CDP is not due to the difference in preshift-postshift retention intervals on Day 1 (24 h) and Day 2 (48 h), but is due instead to the necessity of some degree of experience (about 5 min) with the postshift solution. These results, combined with those of an earlier study which showed elevated corticosterone in shifted animals on the second postshift day but not on the first postshift day, suggest that negative contrast may be a dynamic process, involving sequential processes of detection, evaluation, and conflict over the postshift period. It was further suggested that CDP becomes effective in moderating contrast only when the conflict stage is reached.Rats shifted from a 32 % to a 4 % sucrose solution consume substantially less of the 4 % sucrose than do rats that have experienced only the 4 % solution. This negative contrast effect that follows the shift in sucrose solutions is usually largest on the first postshift day and then declines so that, typically, by the fourth or fifth postshift day the shifted and unshifted animals are consuming approximately the same amount of 4% sucrose (e

“…Drugs that do not have anxiolytic effects in humans have thus far been found to be ineffective in reducing consummatory contrast. For example, contrast is not reduced by the anticholinergic scopolamine (Becker, 1984;Flaherty & Meinrath, 1979), the antihistamine pyrilamine (Becker, 1984), the antiserotonergic drug methysergide (Becker, 1984), or the neuroleptics haloperidol and chlorpromazine (unpublished data of Flaherty & Becker). .…”

mentioning

confidence: 99%

Correlation of corticosterone elevation and negative contrast varies as a function of postshift day

Becker

Pohorecky

1985

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In three experiments, rats shifted from 32% to 4% sucrose consumed less of the 4% sucrose than did rats that had received only the 4% solution. Experiment 1 showed that this negative contrast effect was not accompanied by a corticosterone elevation on the first day subsequent to the shift. Experiments 2 and 2a showed that corticosterone levels were substantially elevated on the 2nd postshift day and that there was a tendency for degree of elevation in corticosterone to be related to degree of lick suppression. These results are discussed in terms of other data suggesting that anxiolytic drugs and disinhibitory stimuli are more effective in alleviating contrast on the 2nd postshift day than on the 1st postshift day. It is suggested that, in the present paradigm, reaction to stimulus change may be the primary determinant of contrast on the 1st postshift day, but emotional processes related to reward loss and/or conflict develop by the 2nd postshift day.Rats shifted from a 32 % sucrose solution to a 4 % sucrose solution consume substantially less of the 4 % solution than animals that have experienced only 4 %sucrose.