Alterations of Amylase Secretion in the Chronically Reserpinized Rat

Alterations of the Pancreatic Secretory Responses to Secretin and to the lonophore A23187 by Reserpine: A Calcium-Mediated Phenomenon?

“…Indeed, as indicated in table 6, comparisons of secretory dose-response curves to carba mylcholine, to caerulein and to the phorbol ester TPA fol lowing pancreatic acini pre-exposure to a supramaximal concentration of carbamylcholine [8] or reserpine treat ment [7] indicate identical modifications. Also presented in table 6, the present study reveals that the secretory response to secretin is significantly reduced after reser pine treatment as it was after pre-exposure to a high con centration of carbamylcholine [9].…”

“…The morphologi cal secretory alterations observed in these glands resemble those of cystic fibrosis [1,5,6]. In a recent study [7], we have shown that in vivo reser pine caused desensitization of the pancreatic acini secre tory response to carbamylcholine while the secretory responses to caerulein, a cholecystokinin analogue, and to the phorbol ester 12.0-tetradecanoyl phorbol-13 acetate …”

“….0 ml kg^1 of the vehicle used to dissolve the reserpine drug; (2) con trol (C), 1.0 ml kg-1 of the vehicle; and (3) reserpine-treated rats (R), 1 mg kg-1 of reserpine. C and R rats were fed powdered rat chow ad libitum; PF rats were restricted to the amount of powdered food con sumed daily by the R rats; the amount of food given daily to these PF rats was previously reported [7], In a second set of experiments, C and R rats were treated as described above, but each group was sub divided and received for 7 days atropine sulfate at 50 mg kg"1 twice daily intraperitoneally.…”

“…To test the hypothesis that reserpine may have caused desensitization of amylase release by increasing endoge nous acetylcholine release from nerve terminals [7], the reserpine treatment was given in association with atro pine to neutralize any potential endogenous release of ace tylcholine by reserpine. As shown in table 5, although atropine slightly interfered with the secretin secretory responses at secretin concentrations below IO-8 M in the C group, the reduced response to secretin observed in the R group was not at all modified by the atropine treat ment.…”

“…Short-term exposure of pancreatic acini to carbamylcholine, a muscarinic agonist, reduced the subsequent stimulation of amylase release caused by this same agonist and induced secretin subsensitivity without altering the subsequent secretory responses to TPA, to caerulein and to the ionophore A23187 [8,9], Because of the remark able similarity existing between secretory responses of pancreatic acini to secretagogues following in vivo reser pine treatment and desensitization of the pancreatic aci nar cell by a cholinergic muscarinic agonist, this study was undertaken to (1) characterize the alterations caused by reserpine on the secretory responses of the pancreatic acini to secretin and to the ionophore A23187 and (2) to substantiate the hypothesis that reserpine alters pancreat ic secretory responses to secretagogues through the release of endogenous acetylcholine [7], Since reserpine has been shown to reduce food consumption in rats [10], the secre tory response of pair-fed (PF) animals to reserpine was also examined to distinguish between a true reserpine effect and that of reduced food intake.…”