CHRONIC NICOTINE REVERSES AGE-ASSOCIATED INCREASES IN TAIL-FLICK LATENCY AND ANXIETY IN RATS

The chronic consumption of low doses of nicotine in drinking water for two years consistently increased the sensitivity of rats to a nocicep tive thermal stimulus (tail-flick test), but reduced aversiveness in t he elevated plus-maze test, relative to the responses of age-matched c ontrols in these tests. The responses of aged nicotine-consuming rats were indistinguishable from those of young adult rats that did not rec eive nicotine. To determine whether these effects were due to a nicoti ne-induced retardation of age-related changes, young adult rats were s imilarly treated with nicotine for three months and similar changes in the tail-flick latency and performance in the plus-maze test were obs erved during nicotine consumption. These changes were reversed followi ng withdrawal from nicotine. It is concluded that the maintenance of c irculating low levels of nicotine (and/or its metabolites) increased t he nociceptive sensitivity of the rats and reduced their aversions in the plus-maze test regardless of their age.