Table 2.
Changes in neuroendocrine system of germ-free (GF) mice
| Mouse strain | HPA axis (GF vs colonized) | Related systems | Reference |
|---|---|---|---|
| GF BALB/c mice ♂ | ↑ CORT (after restraint stress) ↑ CRF mRNA + protein (hypothalamus) ↓ GR mRNA (cortex) |
↓ NR-1 mRNA (cortex) ↓ NR-2 mRNA (cortex + hippocampus) ↓ BDNF protein (cortex + hippocampus) |
[93] |
| GF BALB/c mice | ↓ NE and DA turnover (hippocampus, striatum, brainstem) ↓↑ 5-HT turnover (striatum, brainstem) |
[101] | |
| GF Swiss Webster mice ♀ | ↑ CORT (48 h after arrival) | ↓ NR2b mRNA (amygdala) ↑ BDNF mRNA (hippocampus) ↓ 5HT1A mRNA (hippocampus) |
[98] |
| GF NMRI mice ♂ | ↑ NE, DA, and 5-HT turnover (striatum) ↓ NGFI-A mRNA (PFC) ↓ BDNF mRNA (hippocampus + amygdala) ↑ DAD1 receptor mRNA (hippocampus) ↑ synaptophysin + PSD-95 (striatum) |
[97] | |
| GF Swiss Webster mice ♀+♂ | ↑ CORT (after novel environment stress) | ↓ BDNF mRNA (hippocampus, male) ↑ 5-HT (hippocampus, male) ↑ 5-HIAA (hippocampus, male) ↓ TNF-α (splenocytes + LPS) ↓ kynurenine/tryptophan (plasma) |
[99] |
| GF stress-sensitive F344 rats ♂ | ↑ CORT after OFT ↑ CRF mRNA (PVN) ↓ GR mRNA (hippocampus) |
↓ DA turnover (frontal cortex, hippocampus, striatum) | [102] |
| GF C57BL/6N mice ♀+♂ | ↔ CORT after MS | ↑ BDNF protein after MS (hippocampus) ↑ 5-HT (hippocampus) ↓ NE (hippocampus) |
[100] |
HPA = hypothalamic–pituitary–adrenal; CORT = corticosterone; CRF = corticotropin-releasing factor; GR = glucocorticoid receptor; NR = N-methyl D-aspartate receptor; BDNF = brain-derived neurotrophic factor; NE = norepinephrine; DA = dopamine; 5-HT = 5-hydroxytryptamine; NR2b = 2b subunit of the N-methyl-D-aspartate receptor; NGFI-A, nerve growth factor-inducible clone A; PFC = prefrontal cortex; PSD-95 = postsynaptic density protein 95; 5-HIAA = 5-hydroxyindole acetic acid; TNF = tumor necrosis factor; LPS = lipopolysaccharide; OFT = open-field test; PVN = paraventricular nucleus of the hypothalamus; MS = maternal separation