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  • Title: Differential action of somatostatin on peptide-induced release of acetylcholine.
    Author: Kowal V, Wiley JW, Owyang C.
    Journal: Am J Physiol; 1989 Aug; 257(2 Pt 1):G221-5. PubMed ID: 2475031.
    Abstract:
    In this study we examine the mechanism by which somatostatin (SRIF-14) inhibits cholecystokinin octapeptide- (CCK-8) but not substance P-mediated release of [3H]acetylcholine (ACh) from the guinea pig ileum. 2',5'-Dideoxyadenosine, an inhibitor of adenylate cyclase, antagonized the action of CCK-8 and forskolin but had no effect on substance-P-evoked release of [3H]ACh. Addition of theophylline enhanced the release of [3H]ACh stimulated by CCK-8 but not by substance P. These observations suggest that CCK-8, but not substance P, can stimulate cholinergic transmission via an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent pathway. Somatostatin inhibited release of [3H]ACh evoked by CCK-8 and forskolin in a dose-related manner. CCK-8- and forskolin- but not substance P-evoked release of [3H]ACh were maximally inhibited in the presence of 10(-6) M somatostatin (49 +/- 5 and 48 +/- 7% of control, respectively). Pretreatment with pertussis toxin (inactivates inhibitory guanine nucleotide binding proteins) reversed the inhibitory effect of somatostatin on the release of [3H]ACh evoked by CCK-8. These observations suggest that CCK-8 but not substance P can stimulate [3H]ACh by a cAMP-dependent pathway. Somatostatin appears to inhibit the cAMP-dependent component of CCK-8-mediated cholinergic transmission via activation of a pertussis toxin-sensitive G protein.
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