TABLE 2.

Studies investigating the effects of treatment with microbial cultures on neurotransmission and behavior.

Treatment	Species or strain	Behavioral outcomes	Molecular mechanisms	Reference
L. rhamnosus (109 cfu daily for 28 days)	Adult male BALB/c mice (10–11 weeks)	↓ anxiety and depressive-like behavior in OFT, SIH, EPM, fear conditioning (contextual and cued), and FST after L. rhamnosus chronic adnimistration; vagotomy prevented the anxiolytic and antidepressant effects of L. rhamnosus	Changes in expression of GABAAα2 and GABAB1b mRNA after L. rhamnosus chronic administration; vagotomy alone was sufficient to increase GABAAα2 mRNA in the hippocampus but prevented further changes induced by L. rhamnosus	[55]
B. infantis (daily for 14 days)	Sprague-Dawley rats	no effect on depressive-like behavior	↓ inflammatory markers (IFN-γ, TNF-α and IL-6 cytokines); ↑ plasma tryptophan and kynurenic acid; ↓concentrations of 5-HIAA (frontal cortex) and DOPAC (amygdaloid cortex)	[58]
L. rhamnosus (1 × 109 cfu daily for 4 weeks)	male BALB/c mice	↓ in anxiety and depression-related behaviors	↑ glutamate + glutamine and ↑ total N-acetyl aspartate + N-acetyl aspartyl glutamic acid at 2 weeks; ↑ GABA at 4 weeks	[50]
L. brevis FPA 3709 (48-h fermented black soybean milk at a dosage of 35 mg/kg b.w. including 2.5 mg GABA/kg b.w. for 28 days)	Male Sprague-Dawley rats	↓ in depressive behavior in FST comparable to the effect of fluoxetine	-	[51]

5-HIAA: 5-Hydroxyindoleacetic Acid; cfu: Colony-Forming Unit; DOPAC: 3,4-Dihydroxyphenylacetic Acid; FST: Forced Swim Test; EPM: Elevated Plus Maze; GABA: Gamma-Aminobutyric Acid; IFN-γ: Interferon Gamma; IL-6: Interleukin-6; OFT; Open Field Test; SIH: Stress-Induced Hyperthermia; TNF-α: Tumor Necrosis Factor Alpha.