The amygdala, especially its central nucleus (CeA), is one of the key brain structures regulating fear, anxiety and stress responses and is also involved in gut microbiota signal processing. Amygdala hyperactivity, as well as microbiota alterations, plays an important role in the pathophysiology of anxiety disorders, depression or post-traumatic stress disorder (PTSD). The present study determines whether 3 weeks of galactooligosaccharide (GOS) supplementation alleviates behavioural, haematological, immunological and gut microbiota disturbances induced by long-term electrical stimulation of the CeA in rats (Stim). The unsupplemented Stim group showed locomotor hyperactivity and higher anxiety (measured with an actometer and the elevated plus maze, respectively), as well as a decrease in white blood cells (WBCs), lymphocytes (LYMs), red blood cells (RBCs) and platelets (PLTs); an elevation of TNFα; a reduction in IL-10 concentration in plasma; and microbiota alterations as compared to the control (Sham) group. GOS supplementation alleviated all these Stim-induced adverse effects or even normalised them to the sham group level. The effect of GOS was comparable to citalopram and even more effective in WBC and PLT normalisation and IL-10 induction. The obtained results indicate the high therapeutic potential of GOS in anxiety and stress-related disorders. GOS supplementation may support conventional therapy or the prevention of PTSD, depression and anxiety disorders.

Alzheimer’s disease (AD) is characterized by impaired neurotrophic support, oxidative stress, and metabolic dysfunction. Using the intracerebroventricular streptozotocin (ICV-STZ) rat model of sporadic AD, we investigated whether vitamin D₃ (VitD₃) and dimethyl fumarate (DMF), administered alone or in combination, modulate hippocampal neurotrophin-related signaling and redox balance. Animals were assigned to SHAM, STZ, VITD, DMF, and COMBO groups, representing control, ICV-STZ, VitD₃-treated ICV-STZ, DMF-treated ICV-STZ, and combined VitD₃ + DMF-treated ICV-STZ animals, respectively. Hippocampal neurotrophin processing (proBDNF and mature BDNF), downstream signaling (Akt and pAkt), IGF-1 content, mitochondrial oxoglutarate dehydrogenase (OGDH) content, citrate synthase (CS) activity, and glutathione peroxidase (GPx) activity were assessed. STZ administration showed a trend toward reduced mature BDNF content compared with the SHAM group (p = 0.07), whereas combined VitD₃ and DMF treatment significantly increased mature BDNF content compared with the STZ group. The mature BDNF/proBDNF ratio was reduced in the STZ group compared with the SHAM group and tended to be higher in the COMBO group compared with the STZ group (p = 0.09). proBDNF content remained unchanged. IGF-1, pTrkB, total Akt, and pAkt content did not differ significantly between groups. The pAkt/Akt ratio showed a trend toward reduction in the STZ group compared with SHAM group (p = 0.09). GPx activity increased in the STZ group, while CS activity and OGDH content were not significantly altered. These findings indicate that STZ-induced neurodegeneration is characterized by redox-associated uncoupling of neurotrophic signaling rather than mitochondrial disruption. Combined VitD₃ and DMF treatment partially modulated neurotrophic signaling, supporting a limited but measurable neuroprotective effect.