The influence of central administration of dopaminergic and cholinergic agents
on morphine-induced amnesia in morphine-sensitized mice
Mohammad-Reza Zarrindast1*,
Maryam Farahmandfar2,
Parvin Rostami3,
Ameneh Rezayof4
1 Department of Pharmacology and Iranian National Center for Addiction
Studies, Tehran University of Medical Sciences, Tehran, Iran and School of
Cognitive Science, Institute for Studies in Theoretical Physics and Mathematics,
Tehran, Iran.
2 Department of Pharmacology and Iranian National Center for Addiction
Studies, Tehran University of Medical Sciences, Tehran, Iran.
3 Department of Biology, Teacher Training University, Tehran, Iran.
4 Department of Biology, Faculty of Science, Tehran University, Tehran, Iran.
* To whom correspondence should be addressed.
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Abstract |
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In the present study, effects of intracerebroventricular (i.c.v.) injections of
dopaminergic and cholinergic agents on morphine-induced amnesia in morphine-sensitized
mice were investigated by using a one-trial passive avoidance task. Amnesia induced by
pre-training morphine was significantly reversed in morphine-sensitized mice, which had
previously received once daily injections of morphine (20 and 30 mg/kg, s.c.) for 3
days. Three daily injections of SKF 38393 (1, 2 and 4 µg/mouse, i.c.v.) or SCH
23390 (0.25, 0.5, 0.75 and 1 µg/mouse, i.c.v.) before morphine, and during
morphine-sensitization, decreased and increased the amnesia induced by pre-training
morphine respectively. Three daily injections of quinpirole (0.3, 1 and 3
µg/mouse, i.c.v.) or sulpiride (0.03, 0.1, 0.3 and 1 µg/mouse, i.c.v.)
before morphine, also decreased and increased the amnesia induced by pre-training
morphine respectively. Morphine-sensitized mice received similar injections of
cholinergic agents. Three daily injections of physostigmine (1, 3 and 5
µg/mouse, i.c.v.) or atropine (1, 4 and 7 µg/mouse, i.c.v.) before
morphine, and during morphine-sensitization, decreased and increased the amnesia induced
by pre-training morphine respectively. Three daily injections of nicotine (0.75, 1 and 2
µg/mouse, i.c.v.) or mecamylamine (1, 3 and 6 µg/mouse, i.c.v.) before
morphine, also decreased and increased the amnesia induced by pre-training morphine
respectively. The results suggest that morphine sensitization affects the impairment of
memory formation and thus it is postulated that central dopaminergic and cholinergic
systems may play an important role in this effect.
Key Words:
morphine, dopamine receptor agonists and antagonists, muscarinic and nicotinic receptor agonists and antagonists, sensitization, passive avoidance learning (mice)
