THE CIRCULATING CONCENTRATIONS OF FSH, LH AND PROLACTIN IN THE ESTRADIOL-IMPLANTED OVARIECTOMIZED EWE TREATED WITH CAFFEINE

Caffeine, a trimethylxanthine alkaloid, is a psyche-active drug that e ffects a wide range of physiological systems, including the reproducti ve system, Reports of infants with intra-uterine growth retardation an d lowered birth weight as a result of in utero exposure to caffeine, a re increasing, The drug is also known to alter steroidogenesis but it is not certain whether this is a direct and/or an indirect effect with the involvement of the central nervous system. Thus, an experiment wa s designed to determine the effect of acute caffeine administration on the circulating concentrations of gonadotrophins and prolactin in the ovariectomized oestradiol-implanted ewe, A single intravenous dose of caffeine (20 mg kg(-1) bodyweight) did not affect circulating gonadot rophin concentrations with the parameters for the pulsatile secretion of luteinizing hormone (LH) and the mean concentration of follicle sti mulating hormone (FSH) being similar in both experimental and control groups, Circulating prolactin levels, on the other hand, were signific antly (P < 0.01) elevated following intravenous treatment with caffein e. The effect was immediate following caffeine administration with ele vated concentrations being maintained over the next 3 h before their r eturn to pre-treatment concentrations. The response was bi-phasic with peaks of prolactin concentrations at 1 and 3 h. The results of this e xperiment show that acute caffeine exposure does not affect the secret ion of gonadotrophins from the anterior pituitary gland, Furthermore, they show that acute administration of caffeine stimulates prolactin s ecretion via an action that is independent of oestradiol feedback and which we suggest, may involve the ACTH/adrenal axis.