Alteration of the rat exocrine pancreas after chronic scopolamine administration

Life with the pancreas: A personal experience

This review article has primary objective to summarize pancreatic research which has been done in our laboratory since 1965, the first year of the author's registration in the Ph.D. program at the University of Sherbrooke (Canada). It covers the following major topics of pancreatic physiology: controls of pancreatic adaptation to diet, control of pancreatic enzyme secretion, control of pancreatic enzyme synthesis, control of pancreatic growth, intracellular events stimulated during pancreatic growth, pancreas regeneration after pancreatitis and pancreatectomy, the pancreatic cholecystokinin receptor types 1 and 2, growth control and cell signaling in pancreatic cancer cells and finally, cystic fibrosis.

Pharmacological analysis of diisopropyl fluorophosphate: effects on core temperature, heart rate, and motor activity in the unrestrained rat

Humans acutely exposed to anticholinesterase (anti-ChE) pesticides often become febrile, whereas rats and other rodents become markedly hypothermic. The rat may nonetheless be a useful model for anti-ChE toxicity because recent work using radiotelemetry demonstrated an elevation in core temperature of unrestrained rats for several days following acute exposure to the anti-ChE, diisopropyl fluorophosphate (DFP). To discern the mechanisms of DFP-induced hypothermia and hyperthermia, various pharmacological agents were administered acutely or chronically to rats injected with 1.5 mg/kg DFP (SC). Core temperature, heart rate, and motor activity were monitored continuously via radiotelemetry. Methylscopolamine, a peripheral muscarinic antagonist, attenuated the DFP-induced hypothermia by 1.0 degree C and reversed the DFP-induced bradycardia. Chronic scopolamine, a central and peripheral muscarinic antagonist, delivered via a subcutaneously implanted minipump (9.5 mg/kg/day) blocked DFP-induced hypothermia and hyperthermia. Propranolol (10 mg/kg; SC), a general beta blocker, augmented the bradycardic effects of DFP but had no effect on body temperature. Sodium salicylate (200 and 300 mg/kg; IP), an antipyretic that inhibits prostaglandin synthesis, administered during the period of DFP-induced hyperthermia produced a transient recovery in body temperature. Overall, DFP-induced hypothermia and hyperthermia in the rat appear to be mediated via cholinergic activation in the CNS because both are blocked by scopolamine. The decrease in core temperature following sodium salicylate suggests that prostaglandin release is involved in the manifestation of DFP-induced hyperthermia. The elevation in core temperature after DFP appears to involve neurochemical pathways similar to that of fever.

Toxicity study of the main alkaloids of Datura ferox in broilers

Seeds of the weed Datura ferox are frequent contaminants of raw materials used for animal feed. These seeds produce various toxic effects and contain mainly the alkaloids scopolamine and hyoscyamine. In this 3-month toxicity study, a mixture of scopolamine and hyoscyamine (98:2) was incorporated at four total alkaloid levels (1.5, 15, 75 or 150 mg/kg feed) into a control diet fed to 100 broilers. Alkaloid feeding caused significant reductions in the body weight gain of birds, especially of those fed a dose of 150 mg alkaloid/kg feed. Growth-retarding effects, however, were transient, as no changes in body weight gain were noted after 52 days of alkaloid feeding. Alkaloid-treated broilers showed no significant differences from controls with respect to the cardiac rate and breathing frequency nor in relation to plasma aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase activities. In contrast, plasma leucine aminopeptidase activity was significantly reduced after 3 months in all alkaloid-fed birds. Autopsy and histological examination of tissues by light and electron microscopy revealed no pathological changes associated with alkaloid feeding. Broilers appeared generally healthy and behaved normally throughout. These data should be considered in the formulation of new, improved regulations defining the maximum allowable alkaloid content of D. ferox seeds contaminating raw materials destined for use as broiler feed.

Toxicological evaluation of jimson weed (Datura stramonium) seed

Diets containing 0.5, 1.58 and 5.0% jimson weed seed were fed to male and female rats (20/group) in a 90-day subchronic feeding study. The alkaloid content was 2.71 mg atropine and 0.66 mg scopolamine/g of seed. Gross clinical observations, body weights and feed and water intakes were recorded weekly. Tear production and pupil dilation measurements were made throughout the study. At 90 days, all of the animals were autopsied and clinical-chemistry analyses, complete haematology and bone-marrow evaluation for evidence of clastogenic effects were performed. Tissues from control (0% seed) and high-dose animals were examined histologically. The principal effects of jimson weed seed were: decreased body-weight gain, serum albumin and serum calcium; increased liver and testes weights (as a percentage of body weight), serum alkaline phosphatase and blood urea nitrogen. Female rats showed more marked responses to jimson weed seed than did males. In addition to the effects seen in both sexes, the females developed decreased serum total protein and cholesterol, and increased serum glutamic-pyruvic transaminase and chloride, red blood cell count, haemoglobin concentration and packed red cell volume. No histological lesions were associated with ingestion of jimson weed seed at 5.0%. It is concluded that jimson weed seed at concentrations of 0.5% or more in the diet produced adverse physiological changes in rats.

Contraindication for osmotic mini-pump in the abdominal cavity to study muscarinic cholinergic control of pancreatic enzyme secretion and muscarinic receptors

Alzet mini-pumps were used to study modulation of rat pancreatic muscarinic receptors and the acinic secretory response to long-term N-methylscopolamine (NMS) treatment. Infused intraperitoneally (i.p.), NMS, 25 mg.kg-1.day-1 for 14 days, resulted in a shift to the left in the amylase dose-response curve to carbamylcholine (Cch) and an increase in receptor concentration compared to saline-infused group. Compared to previously published control data [4,5] the saline-infused group exhibited desensitization with increased EC50 for secretion. An alternative mode of saline treatment, subcutaneous (s.c.) infusion showed normal pancreatic secretory response. Desensitization by i.p. saline infusion was prevented by NMS infusion. In conclusion, a foreign body such as a mini-pump in the abdominal cavity can cause desensitization of the pancreatic secretory function under neural cholinergic control.