THE FAILURE OF RESPIRATION IN DEATH BY TETRODOTOXIN POISONING

¹ Department of Physiology, University of Hong Kong, Hong Kong

After intravenous injection of tetrodotoxin in a dose which led to respiratory failure in the rat, the phrenic nerve continued to convey massive bursts of nerve impulses from the medullary centre for some time after cessation of respiratory movement, contraction of diaphragm and diaphragmatic muscle action potentials. In artificially ventilated intact rats the contractile response of a hemidiaphragm to indirect and direct stimulation diminished and disappeared together when tetrodotoxin was injected intravenously. In curarized rats, the response to direct stimulation disappeared when tetrodotoxin was given. In artificially ventilated rats which had one phrenic nerve cut 2 months previously, the contractile response of the denervated hemidiaphragm to direct stimulation and that of the intact opposite hemidiaphragm to indirect stimulation both diminished and stopped after the administration of tetrodotoxin. Action potentials were elicited from the biceps brachii muscle and its motor nerve following stimulation of the motor cortex; after injection of tetrodotoxin, both nerve and muscle action potentials diminished and disappeared together. It appears from the evidence presented that the failure of respiration in tetrodotoxin poisoning is due to paralysis of the respiratory muscles which were apparently more susceptible to the action of tetrodotoxin than the respiratory and other motor nerves or the non-respiratory striated muscles.

Note:

We are grateful to Professors E. J. Zaimis and P. G. Wright and Dr. Barbara Smith for advice and Miss Y. M. Cheung for careful technical assistance. This research was partly supported by grants from the China Medical Board of New York Inc. and the University of Hong Kong Committee on Research Grants.