EFFECT
OF MELATONIN ON THE ISOLATED RAT ANOCOCCYGEUS MUSCLE
Bilgen BAŞGUT*o, Feyza DEDEMOĞLU*, Gülden
GÜLSOY*, İclal ÇAKICI**, Nurettin ABACIOĞLU*
* Gazi University, Faculty of Pharmacy, Department of Pharmacology,
06330 Etiler, Ankara - TURKEY. * Yeditepe University, Faculty
of Pharmacy, Department of Pharmacology, 34755, İ çerenköy,
İstanbul - TURKEY
oCorresponding Author
Summary
The aim of the present study was to investigate the effect
of melatonin on the isolated rat anococcygeus muscle (RAM).
The RAM was isolated as described by Gillespie 1971. The
muscles were mounted in an organ bath containing modified
Krebs-Henseleit solution at 37°C and, changes in the
tension due to the precontractile agents and melatonin were
measured by isometric force displacement transducers. Although
cumulative addition of melatonin (10 -10 -10 -3 M) produced
no effect on the basal tone of the anococcygeus muscle,
it caused an inhibitory action on the muscle pre-contracted
by KCl (70 mM) and phenylephrine (1.7x10 -6 M). In the sodium
fluoride (NaF) (3x10 -3 M)-precontracted muscles, melatonin
(10 -5 -10 -3 M)-induced maximum relaxation was found higher
than that obtained in phenylephrine or KCl-precontracted
RAM. Incubation with phorbol myristate acetate (PMA (10
-10 -10 -4 M) an activator of protein kinase C) produced
no effect on the resting or precontracted muscle. In conclusion,
the inhibitory effect of melatonin might be related to the
G-protein mediated pathways, but not to protein kinase C.
Key Words :
Melatonin, phenylephrine, KCl, NaF, rat anococcygeus
muscle.
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