An overview of developments in research on recovery from brain injury

Testing the combined effects of probiotics and prebiotics against neurotoxic effects of propionic acid orally administered to rat pups

The present study investigated the combined effects of mixed probiotic and bee pollen on brain intoxication induced by propionic acid (PPA) in rat pups. Thirty western albino rats were divided into five groups, six animals each: (1) Control group receiving phosphate-buffered saline; (2) Probiotic and bee pollen-treated group being administered at the same dose with 200 mg/kg body weight; (c) PPA-treated group receiving a neurotoxic dose 250 mg/kg body weight of PPA for 3 days; (d) Therapeutic group being administered the neurotoxic dose of PPA followed by probiotic and bee pollen treatment 200 mg/kg body weight; (e) Protective group receiving probiotic and bee pollen mixture treatment followed by neurotoxic dose of PPA. Selected biochemical parameters linked to oxidative stress, energy metabolism, and neurotransmission were investigated in brain homogenates from all the five groups. PPA treatment showed an increase in oxidative stress markers like lipid peroxidation coupled with a significant decrease in glutathione level. Impaired energy metabolism was ascertained via the alteration of creatine kinase (CK) and lactate dehydrogenase (LDH) activities. Dramatic increase of Na+ and K+ concentrations together with a decrease of GABA and IL-6 and an elevation of glutamate levels in PPA-treated rat's pups confirmed the neurotoxicity effect of PPA. Interestingly, the mixed probiotic and bee pollen treatment were effective in restoring the levels of glutamate, GABA, and IL-6 in addition to normalizing the levels of lipid peroxidation and glutathione and the activities of CK and LDH. The present study indicates that mixed probiotic and bee pollen treatment can improve poor detoxification, oxidative stress, and neuroinflammation as mechanisms implicated in the etiology of autism.

Probiotic treatment reduces the autistic-like excitation/inhibition imbalance in juvenile hamsters induced by orally administered propionic acid and clindamycin

Increasing evidence suggests that the gut microbiota plays a key role in the central nervous system (CNS), and alterations of the gut microbiota composition due to environmental factors can contribute to neurodevelopmental disorders. Animal modeling may help to identify drugs that can normalize the altered gut microbiota and thereby ameliorate abnormal brain signaling pathways. The purpose of the present study was to investigate the therapeutic potency of probiotics such as Bifidobacteria and Lactobacilli on glutamate excitotoxicity as a neurotoxic effect induced by clindamycin and propionic acid (PPA) in juvenile hamsters. Fifty young golden Syrian hamsters weighing between 60 and 70 g were enrolled in the study. The hamsters were randomly divided into five groups, each with ten hamsters. The hamsters in the control group only received phosphate-buffered saline orally. The PPA-treated group received a neurotoxic dose of 250 mg PPA/kg body weight (BW)/day for three days. The clindamycin-treated group received 30 mg clindamycin/kg BW as a single orogastric dose on the day the experiment started. The two therapeutic groups received the same doses of PPA and clindamycin followed by 0.2 g probiotic/kg BW for three weeks. Biochemical parameters related to glutamate excitotoxicity were investigated in brain homogenates from each group of hamsters. Additionally, the development of pathogenic bacteria was monitored in stool samples from all groups. The microbiology results of the present study revealed descriptive changes in the fecal microbiota and the appearance of Clostridium species in the hamsters treated with clindamycin and PPA. Additionally, the effectiveness of the probiotic in the restoration of the normal gut microbiota was demonstrated. Moreover, clindamycin and PPA were found to induce a significant depletion of Mg²⁺ and γ-aminobutyric acid (GABA) and a remarkable increase in the Na⁺/Mg²⁺ and glutamate/GABA ratios but non-significant changes in the absolute levels of K⁺, Na⁺ and glutamate. The bacteria overgrowth induced by PPA and clindamycin in the present study effectively showed signs of neuronal toxicity. The study indicates that probiotics can be used safely to ameliorate glutamate excitotoxicity mostly through increasing depleted GABA and Mg²⁺ and decreasing the excitatory neurotransmitter, glutamate.

Studies on the influence of enriched-environment housing combined with systemic administration of an alpha2-adrenergic antagonist on spatial learning and hyperactivity after global ischemia in rats

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether an enriched housing environment and/or systemic administration of the alpha2-adrenergic receptor antagonist atipamezole facilitate the rate of spatial learning after global ischemia in rats.

METHODS

Carotid arteries were closed for 20 minutes after permanent cauterization of vertebral arteries on the previous day. Enriched-environment housing and drug/saline treatment were begun 3 days after ischemia. For rehabilitation, housing in an enriched environment was combined with exploration in a labyrinth. Behavioral tests (the open-arena test and water-maze learning set task) were performed after 1-week periods of drug/saline treatment three times. In addition, the open-arena test was performed to evaluate the baseline level of animals 2 days after the induction of ischemia and at the end of the experiment, when the water-maze task was assessed in another room.

RESULTS

Rats housed in an enriched environment after ischemia showed better acquisition of the water-maze learning set task after 1 week of housing. The influence of atipamezole treatment on this parameter did not reach statistical significance. In the open-arena test, ischemic animals were slightly hyperactive; however, this symptom was eliminated by housing in an enriched environment.

CONCLUSIONS

The present data suggest that housing in an enriched environment facilitates the rate of spatial learning in rats with global ischemia. Rehabilitation also alleviated the hyperactivity observed in ischemic animals.

Functional recovery after brain infarction: plasticity and neural transplantation

In the past, little attention has been given to the role of brain plasticity for the long term functional outcome in experimental stroke although there is substantial evidence for plasticity in other experimental models of neurological disorders. Under clinical conditions, functional improvement occurs in most stroke survivors during the initial months after the ischemic incidence. Recent PET studies in stroke patients, investigated two months or later after stroke, indicate a considerable potential for functional plasticity in the adult human cerebral cortex. Research aimed at the identification of the mechanisms underlying functional recovery should be given high priority, particularly with regard to environmental factors and pharmacological interventions. Pilot experiments of environmental enrichment significantly improved the functional outcome of laboratory animals after brain infarction. Fetal neocortical tissue grafted into the infarcted area in adult rats received afferent fibres from the intact brain and responded to contralateral sensory stimulation with increased metabolic activity, indicating functional integration between neocortical grafts and host afferent systems. However, reciprocal connections from the graft to the host tissue were rare, and it remains to be shown whether grafting will be able to restore the complex cortical organization of the infarcted tissue.