DRUGS THAT INCREASE GAMMA-AMINOBUTYRIC ACID TRANSMISSION PROTECT AGAINST THE HIGH-PRESSURE NEUROLOGICAL SYNDROME

The effects on the high pressure neurological syndrome (HPNS) of drugs which facilitate GABA transmission were investigated. Threshold pressures of the onset of the behavioral signs of the HPNS in mice, tremors and convulsions, were established. Flurazepam hydrochloride 20 and 10 mg/kg and sodium valproate 800 and 400 mg/kg substantially raised the threshold pressures for both tremor and convulsions. Amino-oxyacetic acid 35 and 25 mg/kg and diaminobutyric acid 600 mg/kg also significantly increased the thresholds. Muscimol 1 mg/kg (and 150 ng i.c.v. [intracerebroventricularly]) was ineffective at nontoxic doses. These effects paralleled the drugs'' ability to raise the convulsion threshold to i.v. infusion of bicuculline in mice. Drugs with actions more selective than those of the general anesthetics are effective against the HPNS. There may be GABAergic component to the effects of general anesthetics on the HPNS. [These compounds may be useful against the HPNS of deep sea diving.].