Alcohol and alcoholism associated neurological disorders: Current updates in a global perspective and recent recommendations

Table 1 Major neurotransmitters involved in alcoholism

Name	Primary function	Location and distribution	Receptor	Disease-related	Comments	Ref.
Dopamine	Reward pathway; voluntary motions; motor circuit, cognitions	Hypothalamus, ventral tegmental area (mesolimbic area); most regions: Short medium and long axonal projections	D1, D2, D3, D4, D5	Parkinson’s disease, schizophrenia	Alcohol increases its use in nucleus accumbens, mediating its pleasurable impacts	Adermark et al[40]; Burns et al[41]
Serotonin (5-HT)	Mood regulation: Depression, aggression; intestinal movement control appetite; sleep; muscle control	Raphe nuclei in CNS; most regions: Project from pons and brainstem	5-HT1, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT4, 5-HT6, 5-HT7	Schizophrenia, depression, anxiety	Alcohol usage stimulation gives nausea, may also be linked to the pleasant effects of drinking	Bauer et al[44]
Gamma-Aminobutyric acid	Inhibits CNS	The limbic system, hippocampus, thalamus, basal ganglia; supraspinal interneuron	GABA A, GABA B	Anxiety disorder, seizures, epilepsy	Alcohol potentiates GABA activity, amnesia and sedation	Elholm et al[31]; Alasmari et al[45]
Glutamate	Long-term potentiation; learning; memory	CNS, peripheral nervous system; long neuron	NMDA, others	Seizures, schizophrenia	Alcohol blocks excitatory NMDA receptors, restricting it, causing amnesia, depressant impact	Marcinkiewcz[42]; Müller et al[43]

CNS: Central nervous system; GABA: Gamma-aminobutyric acid; NMDA: N-methyl-D-aspartate; 5-HT: 5-hydroxytryptamine.

Table 2 Summary of alcohol dehydrogenase and aldehyde dehydrogenase family gene

Enzyme	Gene name	Allelic variants	Amino acid differences between allele	Chromosomal location	Subunit components or protein name	Class
ADH	ADH1A			4q21-q23	α1α1	I
	ADH1B	ADH1B 1	Arg48, Arg370 (previously Arg47, Arg369)		β1β1	I
		ADH1B 2	His48, Arg370		β2β2
		ADH1B 3	Arg48, Cys370		β3β3
	ADH1C	ADH1C 1	Arg272, Ile350		γ1γ1	I
		ADH1C 2	Gln272, Val350		γ2γ2
	ADH4				π π	II
	ADH5				χ χ	III
	ADH6				μ μ	IV
	ADH7				σ σ	V
ALDH	ALDH1A1			9q21.13	Cytosolic aldehyde, dehydrogenase 1
	ALDH2	ALDH2 1		12q24.2	Mitochondrial aldehyde dehydrogenase

ADH: Alcohol dehydrogenase; ALDH: Aldehyde dehydrogenase.