Abstract
Spontaneous intracerebral hemorrhage (sICH) is the deadliest stroke subtype. There is strong evidence that tobacco use / smoking increases the risk of sICH, and some epidemiological studies have observed sex differences in sICH outcomes. However, systematic controlled studies on the effect of tobacco / smoking on post-sICH outcomes in both sexes are lacking. Therefore, we determined the effect of nicotine exposure on outcomes following collagenase-induced sICH both sexes. Young animals of both sexes were randomly divided into nicotine (4.5 mg / kg / day b.w.) and vehicle (saline) treatment groups (using osmotic pumps for two to three weeks). sICH in females was induced during the diestrous stage of estrous cycle. sICH was induced by collagenase injection into the right striatum and ~24 hours later, neurological scores were evaluated, rats were euthanized, and brains were sectioned to measure hematoma volume. Hematoma volumes for male rats was 42% higher (p<0.01) in the nicotine-treated group (139 ± 9 mm 3 , n=10) versus vehicle-treated group (98 ± 9 mm 3 , n=10). Hematoma volumes for female rats was 48% higher (p<0.01) in the nicotine-treated group (134 ± 11 mm 3 , n=10) versus vehicle-treated group (90 ± 7 mm 3 , n=10). Hematoma volumes for the vehicle and nicotine-treated male groups were not different from their respective female groups. The neurological score for the nicotine-treated male group (9.3 ± 0.6) was significantly higher (p<0.05) when compared to vehicle group (7.4 ± 0.6). The neurological score for the nicotine-treated female group (10.7 ± 0.2) was significantly higher (p<0.001) than the vehicle group (7.7 ± 0.7). The neurological score for the vehicle-treated male group was not different from its respective female group. However, the neurological score for the nicotine-treated male group was significantly lower than the female group. Our results show that chronic nicotine exposure increases hematoma volume post-sICH in animals of both sexes. Future studies into the mechanism of nicotine-induced increase in hematoma growth following sICH are required. Support: James and Esther King Biomedical Research Grant 9JK08
