THE ACTION OF SODIUM 4-HYDROXYBUTYRATE ON SPINAL REFLEXES.

The actions of sodium 4-hydroxybutyrate, gamma-aminobutyric acid and meprobamate have been studied in unanaesthetized animals, in local anaesthetic tests, on isolated organ preparations, on convulsions induced by picrotoxin and strychnine, and on monosynaptic (patellar) and polysynaptic (plantar) reflexes of the spinal cord. Sodium 4-hydroxybutyrate induced a sleep-like state with three unusual features: the righting reflex was remarkably persistent, respiration was good throughout and recovery was abrupt. gamma-Aminobutyric acid was inactive and meprobamate caused flaccid paralysis with loss of the righting reflex. None of the agents affected the responses of the rat diaphragm either to direct stimulation of the muscle or to indirect stimulation through the phrenic nerve. Only meprobamate reduced the responses of theguinea-pig isolated ileum preparation, showed local anaesthetic action and had an anticonvulsant action. All three compounds were capable, after intravenous or topical application, of blocking plantar reflexes in doses which did not affect the patellar reflex. The spinal animal responded in the same way, to the same dose of sodium 4-hydroxybutyrate, as the decerebrate preparation. Topical application to the motor cortex had no effect on spinal reflexes. We conclude that sodium 4-hydroxybutyrate acts preferentially on the internuncial neurones in the spinal cord but differs from meprobamate in its other actions. The similarity between the actions of sodium 4-hydroxybutyrate and of gamma-aminobutyric acid provides furtherevidence in support of the hypothesis that sodium 4-hydroxybutyrate is involved in the gamma-aminobutyric acid metabolic pathways.