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Paper Information

Title: 

EFFECTS OF ATROPINE MICROINJECTIONS INTO THE VENTRAL TEGMENTAL AREA ON MORPHINE-STATE DEPENDENT LEARNING

Type: POSTER
Author(s): DARBANDI N.,REZAYOF A.,ZARINDAST M.R.
 
 
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2007Volume 18
 
 
Abstract: 

Introduction: It is suggested that effects of morphine on learning is mediated by its reward effects in mesocorticolimbic pathway .In the present study, the effects of intra-ventral tegmental area (VTA) injections of muscarinic receptor antagonist, atropine on memory retention and morphine-state dependent learning has been investigated in rats.
Methods:A single-trial step-through passive avoidance task was used for the assessment of memory retention in adult male Wistar rats. In these experiments, animals weighting 220-250 g at the time of surgery were used. Animals were bilaterally cannulated in the ventral tegmental area by stereotaxic instrument, and were allowed to recover 1-week before behavioral testing. Eight animals were used in each group of experiments.
Results: Post-training subcutaneous (s.c.) administration of different doses of morphine (0.5, 1, 3 and 5 mg/kg) dose dependently decreased the learning of a one-trial passive avoidance task and induced amnesia. Pre-test administration of morphine (5 mg/kg, s.c.) induced state-dependent learning acquired under pre-training morphine influence. Pre-test intra-VTA administration of the muscarinic cholinergic receptor antagonist, atropine (1, 2 and 3 µg/rat) alone didnot affect memory retention. While, pretest intra-VTA injection of atropine (1, 2 and 3 µg/rat) 5 min before the administration of morphine (5 mg/kg) dose dependently inhibited morphine state-dependent learning.
Conclusion: The present data show that memory and the processes of learning in animals can be affected by morphine and that morphine produces state-dependent learning. Moreover, it can be concluded that the muscarinic cholinergic receptors in the VTA are involved in mediating morphine state-dependent learning.

 
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