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The objective of this study was to determine the role of cyclosporin A (CsA) on cold-restraint-induced gastric lesions. Animals were subjected to 3 h immobilization at 4 degrees C in plastic restraining devices following a starvation period of 48 h. Gastric samples were obtained for the measurement of myeloperoxidase (MPO) activity, an index of number of peroxidase positive cells and thiobarbituric acid-reactive substances (TBARS; lipid peroxidation). Animals were pretreated with CsA which is a potent immunosuppressant and inhibits ischemia/reperfusion-induced polymorphonuclear leukocyte (PMN) infiltration. Cold-restraint administration significantly elevated the tissue MPO activity and TBARS formation. CsA pretreatment significantly reduced the severity of cold-restraint-induced gastric lesions while attenuating the elevated MPO measurements observed during cold-restraint administration. Animals rendered neutropenic with antineutrophil serum (ANS) exhibited significantly less gastric mucosal injury normally observed after cold-restraint stress. Neither CsA nor ANS treatment effected the elevated TBAR levels, indicating that PMNs are not involved in the lipid peroxidation process observed after cold-restraint stress. In conclusion, the results of this study indicate that CsA is capable of inhibiting cold-restraint-induced gastric mucosal injury and can attenuate the cold-restraint-induced increases in gastric MPO measurements. Our results also indicate that PMNs may be the important mediators of cold-restraint-induced gastric lesions.

Central cardiovascular effects of cholinergic agonists depend on the dose, site and mode of administration, species, and to the state of the animal. Intravenous injection of physostigmine and intracerebroventricular injection of carbachol produced pressor and tachycardic responses in urethane-anesthetized rats. Both agents also elicited pressor responses in conscious rats, but bradycardia occurred in the presence of anesthesia. Additionally, pressor responses to physostigmine, but not to carbachol, were significantly exaggerated by urethane anesthesia. These results demonstrate that anesthesia depresses cardiovascular reflexes and the inhibitory control mechanisms on acetylcholine release from the nerve endings involved in cardiovascular regulation. The role of the central nucleus of the amygdala (CNA) was also investigated in this study. The pressor effects of intracerebroventricular injection of carbachol were significantly attenuated by electrolytic ablation of the CNA, but heart rate changes were not altered both in anesthetized and conscious rats. These results indicate that the CNA plays a role in cholinergic control of blood pressure, but not in the regulation of heart rate.

1. The aim of the present study was to determine the role of 5-HT3 receptors of the gastroprotective effect of salmon calcitonin (sCT) and sCT-induced changes in gastric, hepatic, brain and brainstem glutathione (GSH) and lipid-peroxidation (LP) levels in rats subjected to cold-immobilization stress. 2. Stress exposure resulted in ulcer formation and a decrease in GSH levels of the liver, brain and brainstem and an increase in gastric and hepatic LP (P < 0.05). 3. sCT prevented stress-induced gastric ulcer development (P < 0.01) and reversed the decrease in hepatic and brain GSH levels (P < 0.05). 4. In the present study, a 5-HT3 receptor antagonist, ICS 205,930 was used. Interestingly, the effect of the blocker on GSH and LP levels of the tissues studied was similar to those of sCT. 5. ICS 205,930 dose dependently reversed the anti-ulcer effect of sCT although it did not antagonize the effect of sCT on GSH and LP levels, but it seemed to show an additive interaction for brain and brainstem GSH and gastric LP levels with sCT.

The gastric emptying of liquid test meals is dependent on resistance to flow at the pylorus and on pressure gradients between the duodenum and the body of the stomach. In the present study, we investigated the role and subtypes of muscarinic receptors during gastric emptying of various liquid test meals in conscious rats with gastric fistula after Roux-en-Y antrectomy. In the control rats with gastric fistula but with intact reflex pathways and pylorus, the non-selective muscarinic antagonist atropine (7 mg/kg i.p.) and M1-selective pirenzepine (7 mg/kg i.p.), acting possibly on M1 receptors, delayed saline emptying by suppressing cholinergic tone and thus relaxing the body of the stomach and contracting the pyloric sphincter. On the other hand, in Roux-rats saline and hyperosmolal saline emptying were not significantly affected, while the inhibitory effect of HCl was completely reversed. Furthermore, peptone-induced delay of gastric emptying in control rats was also reduced in Roux-rats. Pirenzepine abolished the facilitating effects of Roux-en-Y operation on acid and peptone emptying and M2-selective antagonist AF DX-116 (7 mg/kg i.p.) did not have any inhibitory effect in this regard. In conclusion, Roux-en-Y gastrectomy without vagotomy does not slow gastric emptying of liquids, and it reverses the inhibitory effects of peptone and acid through an atropine- and pirenzepine-sensitive pathway.