In Addiction Biology Peter Karel and Judith Homberg showed that rats lacking the serotonin transporter show increased cocaine, but unaltered sucrose, self-administration.To examine the potential neural mechanisms underlying the vulnerability to cocaine addiction in serotonin transporter knockout rats, the rats were subjected to ex-vivo ultra-high resolution MRI. The serotonin transporter knockout rats were found to have a smaller amygdala, independent of sucrose or cocaine self-administration. In addition, serotonin transporter genotype and reward type were found to interact for the volume of the dorsal raphe, the brainstem nucleus were serotonergic neurons are located. These data show that the amygdala and dorsal raphe play an important role in vulnerability to cocaine addiction.
Ultrahigh-resolution MRI reveals structural brain differences in serotonin transporter knockout rats after sucrose and cocaine self-administration.