Effects of Dopaminergic Blockade on the Sleep-Associated Changes of Luteinizing Hormone Pulsatility in Early Follicular Phase Women

Abstract

To investigate the dopaminergic role in the sleep-associated changes of luteinizing hormone (LH) pulsatile pattern, 11 normal cycling women were studied in the early follicular phase (EF, days 3 and 4) of their cycles before and after the administration of metoclopramide (MCP), a dopamine receptor antagonist. Twenty-four-hour infusions of either saline (NaCl 150 mmol/l–50 ml/h) or metoclopramide (MCP, 30 µg/kg/h) were conducted in a random sequence. Pulsatile LH activities were assessed in blood samples obtained at 15-min intervals for 48 h. Sleep was electrophysiologically confirmed by EEG during night hours (23.00–07.00 h). Significant sleep-associated decreases in LH pulse frequency (p < 0.05) and mean LH serum levels (p < 0.001) with a concurrent increase in LH pulse amplitude (p < 0.01) were observed during the saline control studies. MCP infusion failed to significantly modify the LH pulsatile activity during either the wake or sleep periods. In particular, it did not prevent the changes in LH pulsatility during sleep. This observation suggests that a dopaminergic mechanism does not critically contribute to the sleep-related changes in LH pulsatile activity in women during the early follicular phase.