High pressure neurologic syndrome type 2 seizure in mice

Progressive compression in helium/oxygen (heliox) atmospheres elicits in mice and many other vertebrates tested a complex series of effects known as the high pressure neurologic syndrome (HPNS). The most dramatic behavioral manifestations of the syndrome are two successive and distinct convulsive seizures. HPNS type 1 and type 2. In the present study, a maximum likelihood estimation procedure was applied to 11 models of inheritance of the difference in the time elapsed until manifestation of the type 2 seizure in heliox-compressed C57BL/6 and BALB/c mouse strains, their F1 hybrid, and the backcross generations. The "preferred" model specifying interaction between two major unlinked autosomal loci was confirmed indirectly by further breeding tests. The tests also showed that type 1 and type 2 seizure thresholds are uncorrelated but type 1 always preceded type 2. A challenge to the latter result involving mating backcross mice with high type 1 and type 2 seizure thresholds to mice with low type 1 and type 2 seizure thresholds produced no instance of alteration of the seizure order.