BARBITURATE-STRYCHNINE ANTAGONISM IN THE SPINAL CAT A QUANTITATIVE STUDY

¹ Department of Physiology, School of Medicine, University of Texas, Galveston

A method is described by which the flexion reflex in the spinal cat may be used over many hours as a delicate quantitative indicator of the effect on the spinal cord of such drugs as the barbiturates and strychnine.

An essential feature of the method is the use of a liquid electrode on the sensory nerve stimulated. A simple form which has been successfully used is described.

When this electrode is used and no drug is given, it can be shown that the flexion reflex threshold may increase only 2 to 4 Z-units over a period as long as 6 hours.

The barbiturates in contrast promptly raise the threshold, the amount depending on the dose and the barbiturate used.

Curves are given showing how the method brings out the characteristic differences between such barbiturates as luminal and evipal over a period of hours.

When the reflex remains high because of a barbiturate injection, strychnine lowers it—partially with a single dose, more completely with repeated doses—in most cases returning the threshold to its original level.

When the reflex threshold in the undrugged animal has risen slightly over a period of hours, the threshold may be lowered by strychnine as in the barbiturate experiments,—partially by single doses, more completely by repeated doses,—and sometimes to the original level.

Although the method described employs a calibrated coil and a primary current of known value, it is shown that records of accuracy and value may be obtained by using an ordinary small induction coil (Harvard Apparatus Company type) and an unknown primary current provided a mercury key and the special liquid electrode are used.