Quantitative study of the reticular-motor neuronal contacts in the spinal cord of the lampern

The number and location of contacts which are made by two HRP-labelled motoneurons with the individual Müller axons in lamprey was investigated. Each motoneuron had contacting zones with the ventromedial and ventrolateral Müller axons, but had no contacts with the dorsolateral Müller axon. The contacting zones which were extended for 0.5-27 microns were revealed on the motoneuron dendrites at a distance of 42-195 microns from the soma. Each motoneuron made 1 to 3 contacts with a single Müller axon. The specificity of the structure and function of reticular-motor neuronal connections in the spinal cord of lamprey is discussed.