The Dopaminergic Reward System and Leisure Time Exercise Behavior: A Candidate Allele Study

Table 1

Allele-specific hypotheses.

Gene	Variant	Allele	Expected effect	Reference number	Effect on dopamine level*	Effect on exercise behavior*
DRD1	rs265981	A	Decreased DRD1 expression levels	[24]	↓	↓
DRD2	rs6275	G	Increased DRD2 expression levels	[25]	↓	↓
	rs1800497	A	Reduced number of (inhibitory) D2 receptors	[28, 29]	↑	↑
DRD3	rs6280	C	Higher affinity for dopamine → decreased transmission	[31]	↓	↓
DRD4	rs1800955	C	Increased DRD4 expression levels	[32, 33]	↓	↓
	VNTR: 7 allele		Lower affinity for dopamine → increased transmission	[34, 35]	↑	↑
DRD5	VNTR: 148 allele		Decreased DRD5 expression levels	[36]	↓	↓
DBH	rs1611115	C	Higher DBH activity	[37, 38]	↓	↓
	rs2519152	T	Lower DBH activity	[39]	↑	↑
DAT1	VNTR: 480 allele		Higher DAT activity → higher reuptake	[40, 41]	↓	↓
COMT	rs4680	G	Methionine → slower degradation of dopamine	[42]	↑	↑

^∗↑: increase; ↓: decrease.