Distribution and peculiarities of axon collateral branching of rubro-spinal neurones in brainstem structures

Peculiarities of axon branching and distribution of rubro-spinal neurones in various brainstem stuctures were studied in acute cats using the technique of intracellular recording of antidromic action potentials as well as collision testing. Axon collaterals of rubro-spinal neurones into the main sensory trigeminal nucleus, facial nerve nucleus, descending (inferior) vestibular nucleus, lateral reticular nucleus, external cuneate nucleus, gracile and main cuneate nuclei were identified. Correlation between the antidromic impulse conduction time along the stem axon before and after collateral branching and the time of impulse conduction in the collaterals themselves was analysed. The number of axon collaterals of individual rubro-spinal neurones to particular brainstem structures was studied. A tendency was observed for the synchronous arrival of rubro-spinal impulses to various brainstem centres, due to an increase in conductance velocity the further away these centres were from the red nucleus.