Serotonin levels in the hen ovarian follicles after methallibure (I.C.I 33, 828) treatment.

The purpose of the present study was to examine the effect of methallibure (MLB), a non-steroid inhibitor of pituitary gonadotrophic activity on serotonin (5-HT) levels in the wall of preovulatory follicles (F1-F4) in the domestic hen. 5-HT was determined spectrofluorometrically. Hens were treated with MLB (10 mg/hen per os) twice a day for 3 successive days. 5-HT was determined in F1-F4 (F1 greater than F2 greater than F3 greater than F4) follicles of the control group, on the next day (MLB-1 group) and 6 days following cessation of MLB administration (MLB-6 group). During MLB treatment egg production was inhibited in all hens. In the MLB-6 group, five hens out of seven took up egg laying on the sixth day after MLB administration. Within each examined group there were no significant differences in 5-HT concentration between F1-F4 follicles. In comparison to the control, MLB caused a significant (P less than 0.01-0.05) increase of 5-HT concentration in F1 (MLB-1 group) and F4 (both MLB-groups). The results obtained indicate that there is a relationship between pituitary activity and 5-HT levels in the preovulatory follicles of the domestic hen.