Objectives: 

Stress can induce various physiological and hormonal disturbances concerning feeding. One of the important gastric hormones to control digestion is somatostatin. Here, we investigated in vitro the changes induced by gravity-stress in the effects of somatostatin in the smooth muscles of the ileum, and compared the results obtained in male and female.

Materials: 

Rats(Wistar, SPF, initial BW: about 50g) were divided into Control (1G) and 3G groups. 3G stress (every day for 10 min) was applied by a centrifugal apparatus for 1, 3, 15 and 30 days. At each of these time points, and immediately after coming out of the centrifuge, a 1 cm-long section of the ileum was isolated under barbiturate anesthesia and fixed in a Magnus-type chamber filled with Tyrode solution. Digestive movements were observed for 60 s following application of somatostatin (10-9-10-7 mg/ml).

Results: 

Phasic and tonic patterns were observed in the ileal smooth muscle activities. The former were peristalsis-like movements and the latter presented as slow fluctuations of the baseline. Somatostatin induced irregular rhythm and amplitude of the phasic movements. However, tonic activities (tonus level) were mostly inhibited by somatostatin application. 3G conditioning significantly reversed the somatostatin-induced inhibition of ileum muscles at day 3 in females, but not in males (t-test, p<0.05).

Conclusions: 

The present study showed that gravity-stress changed somatostatin effects on tonic ileal contraction in the female, but not in the male, indicating the occurrence of sex differences in the gastric hormonal changes induced by stress. The fact that tonic contraction level induced by somatostatin application was well antagonized by stress at an early stage (at day 3) in females, suggests that stress enhanced the tonus of the ileal smooth muscles through down-regulation of somatostatin sensitivity.