Hyperbaric pressure effects on voltage-dependent Ca⁺² channels: Relevance to HPNS

Known, and unpublished data regarding hyperbaric pressure (HP) effects on voltage dependent-Ca²⁺ channels (VDCCs) were reviewed in an attempt to elucidate their role in the development of highpressure neurological syndrome (HPNS). Most postulated effects from studies performed in the last two decades (e.g., depressed maximal current) rely on indirect findings, derived from extracellular [Ca²⁺] manipulation or by observing Ca ²⁺-dependent processes. More recent experiments have tried to directly measure Ca²⁺ currents under high pressure conditions, some of which are potentially challenging previous indirect findings on one hand, but support findings from work done on neuronal behavior on the other. Additional support for some of the recent findings is provided by computer simulation of pressure effects on a spinal motor neuron activity. HP effect on different types of VDCCs seems to be selective - i.e., HP may suppress, facilitate or not change their activity. Thus, the specific distribution of the various types of the channels in each synaptic terminal or throughout the neuron will determine their function and will influence the neuronal network behavior under HP. Further research is needed in order to fully understand the HPNS etiology.