Abstract
The effects of steroid sex hormones on low (0.08 mg/kg sc)-apomorphine-induced yawning in rats (Wistar, Cpb:WU) were studied. Yawning was less in female than in male rats. Castration of male, but not of female rats reduced yawning considerably. Three days treatment with testosterone propionate (50 or 100 μg/rat daily) or dihydrotestosterone (same doses) increased yawning, both in castrated male and in intact and ovariectomized female rats. Androgenic effects of testosterone propionate were larger than those of dihydrotestosterone, whereas effects on yawning were similar. It is suggested that apomorphine-induced yawning is under androgenic influence and that estrogens play no or a minor role.
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