Dopamine 'D2-like' receptor agonists in combination with cocaine: absence of interactive effects on locomotor activity
This study examined interactions between cocaine and drugs that act as direct agonists at subtypes of "D2-like" dopamine receptors. The drugs 7-OH-DPAT, quinpirole and RU24213 were studied alone and in combination with cocaine for their effects on locomotor activity in non-habituated mice....
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Published in | Behavioural pharmacology Vol. 8; no. 2-3; p. 147 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
England
01.06.1997
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Subjects | |
Online Access | Get more information |
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Summary: | This study examined interactions between cocaine and drugs that act as direct agonists at subtypes of "D2-like" dopamine receptors. The drugs 7-OH-DPAT, quinpirole and RU24213 were studied alone and in combination with cocaine for their effects on locomotor activity in non-habituated mice. Locomotor activity was measured by photobeam crossings over 140 min. At the doses given (7-OH-DPAT: 0.006-6.4 mg/kg; quinpirole: 0.001-1 mg/kg; RU24213: 0.008-8 mg/kg) all three direct agonists dose-dependently reduced locomotor activity throughout the test, whereas cocaine (0.6-20 mg/kg) produced dose-related hyperactivity. Next, for each direct agonist, a series of doses was selected (up to threshold behaviourally-active doses) as pretreatments to a sub-maximally stimulant dose of cocaine (15 mg/kg). 7-OH-DPAT and quinpirole did not modulate the effects of cocaine; RU24213 produced, at best, a very modest attenuation of the effects of cocaine. Finally, a series of cocaine doses (below stimulant threshold) was given before a single dose of each direct agonist (the lowest dose to reduce activity significantly). Cocaine did not reliably alter the hypoactivity produced by any of the D2-like agonists. By demonstrating negligible interactions between cocaine and D2-like agonists, the results fail to demonstrate any necessary involvement of D2-like receptors in one of the behavioural effects of cocaine. |
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ISSN: | 0955-8810 |