Retraction and Expansion of the Dendritic Tree of Motor Neurones of Adult Rats induced in vivo

Cerf and Chacko 1 found that the number and diameter of motor neurone dendrites decreased after axotomy in the adult bullfrog. The purposes of the investigation reported here are to confirm and extend these observations in a mammal, to determine whether the dendritic changes are due to loss of axoplasm or loss of effective neuromuscular transmission, to see if dendrites recover after nerve regeneration has restored contact between the nerve and the originally innervated muscle mass, and if they recover after the regenerating nerve makes contact with different denervated muscle. Quantitative assessments of the dendritic spread of developing rat and human cortical neurones have been made by Eayrs and Goodhead 2 , and Schadé and van Groenigen 3 . Schapiro and Vukovitch 4 found that the number of dendritic spines of rat cortical neurones could be influenced by variety of experience during development; Jones and Thomas 5 and Matthews and Powell 6 reported a decrease in the number and length of dendrites after deafferentation. Possible neuronal plasticity in the central nervous system of adult rats has been reported by Raisman 7 .