The motor functional recovery after sciatic nerve crush was measured in rats treated with daily
injections of (a)
thyrotropin-releasing hormone (2.0 mg/kg, (b)
alpha-melanocyte-stimulating hormone (0.07 mg/kg/48 h), or (c)
testosterone propionate (4.4 mg/kg). The recovery of the motor function of the sciatic nerve was indicated by using the return of the toe-spreading response. None of the treatments differed significantly from saline controls in the time needed for recovery. The same procedure (without
injections) was carried out with castrated and noncastrated male rats in order to test the effect of the lack of
testosterone on recovery time after sciatic crush. The groups did not differ significantly as to their recovery times. The same method was used to study the effect of
spermine (10.0 mg/kg/day) on the recovery of motor function.
Spermine seemed to reduce the time needed for recovery from a mean value of 15.7 to 11.0 days (P less than 0.01). We also studied the effect of daily
injections of
spermine (13.0 mg/kg) on the sensory division of the peripheral nerve using the foot-flick test. The time needed for recovery after crush in the sciatic notch was reduced from 13.7 to 7.7 days (P less than 0.005). These results do not support the hypothesis that alpha-melantocyte-stimulating
hormone,
thyrotropin-releasing hormone, or
testosterone enhance functional recovery of severed motor axons. Our results confirm a previous observation that
spermine reduces the time needed for recovery after
trauma in peripheral motor neurons. The result of the foot-flick test suggests that
spermine enhances both motor and sensory recovery.