Effects of protein restriction, melatonin administration, and short daylength on brain benzodiazepine receptors in prepubertal male rats
The possibility that there are changes in brain benzodiazepine binding sites controlled by photoperiod was investigated in two strains of male rats. The hypothesis was tested by 3H-diazepam binding studies in various brain regions of prepubertal rats maintained in 14 or 10 h of light or treated with late-afternoon injections of melatonin (50 micrograms/day). Protein restriction was applied during the experiment to sensitize the animals to the treatments. Under the conditions employed, rats kept in short daylength throughout or kept on long photoperiod and given late-afternoon melatonin injections showed evidence of delayed puberty (seminal vesicle, ventral prostate, and testis weight decreased by 45%, 55%, and 60% respectively, compared to control rats). Binding measurements were made 1 h before and 2 and 5 h after the onset of darkness in the pubertal (42-day-old) or experimentally prepubertal rats. In the rats of the Porton strain (for which protein restriction was obligatory for the gonadal response) there was no consistent treatment or time effects on specific binding of 3H-diazepam to washed membranes of the hypothalamus, midbrain, or striatum. Similarly, there were no differences in the stimulation of 3H-diazepam binding by 100 microM GABA or the inhibition of binding by 50 microM N-acetyl 5 methoxy kynurenamine. By contrast, in Wistar rats, specific binding to midbrain membranes was reduced 5 h after dark compared to 2 h (37% saline; 20% melatonin) and the extent of stimulation by GABA in the hypothalamus was increased 5 h after darkness (35.6% to 46.7% saline; 37.4% to 50% melatonin). Melatonin treatment resulted in significantly higher specific binding in the hypothalamus 2 h after dark (10%, control fed; 20%, protein restricted) but reduced the GABA induced stimulation of binding in the midbrain (35.5% to 25%, control fed; 33.7% to 23.5%, protein restricted).
- Research Organization:
- Univ. of Adelaide (Australia)
- OSTI ID:
- 6544754
- Journal Information:
- J. Pineal Res.; (United States), Vol. 5:5
- Country of Publication:
- United States
- Language:
- English
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MELATONIN
BIOLOGICAL EFFECTS
TRANQUILIZERS
RECEPTORS
BIOCHEMICAL REACTION KINETICS
BRAIN
CELL MEMBRANES
HYPOTHALAMUS
PROSTATE
RATS
TRACER TECHNIQUES
VISIBLE RADIATION
AMINES
ANIMALS
AROMATICS
AZAARENES
AZOLES
BODY
CELL CONSTITUENTS
CENTRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM AGENTS
DRUGS
ELECTROMAGNETIC RADIATION
GLANDS
HETEROCYCLIC COMPOUNDS
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ISOTOPE APPLICATIONS
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MALE GENITALS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
PSYCHOTROPIC DRUGS
PYRROLES
RADIATIONS
REACTION KINETICS
RODENTS
TRYPTAMINES
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550201* - Biochemistry- Tracer Techniques