Serotonin-enhanced hyperactivation of hamster sperm.

The effects of serotonin on reproductive function were examined using hamster spermatozoa. When serotonin at concentrations from 1 fmol/l to 1 μmol/l was added to modified Tyrode's albumin lactate pyruvate (mTALP) medium, hyperactivation was significantly enhanced. Agonists and antagonists of 5-hydroxytryptamine hydrochloride (5-HT) receptors (5-HT(2) and 5-HT(4) receptors) were added to the medium. Both 5-HT(2) and 5-HT(4) receptor agonists significantly enhanced hyperactivation, although the effect was greater than the former. However, both 5-HT(2) and 5-HT(4) receptor antagonists significantly suppressed serotonin-enhanced hyperactivation, with the former suppressing stimulation by a lower concentration of serotonin than the latter. These results indicate that serotonin enhances hyperactivation via 5-HT(2) and/or 5-HT(4) receptors in a dose-dependent manner.