['The purpose of this study was to investigate the effect of endogenous mast cell degranulation on the contractility of isolated cervical strips from nonpregnant and pregnant guinea pigs.', 'Longitudinal cervical strips from nonpregnant and pregnant (mid and term) guinea pigs were used for isometric tension recording. Responses to the mast cell degranulating agent, compound 48/80, were compared in the absence or presence of different inhibitors and receptor antagonists. Concentration-response curves were obtained to histamine and 5-hydroxytryptamine in strips that were incubated with antagonists or solvent.', 'Compound 48/80 and histamine significantly increased contractility of cervical strips in all 3 groups of animals. The inhibitor of mast cell degranulation significantly reduced responses to compound 48/80 and histamine-1 receptor antagonist reduced responses to histamine in all 3 groups. Histamine-1 receptor antagonist significantly inhibited responses to compound 48/80 in nonpregnant and mid pregnant guinea pigs. Histamine-2 receptor antagonist did not alter responses to compound 48/80 nor to histamine. The receptor antagonist 5-hydroxytryptamine-2 significantly inhibited cervical contractility that was induced by compound 48/80 in tissues from mid pregnant and term pregnant guinea pigs. Lipoxygenase inhibitor was effective in mid pregnant guinea pigs. Cyclooxygenase inhibitor, 5-hydroxytryptamine, and a combination of lipoxygenase and cyclooxygenase inhibitors had no effect on cervical contractility.'] Does endogenous mast cell degranulation modulate cervical contractility in the guinea pig?