1. Dopamine/BDNF loss underscores narcosis cognitive impairment in divers: a proof of concept in a dry condition
- Author
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Gerardo Bosco, Tommaso Antonio Giacon, Nazareno Paolocci, Alessandra Vezzoli, Cinzia Della Noce, Matteo Paganini, Jacopo Agrimi, Giacomo Garetto, Danilo Cialoni, Natalie D’Alessandro, Enrico M. Camporesi, and Simona Mrakic-Sposta
- Subjects
Decompression ,Deep diving ,Narcosis ,Brain-derived neurotrophic factor (BDNF) ,Dopamine ,Reactive oxygen species (ROS) ,Physiology ,Brain-Derived Neurotrophic Factor ,Diving ,Public Health, Environmental and Occupational Health ,General Medicine ,DDT ,Inert Gas Narcosis ,Glutamates ,Physiology (medical) ,Humans ,Cognitive Dysfunction ,Orthopedics and Sports Medicine ,Stupor ,Reactive Oxygen Species - Abstract
Purpose Divers can experience cognitive impairment due to inert gas narcosis (IGN) at depth. Brain-derived neurotrophic factor (BDNF) rules neuronal connectivity/metabolism to maintain cognitive function and protect tissues against oxidative stress (OxS). Dopamine and glutamate enhance BDNF bioavailability. Thus, we hypothesized that lower circulating BDNF levels (via lessened dopamine and/or glutamate release) underpin IGN in divers, while testing if BDNF loss is associated with increased OxS. Methods To mimic IGN, we administered a deep narcosis test via a dry dive test (DDT) at 48 msw in a multiplace hyperbaric chamber to six well-trained divers. We collected: (1) saliva samples before DDT (T0), 25 msw (descending, T1), 48 msw (depth, T2), 25 msw (ascending, T3), 10 min after decompression (T4) to dopamine and/or reactive oxygen species (ROS) levels; (2) blood and urine samples at T0 and T4 for OxS too. We administered cognitive tests at T0, T2, and re-evaluated the divers at T4. Results At 48 msw, all subjects experienced IGN, as revealed by the cognitive test failure. Dopamine and total antioxidant capacity (TAC) reached a nadir at T2 when ROS emission was maximal. At decompression (T4), a marked drop of BDNF/glutamate content was evidenced, coinciding with a persisting decline in dopamine and cognitive capacity. Conclusions Divers encounter IGN at – 48 msw, exhibiting a marked loss in circulating dopamine levels, likely accounting for BDNF-dependent impairment of mental capacity and heightened OxS. The decline in dopamine and BDNF appears to persist at decompression; thus, boosting dopamine/BDNF signaling via pharmacological or other intervention types might attenuate IGN in deep dives.
- Published
- 2023