title: L-DOPA attenuates prolactin secretion in response to isolation stress in Holstein steers.
abstract: To clarify endocrine responses to psychological stressors in cattle, the effects of isolation from familiar peers on plasma prolactin (PRL) and cortisol (CORT) concentrations, and the effect of 3,4-dihydroxy-L-phenylalanine (L-DOPA), a precursor of dopamine (DA), on stress-induced PRL secretion were determined in Holstein steers. First, the potency of peripheral L-DOPA administration on attenuation of central DA levels was confirmed. Cerebrospinal fluid (CSF) collected from a chronic cannula in the third ventricle and plasma were sampled 1 h before and 3 h after intravenous injection of L-DOPA (100 mg/head). DA concentrations in CSF increased just after L-DOPA injection with subsequent decrease in PRL secretion. Injection of L-DOPA increased CORT secretion. Second, one experimental steer was isolated in its stall by removing its peers for 2 h with or without- pre-injection of L-DOPA. The concentration of PRL was elevated by isolation treatment, whereas the effect of isolation on CORT concentration could not be detected. The increase in PRL concentration after isolation was abolished by pre-injection of L-DOPA. These results suggest that PRL responds to isolation and that DA neurons in the central nervous system may regulate stress-induced PRL secretion in steers.
authors.affiliation: Animal Physiology Research Unit, National Institute of Agrobiological Sciences.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Kasuya
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yayou
authors.forename: Madoka
authors.initials: M
authors.lastname: Sutoh
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism* / Q000523:psychology*; D004298:Dopamine / Q000134:cerebrospinal fluid; D059290:Dopaminergic Neurons / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D011388:Prolactin / Q000378:metabolism*; D012934:Social Isolation / Q000523:psychology*; D013315:Stress, Psychological / Q000209:etiology* / Q000378:metabolism*
chemical_list: D007980:Levodopa; D011388:Prolactin; D004298:Dopamine; D006854:Hydrocortisone
keywords: cattle; dopamine; isolation; prolactin; stress