Regulation of novelty seeking by midbrain dopamine D2/D3 signaling and ghrelin is altered in obesity

OBJECTIVE: To investigate the relationship of novelty seeking traits (NS) with midbrain dopamine (DA) receptors and acyl ghrelin levels (AG) in normal weight (NW) and obese females. NS predict addictive behaviors and are hypothesized to contribute to eating behaviors. In healthy, NS are negatively associated with DA receptors in the substantia nigra (SN). We hypothesized that obesity would influence the regulation of NS by DA signaling and AG. DESIGN AND METHODS: We used PET scanning to measure DA type 2/type 3 receptor (D2/D3R) binding potential (BP(ND)) in the SN. Participants completed Tridimensional Personality Questionnaire-Novelty-Seeking Scale (TPQ-NS) and AG were measured. RESULTS: In 8 NW and 19 obese (BMI 22 vs 38 kg/m(2)), TPQ-NS (16 vs15) and SN D2/D3R BP(ND) (2.48vs2.66) were similar, while AG higher (256vs60, p<0.01), respectively. D2/D3R BP(ND) and TPQ-NS had a negative relationship in NW (r=−0.7) but not in obese (p>0.10). AG and TPQ-NS were positively correlated in NW (r=0.9) but not in obese (p>0.10). D2R BP(ND) and AG were negatively correlated in NW (r=−0.8) but positively in obese (r=0.6). CONCLUSION: Obese do not maintain posited regulatory relationships for NS to either midbrain D2/D3R availability or AG present in NW. Also opposite relationships exist for NW and obese between SN D2/D3R availability and AG. The altered regulation of NS in obesity needs to be further explored.