Recovery of central respiratory function following anticholinesterase intoxication

Spontaneous recovery of central respiratory function was studied in anesthetized guinea pigs intoxicated with pinacolyl methylphosphonofluoridate (Soman) or isopropyl methylphosphonofluoridate (Sarin). I.v adiministration of either agent produced an immediate disruption phrenic nerve activiity and resulting ventilatory failure. Animals were maintained on artifical respiration until spontaneous functional recovery was complete, as evidenced by the re-establishment of synchronized burst activity on the phrenic nerve and return of tracheal airflow. This usually occurred within 1 h. Animals were sacrificed at predetermined intervals after intoxication, and the brainstem homogenates were analyzed for AChE activity. Results showed no significant return of AChE activity after 1 h, although functional recovery of respiration was complete within this time. Additional doses of the agents were administered at various times after recovery from the respiratory blockade. Following spontaneous restoration of ventilatory function, subsequent injections of the organophosphorus compounds failed to reinstate central respiratory paralysis, although they further depressed brainstem AChE levels. These data suggest that spontaneous recovery of central respiratory function after intoxication with Soman or Sarin may not be related to the return of AChE activity.