Paper Information

Title: 

EFFECT OF CHRONIC ADMINISTRATION OF ULTRA LOW DOSES OF MORPHINE ON LEARNING PROCESSES AND SPATIAL MEMORY RETENTION IN MORRIS WATER MAZE IN RAT

Type: POSTER
Author(s): KAVOUSI Z.*,FEREYDOUNI MASOUD,MOGHIMI ALI,SADEGH AZAM
 
 *DEPARTMENT OF BIOLOGY, FACULTY OF SCIENCE, FERDOWSI UNIVERSITY OF MASHHAD, MASHHAD, IRAN
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2009Volume 19
 
 
Abstract: 

The hippocampus involves in learning and memory. The opioid receptors have reported in hippocampus. Effects of morphine on the neuronal and cognitive processes have suggested and paradoxical results have obtained. Study of the effect of chronic administration of ultra low to usual doses of morphine on learning processes and memory retention is the aim of this research.
Adult male wistar rats (200-250g) were divided into 4 groups (n=7): sham-control (saline), chronic morphine at ultra low doses (1μg/kg, 100μg/kg) and usual dose (10mg/kg). Memory was assessed by the Morris water maze test. Animals were trained for 4 days and four successive trials. Morphine was injected intraperitoneally (i.p.) half hour before start of trainings. The latency and distance to reach the hidden platform was recorded. On the 5th day, animals were allowed to swim 60s in the absence of platform without morphine administration, and the time spent in target quadrant was recorded.
Difference between sham-control and chronic morphine (1 and 100μg/kg) groups on learning processes was not significant. Chronic administration of morphine (10mg/kg) significantly impaired learning. In addition, on 5th day, that memory retention test was done, a significant difference was not found.
Variety of morphine doses effects, probably caused by variety of function of opioidergic system. Some reports have been shown that chronic treatment of morphine reduces the hippocampal ltp. So maybe morphine has induced learning impairment related to its inhibitory effect on cholinergic functions in hippocampus area or physical synaptic changes.

 
Keyword(s): LEARNING, MEMORY RETENTION, ULTRA LOW DOSES OF MORPHINE, MORRIS WATER MAZE
 
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