抄録
What kind of a role does the snout sensory input play in the feeding activity in animals? In order to obtain the neuroanatomical information on this question, the following study was conducted on 21 dd mice including 3 young mice, 14 young Wistar rats and 6 adult Japanese shrew moles.
The animals were subjected to unilateral and bilateral infraorbital nerve transection. Transganglionic degeneration was studied by the Nauta method and electron microscopy which included non-HRP and HRP application to the neck muscles.
Transganglionic degeneration was found in every experimental case. In the mouse, it spread from the brain stem to the upper part of the thoracic spinal cord. At the obex level, transganglionically degenerated fibers appeared dorsal to the cuneate nucleus on each side and then descended to the posterior funiculi of the cervical spinal cord. The degenerated fibers entered the posterior and anterior horns at each segment and reached as far as the level of the first thoracic spinal cord. Synaptic boutons of the transganglionically degenerated axons terminated in the motor nerve cells. In the rat, the degeneration pattern resembled that of the mouse in the brain stem but not at the spinal cord level.
Under electron microscopy, in the three species of animals, at the various levels of the cervical spinal cord, transganglionically degenerated axons and axo-dendritic and axo-axonic synapses were discovered in the posterior horn and besides these two synapse types the axo-somatic synapses were also found bilaterally in the anterior horn.
