Effects of short-term hyper- and hypoprolactinaemia on hormones of the pituitary, gonad and -thyroid axis and on semen quality in male Beagles.
Effects of a short-term hyper- and hypoprolactinaemia on serum concentrations of LH, testosterone and semen quality in six male Beagles were investigated. Blood samples were collected at 3-day intervals for 12 weeks. The time span was divided into five 3-week periods: pre-treatment, metoclopramide (MCP) treatment (0.2 mg/kg orally three times daily), cabergoline (CAB) treatment (5 microg/kg orally once daily), post-treatment 1 and post-treatment 2. In the latter, only semen characteristics were evaluated. Semen parameters were analyzed once per week during the whole 15-week investigation time. At the end of each period, the effects of a single intravenous injection of thyrotropin-releasing hormone (TRH; 10 microg/kg) on the secretion of prolactin (PRL), LH, testosterone, thyroid-stimulating hormone and thyroxine (T4) were investigated. Pre-treatment serum PRL concentration increased under MCP (p < 0.05), followed by a decrease under CAB administration (p < 0.05). Luteinizing hormone and testosterone concentrations were not affected. Except for straight-line sperm velocity, semen quality did not differ between collection periods. A single iv TRH injection induced a significant PRL increase at 20 min in all experimental periods except during CAB treatment. Luteinizing hormone and testosterone did not show clear TRH-related changes. Basic T4 levels were significantly reduced after CAB treatment (p < 0.05). The results of the present study demonstrate that MCP-induced short-term hyperprolactinaemia in male beagles does not seriously affect the hypothalamo-pituitary axis and semen quality.
Koivisto
M B
MB
Department of Clinic, Surgery and Animal Reproduction, Veterinary Medicine, São Paulo State University, São Paulo, Brazil. koivisto@fmva.unesp.br
Eschricht
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F
Urhausen
C
C
Hoppen
H O
HO
Beyerbach
M
M
Oei
C H Y
CH
Günzel-Apel
A R
AR
D000818:Animals; D000077465:Cabergoline; D004285:Dogs; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004873:Ergolines / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects*; D011388:Prolactin / Q000097:blood*; D012661:Semen / Q000187:drug effects*; D013737:Testis / Q000187:drug effects*; D013739:Testosterone / Q000097:blood; D013961:Thyroid Gland / Q000187:drug effects*; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology; D013974:Thyroxine / Q000097:blood
D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D004873:Ergolines; D013739:Testosterone; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D013972:Thyrotropin; D008787:Metoclopramide; D000077465:Cabergoline; D013974:Thyroxine