Chronaxie in Morphine Addicted Rats on High and Low Calcium Diets

Abstract

Experiments by one of us (L. E. D.) have shown that the changes in water content of tissues and blood, and the characteristic symptoms accompanying morphine addiction and withdrawal in dogs and rats can be ameliorated by the use of a high calcium diet together with injections of “parathormone”. This suggests a parallel with parathyroid tetany. In this latter condition there is little change in the chronaxie of motor nerves, but a decided increase in the chronaxie of skeletal muscles; this high chronaxie is, however, reduced to the normal by administration of “parathormone.” To determine objectively, if possible, the difference in excitability of our rats on the calcium treatment and those not on the treatment, chronaximetric determinations were made. The composition of the diets was as follows: The rats were first addicted by daily injections of morphine sulphate in doses increasing from 20 mg. to 50 mg. per kilo body weight over an interval of 2 weeks. At the chosen time each rat was decerebrated under ether anaesthesia, one sciatic nerve being used for peripheral stimulation, the other for central stimulation, the chronaxie being determined every 15 minutes during the second hour after decerebration when the readings had become constant. Three rats were used as controls on each diet, and 3 morphinized rats for chronaxie measurements on the last day of addiction, and 3 for each of the 3 days following withdrawal. In the tables each result is the average of 3 individuals. Thus in Table I the value .11 for peripheral stimulation in the control group one hour after decerebration is the average of .11, .09, .14; the chronaxie of .12 for central stimulation is the average of .12, .12, .14; 2 hours after decerebration the value .09 is the average of .08, .08, .10 for peripheral stimulation and .08 is the average of .09, .06, .08 for central stimulation.