The hypothalamic areas involved in the control of mammotrophic and lactotrophic processes in sheep
Domański, E.; Polkowska, J.
Endocrinologia Experimentalis 7(3): 229-246
1973
ISSN/ISBN: 0013-7200 PMID: 4356253 Document Number: 66222
Electrolytic lesions were placed in various hypothalamic areas of lactating and pregnant Merino sheep. Lesions in the anterior median eminence of lactating ewes decreased their milk yield, but this was restored by replacement therapy with prolactin + growth hormone (GH) + ACTH but not by prolactin alone. Similar lesions during late pregnancy inhibited mammary gland development and degranulation of pituitary lactotrophic cells; these animals delivered at full term but subsequent milk yield was low (30-100 ml/day). Replacement therapy (prolactin + GH + ACTH + thyroid hormone) promoted mammary growth and lactation only if given before parturition. Lesions located in the posterior median eminence (caudal infundibular nuclei) during pregnancy resulted in precocious mammary development and pronounced degranulation of lactotrophs, and milk yields at subsequent lactation were normal or slightly depressed. Lesions in the anterior, medial, basal hypothalamus during pregnancy inhibited mammary growth. Replacement therapy (prolactin + GH + ACTH) during lactation did not promote mammary growth but increased milk yield by an amount which depended on state of development of mammary gland. In well-developed glands, replacement with ACTH alone initiated lactogenesis and restored milk production. Results support the view that hypothalamic control of pituitary mammogenic and lactogenic processes involves stimulatory and inhibitory factors.