INFLUENCE OF ADENOSINE, CAMP AND DB-CAMP ON RESPONSES OF ISOLATED TERMINAL GUINEA-PIG ILEUM TO ELECTRICAL-STIMULATION

  • 1 January 1976
    • journal article
    • research article
    • Vol. 223  (2) , 187-195
Abstract
Adenosine, cyclic[c]AMP and dibutyryl[db]-cAMP inhibited nerve-mediated contractions of the terminal ileum elicited by electrical stimulation (ES). Responses to ES at 30 Hz, possibly of adrenergic origin, were considerably more affected than the responses to ES at 3 Hz, which may be of purinergic origin. The following order of relative inhibitory protencies was established: adenosine > cAMP > db-cAMP. Adenosine, cAMP and db-cAMP did not affect the contractile responses of the preparation to histamine, K and noradrenaline. The inhibition of nerve-mediated contractions may be due to an action on presynaptic sites, i.e., on the neural network within the intestine. This action was antagonized by an increase in external Ca and by aminophylline, which increases intracellular Ca. The inhibitory action of adenosine, cAMP and db-cAMP seemingly resulted from a reduction of Ca fluxes across the neural membrane and to a subsequent reduction in the release of neurotransmitter(s). The inhibitory effect of cAMP may be nonspecific and was presumably related to adenosine in its molecule.

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