Position sensitivity of de-efferented muscle spindles in experimental acrylamide neuropathy.

An experimental neuropathy was induced in cats by injections of acrylamide (7.5, 15 or 30 mg/kg/day) for 2 to 10 days. The responses of primary and secondary endings of soleus muscle spindles to stretch were evaluated and correlated with the appearance of ataxia and incoordinated motor movements. Animals that received 15 or 30 mg/kg/day became ataxic and demonstrated poor motor coordination on the 7th or 4th day, respectively. At these times, both primary and secondary endings of muscle spindles had elevated thresholds and diminished discharge frequencies. Continued acrylamide administration resulted in exacerbation of the clinical symptoms and further attenuation of spindle responses. The discontinuation of acrylamide was followed by slow recovery. Only those cats which received a total dose of 75 mg/kg or less remained asymptomatic and had normal spindle function. The coincidence of onset of motor coordination deficits and spindle dysfunction, coupled with a lack of demonstrable motor defect at the same time, suggests that the initial clinical features of acrylamide neuropathy may be partly the consequence of impaired spindle function.