Nitrogen narcosis is a neurological syndrome that manifests when humans or animals encounter hyperbaric nitrogen, resulting in a range of motor, emotional, and cognitive abnormalities. The anterior cingulate cortex (ACC) is known for its significant involvement in regulating motivation, cognition, and action. However, its specific contribution to nitrogen narcosis-induced hyperlocomotion and the underlying mechanisms remain poorly understood. Here we report that exposure to hyperbaric nitrogen notably increased the locomotor activity of mice in a pressure-dependent manner. Concurrently, this exposure induced heightened activation among neurons in both the ACC and dorsal medial striatum (DMS). Notably, chemogenetic inhibition of ACC neurons effectively suppressed hyperlocomotion. Conversely, chemogenetic excitation lowered the hyperbaric pressure threshold required to induce hyperlocomotion. Moreover, both chemogenetic inhibition and genetic ablation of activity-dependent neurons within the ACC reduced the hyperlocomotion. Further investigation revealed that ACC neurons project to the DMS, and chemogenetic inhibition of ACC-DMS projections resulted in a reduction in hyperlocomotion. Finally, nitrogen narcosis led to an increase in local field potentials in the theta frequency band and a decrease in the alpha frequency band in both the ACC and DMS. These results collectively suggest that excitatory neurons within the ACC, along with their projections to the DMS, play a pivotal role in regulating the hyperlocomotion induced by exposure to hyperbaric nitrogen.
Animals ; Gyrus Cinguli/drug effects* ; Male ; Mice, Inbred C57BL ; Locomotion/drug effects* ; Neurons/drug effects* ; Mice ; Nitrogen/toxicity* ; Inert Gas Narcosis/physiopathology* ; Corpus Striatum/physiopathology*

The popularity of SCUBA diving as aquatic sports is increasing in trend and therefore the risk of diving-related accidents or death is also increased. In underwater environment, with its rapidly changing ambient pressures, human body is subjected to pathophysiologic challenges. The common forms of medical problem with diving are barotrauma, decompression sickness and nitrogen narcosis, and the most common cause of diving-related death is drowning. However, the determination of the cause of death associated with diving should not be derived from the autopsy alone but must result from interpretation of data including a detailed history of the events prior to death, information about accident locus, diving suits, breathing apparatus and their accessories, and complete autopsy including toxicology and histological examination. And to explain the mechanism of death, the forensic pathologists should understand the diving physiology, law of gas physics and other diving hazards, and also be approached by the team effort involved by professional diver. Through the review of cases of SCUBA diving-related death and the literature, the author discuss the investigative approach to diving accidents and complete autopsy procedure with toxicological screen.
Autopsy ; Barotrauma ; Cause of Death ; Decompression Sickness ; Diving ; Drowning ; Human Body ; Inert Gas Narcosis ; Jurisprudence ; Physiology ; Respiration ; Sports ; Toxicology