Senna still causes laxation in rats maintained on a diet deficient in essential fatty acids

The laxative effect of senna has been investigated in normal and essential fatty acid deficient (EFAD) rats. Oral administration of senna pod extract (7-5-90 mg kg-1) produced a dose-dependent increase in the number of soft faeces excreted by normal rats. Senna 30 mg kg-1 also reversed net absorption of water and increased the prostaglandin (PG) production in the colonic lumen of normal rats by about four times. Oral administration of senna pod extract to rats, maintained on a fat-free diet for 30-90 days, produced diarrhoea and reversed net absorption of water as in normal rats. However, a fat-free diet reduced the PG production drastically in the colonic lumen both in senna-free rats and in senna-treated rats. In EFAD rats carrageenan oedema, but not dextran oedema, was also drastically reduced. Since PG mediation is not present in EFAD rats we conclude that the PG are not essential for laxation induced by senna and that water secretion and PG production in the rat intestinal lumen are unrelated.