Prolactin is associated with the development of photorefractoriness in intact, castrated, and testosterone-implanted starlings
Using radioimmunoassays, prolactin, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured in the plasma of intact, castrated, and testosterone-implanted male starlings. Two groups of birds (intact and castrated males) were transferred when photosensitive from short (8-hr) to long (16-hr) day lengths; in both cases plasma prolactin levels increased steadily reaching a peak after 5 weeks of photostimulation, at the time of the onset of photorefractoriness. Three groups (intacts, castrates, and castrates implanted with Silastic capsules containing testosterone) were exposed to day lengths increasing by 30 min per week from 8 to 16 hr. Again, prolactin levels increased in a similar fashion in all three groups at the time of refractoriness, which occurred when the day length reached 15-16 hr. Thus the timing of photorefractoriness and the associated rise in prolactin secretion which occur in response to photostimulation do not depend upon the presence of the gonads and are not affected when testosterone is maintained at a constant high level. Nor is the increase in prolactin altered when the cycle of gonadotrophin secretion which normally precedes it is completely suppressed by the implantation of a testosterone capsule. It would seem that prolactin secretion in the starling is stimulated by transfer from short to long day lengths, but not as a consequence of high gonadotrophin or androgen secretion rates.
- Research Organization:
- Univ. of Bristol, United Kingdom
- OSTI ID:
- 6472084
- Journal Information:
- Gen. Comp. Endocrinol.; (United States), Vol. 54:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BIRDS
PHOTOSENSITIVITY
FSH
RADIOIMMUNOASSAY
LH
LTH
TESTOSTERONE
BIOLOGICAL EFFECTS
BLOOD PLASMA
CASTRATION
IODINE ISOTOPES
PHOTOPERIOD
ANDROGENS
ANDROSTANES
ANIMALS
BIOLOGICAL MATERIALS
BLOOD
BODY FLUIDS
GONADOTROPINS
HORMONES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KETONES
MATERIALS
MEDICINE
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOASSAY
SENSITIVITY
STEROID HORMONES
STEROIDS
SURGERY
TRACER TECHNIQUES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
551001 - Physiological Systems- Tracer Techniques