Studies on the contractility of follicular wall with special reference to the mechanism of ovulation in hens.

To investigate the mechanism of ovulation in the hen, histological and physiological investigations on the contractility of the follicular wall were carried out. Smooth muscle bundles in the loose connective tissue coat from the stalk to the equator showed spontaneous rhythmic contractions with an alternation of contraction and pausing periods of about 4 min. The administration of prostaglandins F2 alpha (PGF2 alpha), E2 (PGE2), ovarian oviposition inducing factor (OOIF), oxytocin and acetylcholine increased the frequency and amplitude of the contractions. The theca layer showed spontaneous contractions at a frequency of about 30 per 10 min. PGF2 alpha, OOIF, acetylcholine, adrenaline and noradrenaline induced tonic contractions, whereas PGE2, oxytocin and histamine induced relaxation. It is suggested that the contraction of the follicular wall promotes the rupture of the stigma at ovulation and the neurotransmitters as well as prostaglandins and OOIF may be involved in this event.