Microcomputer use in measuring onset, duration, and recovery from nondepolarizing skeletal muscle relaxants in rabbits

This report describes a method which has been developed to use an Apple II Plus microcomputer in studies of the time course and dose response of potential skeletal muscle relaxant drugs. Rabbits are anesthetized with pentobarbital, tracheotomized, and the right common carotid artery is cannulated for direct measurement of blood pressure and heart rate. The ulnar nerve is stimulated at the elbow. Twitch, “train‐of‐four” (T4), tetanus, and posttetanic potentiation (PTP) are monitored by a force displacement transducer. These analog physiological signals are led from a polygraph through an lsaac Cyborg analog‐to‐digital converter attached to the microcomputer where they are stored in digital form. Each animal receives the test drug twice. Spontaneous recovery is allowed following the first administration while the second dose is reversed with neostigmine. The rate of onset, time and magnitude of maximal effect, time and rate of recovery, and time and magnitude of cardiovascular changes are all automatically calculated for both the control and the neostigmine reversal experimental phases. The effect of the test dose on each parameter is rated to provide a composite score for each dose of the test compound as the dose‐response series is completed. All parameters are plotted using a dot‐matrix printer and data are stored to disk. When doses, in 0.1‐log intervals, from the dose which produces no measurable effect to those doses producing unacceptably long durations, have been administrated, the computer uses the composite scores to report an optimal dose. Using regression analysis, the dose required to provide a 90% depression of twitch is calculated. This calculated dose is compared to equiefficacious doses of other test compounds. A tabular, graphic, and narrative report of the drug's effects is generated by the computer with comparison to other compounds of pctential interest. These programs and methods provide efficient data collection and data analysis. They provide for standard report generation. Finally, they allow for comparisons to be made among many pharmacologic parameters of many test compounds, thus providing understanding of the mechanisms of action of the test compounds.