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Surgical disconnection of the ovine hypothalamus from the pituitary gland (hypothalamo-pituitary disconnection; HPD) has provided a useful experimental model for studying the control of gonadotrophin secretion. The objective of the present study was to define the characteristics of prolactin secretion using stimuli acting through the hypothalamus or directly on the pituitary gland in HPD ewes. Prolactin responses to either a stressful stimulus or the dopaminergic antagonists metoclopramide (20 mg i.v.) or chlorpromazine (50 mg i.v.) seen in intact animals (sham-HPD) were completely abolished by HPD. Injection of TRH (100 micrograms i.v.) caused an immediate release of prolactin in both groups of ewes. In the HPD ewes plasma prolactin concentrations remained raised for at least 3 h after TRH injection, whereas in sham-HPD ewes prolactin concentrations began to decline after 20 min. Administration of bromocriptine (1 mg i.v.) 10 min after TRH inhibited the prolonged response to TRH in HPD ewes. The results support the hypothesis that prolactin exerts a short-loop feedback effect on its own secretion at the hypothalamic level.
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
January 1995,
Andrologia,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
October 1982,
Archives of disease in childhood,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
June 1974,
The Journal of endocrinology,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
November 1975,
South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
November 1971,
The Journal of endocrinology,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
December 1974,
Annals of internal medicine,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
July 1975,
Clinical endocrinology,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
July 1971,
Lancet (London, England),
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
July 1980,
Postgraduate medical journal,
G B Thomas, and
J T Cummins, and
J M Hammond, and
R J Horton, and
I J Clarke
April 1972,
Lancet (London, England),
