Brain serotonin 2A receptor binding: Relations to body mass index, tobacco and alcohol use

Manipulations of the serotonin levels in the brain can affect impulsive behavior and influence our reactivity to conditioned reinforcers. Eating, tobacco smoking, and alcohol consumption are reinforcers that are influenced by serotonergic neurotransmission; serotonergic hypofunction leads to increased food and alcohol intake, and conversely, stimulation of the serotonergic system induces weight reduction and decreased food/alcohol intake as well as tobacco smoking. To investigate whether body weight, alcohol intake and tobacco smoking were related to the regulation of the cerebral serotonin 2A receptor (5-HT2A) in humans, we tested in 136 healthy human subjects if body mass index (BMI), degree of alcohol consumption and tobacco smoking was associated to the cerebral in vivo 5-HT2A receptor binding as measured with 18F-altanserin PET. The subjects' BMI's ranged from 18.4 to 42.8 (25.2 ± 4.3) kg/m2. Cerebral cortex 5-HT2A binding was significantly positively correlated to BMI, whereas no association between cortical 5-HT2A receptor binding and alcohol or tobacco use was detected. We suggest that our observation is driven by a lower central 5-HT level in overweight people, leading both to increased food intake and to a compensatory upregulation of cerebral 5-HT2A receptor density.