Whole-brain monosynaptic outputs and presynaptic inputs of GABAergic neurons in the vestibular nuclei complex of mice.

GABAergic neurons in the vestibular nuclei (VN) participate in multiple vital vestibular sensory processing allowing for the maintenance and rehabilitation of vestibular functions. However, although the important role of GABA in the central vestibular system has been widely reported, the underlying neural circuits between VN GABAergic neurons and other brain functional regions remain elusive, which limits the further study of the underlying mechanism. Hence, it is necessary to elucidate neural connectivity based on outputs and inputs of GABAergic neurons in the VN. This study employed a modified rabies virus retrograde tracing vector and cre-dependent adeno-associated viruses (AAVs) anterograde tracing vector, combined with a transgenic VGAT-IRES-Cre mice, to map the inputs and outputs of VN GABAergic neurons in the whole brain. We found that 51 discrete brain regions received projections from VN GABAergic neurons in the whole brain, and there were 77 upstream nuclei innervating GABAergic neurons in the VN. These nuclei were mainly located in four brain regions, including the medulla, pons, midbrain, and cerebellum. Among them, VN GABAergic neurons established neural circuits with some functional nuclei in the whole brain, especially regulating balance maintenance, emotion control, pain processing, sleep and circadian rhythm regulation, and fluid homeostasis. Therefore, this study deepens a comprehensive understanding of the whole-brain neural connectivity of VN, providing the neuroanatomical information for further research on the neural mechanism of the co-morbidities with vestibular dysfunction.

[Peripheral nervous impairment in a patient with methylmalonic aciduria combined with hyperhomocysteinemia].

Methylmalonic aciduria combined homocysteinemia can cause multisystemic damages, mainly involving central nervous system, while the peripheral nerves are rarely impaired. A 10-year-old boy complained of weakness of both lower extremities for 1 month. His past history showed mildly delay of intelligence as well as motor development. He had proteinuria when he was 3 years old and was diagnosed as epilepsy, which was controlled by sodium valproate when he was 8 years 6 months old. His physical examination showed attenuated bilateral knee jerk reflex, while the bilateral achilles tendon reflex was absent; the examination of sensation was normal and the bilateral Babinski sign was positive. The electromyography indicated injury of peripheral nerves. The elevated levels of urine methylmalonic aciduria and plasma homocysteinemia were consistent with the diagnosis of methylmalonic aciduria combined homocysteinemia. The pathogenic gene was confirmed as MMACHC, on which two pathogenic mutations (c.365A>T and c.609G>A) were detected. cblC defect was confirmed. He was treated by vitamin B12, calcium folinate, L-carnitine and betaine supplementation, and significant improvement was observed after 6 months. According to this case, we suggest that urinary organic acid analysis and plasma homocysteine should be performed in patients with unknown peripheral neuropathy, especially combined with multisystemic damages.Early diagnosis and treatment are important to improve the prognosis.