Photoperiodic Modification of Opiate but not β-Adrenergic or Benzodiazepine Binding Sites in Hamster Brain

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Abstract
Exposure to short photoperiods induces gonadal regression in the golden hamster. This is accompanied by a fall in serum gonadotropins and changes in hypothalamic neurotransmitter turnover. We have attempted to correlate these changes with alterations in neurotransmitter receptor binding parameters. Compared to hamsters held in long photoperiods, opiate ([3H] naloxone) binding in hamsters exposed to short photoperiods is elevated in whole brain and in cerebral cortex but not in hypothalamus. However, β-adrenergic ([3H] dihydroalprenolol) and benzodiazepine ([3H] flunitrazepam) binding are unaffected in whole brain, cerebral cortex or hypothalamus. Thus, changes in hypothalamic noradrenaline turnover rate previously reported may not be correlated with changes in β-adrenergic binding.