Retrograde effects of axotomy on the intramedullary axon collateral systems and recurrent inhibitory reflexes of cat spinal motoneurones

The intramedullary axon collateral systems of adult cat spinal alpha-motoneurones were studied with morphological and physiological techniques 12 weeks after peripheral transection of the motor axons. Morphologically, intracellular horseradish peroxidase (HRP) staining showed that the axotomy induced an elimination of whole collateral trees from the proximal parts of the lesioned axons. The axon collateral systems that still remained in the axotomized neurones appeared quite normal. Physiologically, intracellular recordings failed to reveal a corresponding reduction in the amount of recurrent inhibition produced by the axotomized cells. Possible explanations for the discrepancy between the morphological and physiological results are discussed.