Effects of MIF-I, sex, and weight on tonic immobility in lizards (Anolis carolinensis).
Three experiments were done with the lizard, Anolis carolinensis, as a follow-up on our previous work which showed that MIF-I reduced tonic immobility (TI) during the breeding season and that females had longer TI durations than males in the non-breeding season. In June, during the breeding season, 60 male and 60 female lizards were injected with 0.1 mg/kg of MIF-I or naloxone or the diluent vehicle and placed in small aquaria for ten minutes. TI was then induced in the small aquaria. Similar experiments were conducted in September and October (non-breeding season). There was a reduction in TI durations in MIF-I and naloxone-treated lizards of both sexes in June, but the differences between drug treatment groups and controls were not significant. In September and October, MIF-I treatment resulted in TI durations similar to controls but naloxone treatment resulted in slightly shorter durations. Increased TI duration in females as compared to males was seen during both seasons, but diminished during the breeding season. Weight was found to be a factor in male lizards, with males greater than or equal to 4.0 g showing significantly longer TI durations. The lack of a significant effect of MIF-I on TI durations during the breeding season is possibly due to changes in the experimental design from the earlier report.
D000818:Animals; D001835:Body Weight; D005260:Female; D008116:Lizards; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D012621:Seasons; D012737:Sex Factors
D009292:Narcotic Antagonists; D009270:Naloxone; D009075:MSH Release-Inhibiting Hormone