Sex and day-night differences in opiate-induced responses of insular wild deer mice, Peromyscus maniculatus triangularis

Sex and rat strain determine sensitivity to κ opioid-induced antinociception

“…In particular, spiradoline was on average 2.5-fold more potent in male than female SD rats at each of the water temperatures tested, and U50,488 was 3.0-fold more potent in female than male Lewis rats at the 50°C water temperature. These findings corroborate previous investigations showing either no sex differences or small sex differences in the antinociceptive effects of higher efficacy κ opioids (Kavaliers and Innes 1987;Bartok and Craft 1997;Craft et al 1998;Negus and Mello 1999;Patrick et al 1999;van Haaren et al 2000).…”

“…For example, in SD rats U69,593 and bremazocine have been shown to be more effective in males than females, equally effective in males and females, and more effective in females than males (Bartok and Craft 1997;Craft et al 1998;Tershner et al 2000;van Haaren et al 2000;Craft and Bernal 2001). Similarly, U50,488 produces greater antinociception in male than female deer mice (Kavaliers and Innes 1987), is more potent in male than ovariectomized female rhesus monkeys (Negus and Mello 1999), and is equally potent in male and female Swiss Webster mice (Patrick et al 1999). The specific parameters of the task, drug dose, nociceptive assay, and drug pretreatment interval may contribute to these discrepant findings.…”

Persistent pain model reveals sex difference in morphine potency

“…The results of the present study demonstrating a significant sex difference in morphine potency are consistent with previous studies using acute pain models in which morphine was injected either systemically (1,11,31,32,36,48), or directly into the RVM (6) or PAG (39,40). The results of animal studies parallel recent findings in humans, indicating that females require 30% more morphine than males to achieve a comparable level of analgesia for relief of postsurgical pain (9).…”

Gonadal steroid hormone modulation of nociception, morphine antinociception and reproductive indices in male and female rats

“…Sex differences in opioid antinociception also are widely reported in rodents, although they tend to be in the opposite direction to those observed in humans. For example, morphine was significantly more potent or produced a greater effect in male than in female mice (Kavaliers and Innes, 1987;Lipa and Kavaliers, 1990;Candido et al, 1992) and rats (Baamonde et al, 1989;Cicero et al, 1996;Craft et al, 1999;Cook et al, 2000). Variables that may influence the magnitude of sex differences in opioid antinociception in rodents include opioid efficacy/selectivity, intensity of the noxious stimulus used in the pain test, and subject genotype (i.e.…”