Morphometric evaluation of the neuroprotective effect of deprenyl on postaxotomic motor neuron losses.

Newborn rats were used to evaluate the neuroprotective effect of deprenyl on spinal motor neurons. The left sides were axotomized at age day 5 and the right sides were kept as a control. One hour after surgery, the operated animals received a daily dose of deprenyl intraperitoneally for 21 days. Each group received 0.25, 10, 30, 45, 60, or 75 mg/kg. The control side received the vehicle only. The number of motor neurons in the L4 through L6 spinal segments in all groups was counted, and the results were tested for normality using the Kolmogorov-Smirnov test. The number of the motor neurons at the axotomized treated sides were compared with those of the intact treated sides using analysis of variance. Significant differences (p < 0.05) were found in all groups except for the highest dose (75 mg/kg). The results in the untreated control showed a significant reduction in the percentage of motor neurons in the axotomized untreated group (-25.6%). The percentages of neuronal response and the percentages of maximal response were calculated, and the results show a sustained increase in percentage of neuronal response, with the highest response at a dose of 45 mg/kg followed by a decline. The results of the regression analysis show that there were two phases in the spinal motor neuron response: an initial neuroprotective phase followed by a neurotoxic declining phase. This study confirms the neuroprotectivity of motor neurons by deprenyl.