{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T14:25:23Z","timestamp":1783607123479,"version":"3.55.0"},"reference-count":0,"publisher":"Bioscientifica","issue":"1","content-domain":{"domain":["journals.bioscientifica.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1991,4,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>This study was conducted to determine whether photoperiod-induced changes in serum concentrations of prolactin in cattle were associated with changes in activity of dopamine or 5-hydroxytryptamine (5-HT) neurones in the infundibulum\/pituitary stalk and the secretion rate and number of lactotrophs in the anterior pituitary gland.<\/jats:p>\n                  <jats:p>Sixteen prepubertal bull calves (approximately 8 weeks of age) were divided into two groups. One group of eight was maintained on a photoperiod of 8 h light : 16 h darkness (8L : 16D) and the other group was exposed to 16L : 8D for 4 weeks. At this time calves were injected with a decarboxylase inhibitor (m-hydroxybenzylhydrazine dihydrochloride, NSD 1015) which blocks the conversion of dihydroxyphenylalanine (DOPA) to dopamine and of 5-hydroxytryptophan (5-HTP) to 5-HT. Calves were killed with pentobarbital 15 min later. Accumulations of DOPA and 5-HTP in selected brain regions were used as indices of activity of dopamine and 5-HT neurones respectively. Secretory rate and number of prolactinsecreting lactotrophs were determined by reverse haemolytic plaque assay.<\/jats:p>\n                  <jats:p>Relative to calves exposed to 8L : 16D, exposure to 16L : 8D increased serum concentrations of prolactin by eightfold, anterior pituitary gland weight by 23%, release of prolactin from pituitary explants by 57% and the area of the plaque for prolactin-secreting lactotrophs by 70%. There was no difference in the rates of accumulation of DOPA and 5-HTP in the infundibulum\/pituitary stalk of animals exposed to 4 weeks of 16L : 8D or 8L : 16D.<\/jats:p>\n                  <jats:p>It was concluded that increased serum concentrations of prolactin in bulls exposed to a photoperiod of 16L : 8D for 4 weeks were associated with increased secretion of prolactin from lactotrophs which was not the result of a coincident reduction in activity of dopamine neurones or an activation of 5-HT neurones that terminate in the infundibulum\/pituitary stalk.<\/jats:p>\n                  <jats:p>Journal of Endocrinology (1991) 129, 141\u2013148<\/jats:p>","DOI":"10.1677\/joe.0.1290141","type":"journal-article","created":{"date-parts":[[2008,12,11]],"date-time":"2008-12-11T18:11:20Z","timestamp":1229019080000},"page":"141-148","update-policy":"https:\/\/doi.org\/10.1530\/crossmarkpolicy-5","source":"Crossref","is-referenced-by-count":3,"title":["Effects of photoperiod on lactotrophs and on dopaminergic and 5-hydroxytryptaminergic neurones in bull calves"],"prefix":"10.1530","volume":"129","author":[{"given":"S. A.","family":"Zinn","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"L. T.","family":"Chapin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"K. J.","family":"Lookingland","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"K. E.","family":"Moore","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"H. A.","family":"Tucker","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"416","container-title":["Journal of Endocrinology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/joe.bioscientifica.com\/view\/journals\/joe\/129\/1\/joe_129_1_019.xml","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article-pdf\/129\/1\/141\/100251\/joe_129_1_019.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article-pdf\/129\/1\/141\/100251\/joe_129_1_019.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T14:11:52Z","timestamp":1783606312000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.bioscientifica.com\/joe\/article\/129\/1\/141\/17053\/Effects-of-photoperiod-on-lactotrophs-and-on"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1991,4,1]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1991,4,1]]}},"URL":"https:\/\/doi.org\/10.1677\/joe.0.1290141","relation":{},"ISSN":["1479-6805","0022-0795"],"issn-type":[{"value":"1479-6805","type":"electronic"},{"value":"0022-0795","type":"print"}],"subject":[],"published":{"date-parts":[[1991,4,1]]}}}