EFFECT OF CONSTANT LIGHT ON RHYTHMIC GASTRIC FUNCTIONS IN FASTING RATS

The effects of four weeks of continuous illumination (LL), a subacute stress, on gastric mucosal endogenous aggressive and defensive factors were studied Young male Sprague-Dawley rats were used with two differ ent illumination regimens: LL and 12 hr light/12 hr dark (LD). At the end of three to four weeks of either regimen of illumination, gastric acid secretion, pepsin secretion, mucus secretion, and potential diffe rence (PD) were studied. All gastric parameters, except mucus secretio n, were significantly reduced by LL. The reduction in acid secretion ( 13.3%) was not significant after Bonferroni correction for the four t tests Pepsin secretion and PD were 27.9% and 24.6% less, respectively. These differences were significant after Bonferroni correction. The L D rats showed significant circadian rhythms for acid mucus, and pepsin secretion. The LL rats showed significant rhythmicity for these same parameters with period lengths different from 24 hr. Gross inspection of the gastric mucosa indicated that 69.8% of the LL rats had lesion s cores of 1.0 or higher, while none of the LD rats had scores above 0.5 .