Alteration by histamine of the sympathetic nerve-mediated contractions in the bovine ovarian follicle wall in vitro

The histaminergic effect on electrically induced contractions and tritium release was studied in vitro, using strips from the wall of mature bovine ovarian follicles. Follicular fluid and blood plasma from the animals were analysed for electrolyte, bicarbonate, glucose and total protein concentrations in order to compare them with the concentrations of these components in the Krebs-Ringer solution used in the experiments. Electrical field stimulation (EFS) of the follicle strip caused a contraction which was completely blocked by tetrodotoxin and was predominantly of adrenergic origin since phentolamine, in contrast to atropine, blocked the response. The neurogenic response was inhibited by histamine in a concentration-dependent way via the H1-receptor since the H1-antagonist, pyrilamine, counteracted the inhibitory effect of histamine while the H2-antagonist, cimetidine, potentiated the effect. This histaminergic response of EFS-induced contractions could be reproduced in experiments where the H1-agonist, 2-methylhistamine, was inhibitory while the H2-agonist, 4-methylhistamine, had no obvious influence on the twitch response. Histamine reduced the contractile response to exogenous noradrenaline via the H1-receptor, because pyrilamine counteracted, and cimetidine potentiated the effect. The histamine-induced depression of the motor response to EFS and exogenous noradrenaline was probably due to a postjunctional effect mediated by the H1-receptor. Experiments utilizing [3H]noradrenaline release during EFS did not suggest prejunctional effects of histamine. Chemical determinations on follicle fluid and plasma showed that the artificial follicular fluid imitated well the environmental conditions the follicle wall is exposed to in situ.