Assessment of chemically-induced changes in the neuromuscular function of rats using a new recording grip meter

The effects of several psychoactive drugs on the grip strength of rats were evaluated by a new recording grip meter technique that provides graded or continuous data. The same subjects were also tested by an inclined screen procedure, which yields quantal or all-or-none data. The lowest doses (lowest effective dose; LED) required to produce a significant decrease in grip meter scores by chlorpromazine (CPZ), chlordiazepoxide (CDZ), and phenobarbital (PHEN) were 5, 9, and 20 mg/kg respectively. $\text{d}$-Amphetamine (0.5– 8 mg/kg) resulted in a significant, dose-related increase in grip meter scores. The LEDs for CPZ and PHEN using the inclined screen test were 10 and 40 mg/kg, respectively. These values are 2 times the corresponding figures obtained in the grip meter test. The LED for chlordiazepoxide was 9 mg/kg in the inclined screen, which is the same as that in the grip meter test, while $\text{d}$-amphetamine had no effect on neuromuscular function measured by the inclined screen.The results of these experiments indicate that the grip method is a useful technique capable of measuring both increases and decreases in the grip strength of rats. Relative to the inclined screen procedure, which measures a combination of factors, the grip meter technique appears to be a sensitive procedure capable of measuring forelimb grip strength selectively.