The maturational onset of the 5-HT mediated head twitch in mice

Abstract The effect of elevated brain serotonin (5-hydroxytryptamine, 5-HT) on the head twitch was examined to determine an age of onset in mice for this 5-HT mediated motor activity. Two different treatments were used to elevate 5-HT: 100 mg/kg L-tryptophan with 100 mg/kg pargyline; and 100 mg/kg 5-HTP with 25 mg/kg carbidopa. Mice from ages 14 to 42 days postpartum were examined. Both treatments showed an onset of the head twitch at 15 days. Juvenile mice of 15–18 days appeared to differ in their response to the two treatments. Although 5-HTP and carbidopa stimulated head twitches, 5-HTP alone had a greater stimulatory effect at these ages, while in the other experiment only those animals receiving the combined tryptophan and pargyline treatment showed significant responses.