Sex differences in cocaine- and nicotine-induced antinociception in the rat

Several recent reports describe sex differences in opioid antinociception. The present study examined sex differences in stimulant-induced antinociception. On the 50 degreesC hotplate test, cocaine (0.1-1.0 microgram i.c.v.) produced dose- and time-dependent increases in response latency in male but not female Sprague-Dawley rats. In contrast, nicotine (3-30 microgram i.c.v.) produced increases in hotplate latency in both sexes, but produced greater effects in females; nicotine also decreased spontaneous locomotor activity significantly more in females than in males. These sex differences probably are not due to differential pharmacokinetics, and underscore the importance of including female subjects in experimental drug research.