Morphofunctional Evidence for the Involvement of Hypothalamic Dopaminergic and GABAergic Neurons in the Mechanisms of Photoperiod-Dependent Prolactin Release in the Mink
| Autor: | Claude Gril, Jean Boissin, Line Boissin-Agasse, Gisèle Roch, Marcel Tappaz |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Male
Periodicity endocrine system medicine.medical_specialty Light Tyrosine 3-Monooxygenase Dopamine Endocrinology Diabetes and Metabolism Glutamate decarboxylase Hypothalamus Fluorescent Antibody Technique Biology Cellular and Molecular Neuroscience Endocrinology Internal medicine medicine Animals gamma-Aminobutyric Acid Neurons Tyrosine hydroxylase Glutamate Decarboxylase Endocrine and Autonomic Systems Dopaminergic Immunohistochemistry Prolactin Mink Median eminence GABAergic hormones hormone substitutes and hormone antagonists medicine.drug |
| Zdroj: | Neuroendocrinology. 53:537-542 |
| ISSN: | 1423-0194 0028-3835 |
| Popis: | This study was designed to examine possible relationships between the photoperiodic regulation of prolactin secretion and the activity of dopaminergic and GABAergic neurons projecting to the external layer of the median eminence. The study was carried out on the mink whose remarkable photosensitivity has been clearly demonstrated. The animals were reared in short (4L:20D) or long (20L:4D) photoperiods. The experiment began in November when day length is short (9.5 h). Dopaminergic and GABAergic neurons were studied using immunocytochemical methods allowing evaluation of the immunoreactivities of tyrosine hydroxylase (TH) and glutamate decarboxylase (GAD), which are respective markers of these neurons. The results were quantified by image analysis. The plasma prolactin level of animals maintained in 4L:20D decreased after 60 days and TH and GAD immunoreactivity were strongly stimulated. After 110 days, the prolactin concentration and TH and GAD immunoreactivity recovered their starting levels. In animals maintained in 20L:4D, the prolactin level was 3 times higher than at the beginning of the photoperiodic treatment but only dopaminergic neurons showed a change, i.e. a decrease in immunoreactivity. At the end of the experiment, prolactin secretion was no longer affected by the stimulatory effect of long-day treatment, and TH immunoreactivity remained low. These results confirm the generally accepted concept that dopaminergic neurons are potent PIF-producing components. GABAergic hypothalamic system appears to be implicated in photoperiodic PRL regulation, but this remains to be clearly demonstrated. |
| Databáze: | OpenAIRE |
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