In Vivo Correlates of Central Serotonin Function after High-Dose Fenfluramine Administration

Area of Science:

• Neuroendocrinology
• Neuropharmacology
• Serotonin Systems

Background:

• High-dose fenfluramine (FEN) is known to deplete central serotonin (5-HT) in animals.
• Functional impairments from FEN-induced 5-HT depletion are challenging to identify.
• Neuroendocrine function is sensitive to central 5-HT levels.

Purpose of the Study:

• To investigate neuroendocrine responsiveness in rats following repeated high-dose FEN administration.
• To determine if FEN treatment alters pituitary hormone secretion.
• To assess the utility of neuroendocrine challenge tests for detecting FEN-induced neurotoxicity.

Main Methods:

• Male rats received repeated high-dose FEN (20 mg/kg twice daily for 4 days) or saline.
• Rats were challenged with intravenous FEN (1.5 & 3 mg/kg) or saline at 1 and 2 weeks post-treatment.
• Plasma prolactin and corticosterone levels were measured via radioimmunoassay.

Main Results:

• Acute FEN challenge elevated prolactin and corticosterone in all rats.
• FEN-induced hormone responses were significantly blunted in rats previously treated with FEN (p <0.01).
• Repeated FEN dosing reduced 5-HT levels by >50% in the hypothalamus, amygdala, and hippocampus.

Conclusions:

• High-dose FEN alters central 5-HT systems involved in pituitary hormone secretion.
• Neuroendocrine challenge paradigms can identify functional 5-HT deficits induced by FEN.
• Neuroendocrine challenge tests may reliably detect FEN-induced neurotoxicity in humans.