Table 1.

Common species of gut microbiota and effects of their metabolites on the central nervous system

Gut microbiota	Metabolites	Effects on the central nervous system function	References
Lactobacillus, Bifidobacterium	Gamma-aminobutyric acid (GABA)	The predominant inhibitory neurotransmitter, regulates mood, behavioral and cognitive functions	[37]
Bifidobacterium infantis, Streptococcus, Escherichia, Enterococcus, Lactococcus, Lactobacillus, Candida	Serotonin (5-HT)	Neurotransmitters, regulate emotions	[38]
Escherichia, Bacillus, Lactococcus, Lactobacillus, Streptococcus	Dopamine	Regulate mental activities and motor functions, cognitive functions such as learning and memory	[38]
Lactobacillus, Bacillus	Acetylcholine	Cognitive, memory, social life ability, self-care ability, and emotional personality	[39]
Bacteroides, Bifidobacterium, Propionibacterium, Eubacterium, Lactobacillus, Clostridium, Roseburia, Prevotella	Short-chain fatty acids (SCFA)	Decrease permeability of the blood-brain barrier (BBB), promote the synthesis and secretion of neurotransmitters and hormones, reduce inflammation	[40]
Lactococcus, Lactobacillus, Streptococcus, Enterococcus	Histamine	Regulate sleep and cognition	[41, 42]