Table 3.

Similarities and differences between pathological gambling (PG) and substance use disorders (SUDs) with regard to neurotransmitter system research findings (see text for details)

Neurotrans- mitter	PG results	SUD results: similarities/differences with PG
Dopamine	Limited impulsivity findings: In PD, agonist use associated with increased delay discounting in those with ICD.	Activity proposed to contribute to delay discounting in SUDs.
	Limited compulsivity findings: Equivocal results with agonists in animal models.	Activity proposed to contribute to compulsivity in SUDs.
	Elevated release during gambling task performance in some with PG (with and without PD), but also individual differences.	Substance use typically associated with release, but also individual differences.
	Equivocal findings with antagonist use	Also equivocal findings with antagonist use
Serotonin	Low levels of 5-HIAA in PG	Low levels of 5-HIAA in SUDs
	mCPP associated with subjective “high” in PG	mCPP associated with subjective “high” in SUDs
	Blunted growth hormone response to sumatriptan	Blunted growth hormone response to sumatriptan
	Evidence suggests role for 5HT1B receptor function	Evidence suggests role for 5HT1B receptor function
	Mixed results in efficacy of SSRIs for PG	Mixed results in efficacy of SSRIs for SUDs
Opioids	Evidence of involvement in gambling behavior and urges. Strong evidence for treatment efficacy of antagonists.	Evidence of involvement in substance use behavior and urges. Strong evidence for treatment efficacy of antagonists, particularly for alcohol and opioid dependence.
Glutamate	Preliminary evidence for efficacy of medications that alter transmission, with possible involvement in impulsive and compulsive behaviors.	Preliminary evidence for efficacy of medications that alter transmission, with possible involvement in impulsive and compulsive behaviors.
Norepineprine	Elevated activity in PG, particularly during gambling.	Elevated during use of some substances, particularly stimulants like cocaine.

5-HIAA: 5-hydroxyindoleacetic acid, PD: Parkinson’s Disease, ICD: impulse control disorder, mCPP: meta-chlorophenylpiperazine, SSRI: selective serotonin reuptake inhibitor