PGF_2α-induced milk ejection in ewes having cyclic or pregnant corpora lutea

Abstract

Summary. The (fig. 4).After D15, the increase in intramammary pressure progressively weakened and became 0 at D17 in the cyclic ewes, whereas in the pregnant animals there was a renewed increase in intramammary pressure until D20 ; this regressed progressively afterwards and disappeared towards D45. This transitory, renewed activity between D1 5 and D20 might be an indirect or direct result of the message delivered by the embryo to maintain the corpus luteum. Several hypotheses are discussed with a view to explaining this phenomenon.Introduction.

Suppression par la lutectomie de l'accroissement simultané de la pression intramammaire et de l'ocytocinémie, induit par l'injection de PGF2α, chez la brebis

“…Ce travail prouve que l'éjection du lait observée après l'administration intraveineuse de PGF 2a (Labussière et al, 1983(Labussière et al, , 1986(Labussière et al, , 1988a (Labussière et al, 1988) après le 1 Séjour de gravidité est principalement permise par la reconstitution des stocks lutéaux d'ocytocine (Sheldrick et Flint, 1981Flint, a, 1983, même si la synthèse de cette hormone par le corps jaune devient alors faible (Harrisson et al, 1987 …”

“…Dans ce groupe, la diminution progressive des réponses et leur disparition vers la fin du 2 e mois de gravidité est en effet comparable à ce qui a été précé-demment observé chez des brebis gestantes de la même race (Labussière et al, 1988a).…”

Intramammary pressure and luteal oxytocin after PGF2α administration in cycling and early pregnant ewes

“…Basal pressures were compensated for and pressure variations were recorded with Hewlett-Packard recorder (type 7754 A) equipped with a 8805 B amplifier. The surface area under the curve and the mean amplitude were measured during the first 4 min after PGF2a challenge as previously described (Labussiere et al 1988a).…”