The effects of morphine in the consummatory contrast paradigm |
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Authors: | G A Rowan C F Flaherty |
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Institution: | (1) Department of Psychology, Rutgers University, 08903 New Brunswick, New Jersey, USA |
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Abstract: | Rats shifted from 32% to 4% sucrose show a negative contrast effect, licking significantly less than animals that receive
only 4% sucrose. The effects of morphine sulfate (0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/kg) on negative contrast were investigated
in four experiments. Contrast was reduced on both the 1st and 2nd postshift day by the 4.0 and 8.0 mg/kg doses, but the effects
were less robust than those seen with the benzodiazepines. The effects of morphine on contrast were dissociable from simple
increases in sucrose consumption. Naloxone (0.25, 0.5, and 1.0 mg/kg) had no effect on contrast or sucrose intake. However,
the contrast-reducing effect of morphine (4.0 mg/kg) was blocked by pretreatment with naloxone (0.50 mg/kg). The results are
discussed in terms of other anxiolytic screening paradigms that have obtained “partial anxiolytic effects” using morphine. |
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Keywords: | Morphine Incentive contrast Naloxone Anxiolytics |
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