The serotonin (5-HT) _1A/1B agonist RU 24969 robustly increases the locomotor activity of adult male rats and mice; however, studies using selective antagonists alternately report that 5-HT_1A, 5-HT_1B, or both receptor types mediate RU 24969's locomotor activating effects. The purpose of the present study was to extend these past findings by administering a selective 5-HT₁ agonist and/or antagonists to male and female preweanling rats. This age group was tested because younger rats often exhibit psychopharmacological responses that are quantitatively or qualitatively different from adult rats. In a series of experiments, male and female preweanling rats were pretreated with vehicle, the 5-HT_1A antagonist WAY 100635 (0.5, 1, 5, or 10 mg/kg), or the 5-HT_1B antagonists NAS-181 (5 or 10 mg/kg) or SB 216641 (5 or 10 mg/kg) 30 min before assessment of locomotor activity. Rats were injected with saline or RU 24969 immediately prior to testing. Results showed that RU 24969 (0.625, 1.25, 2.5, or 5 mg/kg) significantly increased the locomotor activity of both male and female preweanling rats (no sex differences were apparent). Antagonism of either the 5-HT_1A or the 5-HT_1B receptor was sufficient to significantly reduce the locomotor activity of RU 24969-treated preweanling rats. Unexpectedly, NAS-181 did not act as a silent receptor antagonist, as both doses of NAS-181 significantly increased the locomotor activity of saline-treated preweanling rats. In sum, the present results show that both the 5-HT_1A and 5-HT_1B receptor systems mediate locomotion during the late preweanling period, and this mediation does not vary according to sex.

血清素（5-HT）_{1A / 1B}激动剂RU 24969可以显着提高成年雄性大鼠和小鼠的运动能力；但是，使用选择性拮抗剂的研究交替报告了5-HT _1A，5-HT _1B或这两种受体类型均介导RU 24969的自发激活作用。本研究的目的是通过对雄性和雌性断奶前大鼠施用选择性5-HT ₁激动剂和/或拮抗剂来扩展这些过去的发现。对这个年龄组进行了测试，因为年幼的老鼠通常表现出与成年老鼠在数量或质量上有所不同的心理药理反应。在一系列实验中，雄性和雌性断奶前大鼠用媒介物5-HT _1A预处理评估前30分钟，拮抗剂WAY 100635（0.5、1、5或10 mg / kg）或5-HT _1B拮抗剂NAS-181（5或10 mg / kg）或SB 216641（5或10 mg / kg）运动活动。在测试前立即给大鼠注射生理盐水或RU 24969。结果显示，RU 24969（0.625、1.25、2.5或5 mg / kg）显着增加了雄性和雌性断奶前大鼠的运动能力（没有明显的性别差异）。5-HT _1A或5-HT _1B的拮抗作用该受体足以显着降低RU 24969处理的断奶前大鼠的运动能力。出乎意料的是，NAS-181并未充当沉默受体拮抗剂，因为两种剂量的NAS-181均显着提高了盐水治疗的断奶前大鼠的运动能力。总而言之，目前的结果表明5-HT _1A和5-HT _1B受体系统均在断奶前后期介导运动，并且这种介导不会随性别而变化。