Objective: 

Brain–derived neurotrophic factor (BDNF) is accepted to play a critical role in the maintenance of nicotine (NIC) addiction. Our aim was to study possible changes in brain BDNF mRNA levels following chronic NIC intake in rats, preselected according to NIC preference.

Methods: 

Adult Sprague Dawley rats were exposed to a 2-bottle, free choice oral NIC self administration from adolescence to adulthood (23 weeks) and NIC intake was used to determine preference as adults. Control (CONT) rats received water from both bottles. There were 6 groups (n=7–10/group): Female or male MAX or MIN and CONT. Total RNA was extracted from the frontalcortex, striatum and hippocampus; semi-quantitative RT-PCR was performed for BDNF mRNA expression.

Results: 

ANOVAs showed main effects of regions (p<0.001), sex (p<0.005), NIC preference (p<0.05) and a sex x regions interaction (p<0.001). In the frontal cortex, the MAX male rats was lower than MAX females (p<0.05). Similarly, in the hippocampus, MAX males had the lowest levels of all. Hippocampal BDNF mRNA expression in the MAX male group was significantly lower than females with the same preference (p<0.05) or CONT male rats (0.01). These results suggest sex and region specific regulation of BDNF mRNA expression by NIC in rats; in the frontal cortex and hippocampus, BDNF mRNA levels are lower in MAX male rats than MAX females and CONTs.

Conclusions: 

NIC preference and intake did not have an effect on regulating BDNF mRNA levels in the female rats. If similar regulatory mechanisms occur in humans, heavy smoker men may be facing the negative consequences of reduced BDNF levels in brain regions related to cognition and affect.