Anesthesia with
diethyl ether significantly alters the course and outcome of experimental
infections with the
equine encephalomyelitis virus (Eastern or Western type) or with the St. Louis encephalitis virus. No comparable effect is observed in experimental
infections produced with
rabies or
poliomyelitis (Lansing) viruses. The neurotropic
virus infections altered by
ether anesthesia are those caused by viruses which are destroyed in vitro by this
anesthetic, and those
infections not affected by
ether anesthesia are caused by viruses which apparently are not destroyed by
ether in vitro. Another striking difference between these two groups of viruses is their pathogenesis in the animal host; those which are inhibited in vivo by
ether anesthesia tend to infect cells of the cortex, basal ganglia, and only occasionally the cervical region of the cord. On the other hand, those which are not inhibited in vivo by
ether anesthesia tend to involve cells of the lower central nervous system and in the case of
rabies, peripheral nerves. This difference is of considerable importance in view of the fact that
anesthetics affect cells of the lower central nervous system only in very high concentrations. It is obvious from the complexity of the problem that no clear-cut statement can be made at this point as to the mechanism of the observed effect of
ether anesthesia in reducing the mortality rate in certain of the experimental neurotropic
virus infections. Important possibilities include a direct specific effect of
diethyl ether upon the virus and a less direct effect of the
anesthetic upon the virus through its alteration of the metabolism of the host cell.