Table 2. Involvement of 5-HT₄ receptor on the 5-HT induced IVF success.

	No. of eggs	No. of two-cell embryos	Two-cell embryos (%)
Vehicle	208	92	43.39 ± 3.42 *
100 nM 5-HT	110	71	64.15 ± 5.02
GR	125	49	38.27 ± 7.38
100 nM 5-HT + GR	96	40	43.16 ± 8.76

Each value indicated successful IVF in the presence of 5-HT and GR. Sperm and COCs were co-incubated for 2 h, and the data represent the mean ± standard deviation. (Vehicle) the medium with 0.1% (v/v) pure water and 0.1% (v/v) dimethyl sulfoxide as the vehicle; (100 nM5-HT) the medium with 100 nM 5-HT and the vehicle; (GR) the medium with 1

μM GR and the vehicle; (100 nM 5-HT + GR) the medium with 100 nM 5-HT and 1 μM GR and the vehicle. * Significant differences compared with “Vehicle” (P < 0.05). COC, cumulus-oocyte complex; GR, 5-HT₄ receptor antagonist (GR113808); IVF, in vitro fertilization.