Paper Information

Title: 

INTERACTION OF LIGHT DEPRIVATION AND MELATONIN ON LTP INDUCTION IN CA1 AREA OF MALE RAT'S HIPPOCAMPUS

Type: POSTER
Author(s): TALAEI ZAVAREH S.A.R.,DAVARI S.,SALAMI ZAVAREH M.
 
 
 
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: 

Aim: Environmental signals noticeably affect the brain function and development, especially in early life. This study was made to assess effects of dark rearing and the highly synthesized hormone in darkness melatonin on LTP induction of hippocampal responses.
Methods: In vivo experiments were carried out on 2 groups of 45 days old male Wistar rats kept in standard 12 hour light/dark condition (Light Reared-LR) or in complete darkness (Dark Reared-DR) since birth through testing. Each group, in turn, was divided to two, control and melatonin treated groups. Stimulating the Schaffer collaterals of CA3 area of hippocampus field potentials were recorded in the CA1 area. After stability of the responses the hippocampus was perfused by either saline (control) or 2 µg melatonin (drug treated) and recordings continued for more 30 minutes. Then, for induction of LTP, the tetanic stimulation was applied and the field potentials were pooled for 120 minutes post-tetanus.
Results: Tetanic stimulation of the Schaffer collaterals resulted in LTP in both control LR and DR rats, robustly in the former where it lasted for about 90 minutes. Melatonin differently influenced potentiation of the field responses. Whereas melatonin appeared a negligible effect on LTP of the DR treated group it markedly depressed amplitude of post-tetanic responses.
Conclusion: It seems that melatonin deteriorates LTP in the hippocapmal responses, considerably in the LR animals. Weak effect of the drug in the DR rats can be related to insensitivity of melatonin receptors due to increased melatonin serum levels in dark reared rats.

 
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