Abstract
The role of the upper brain upon the reflex response of the long ciliary nerve produced by stimulating the sciatic nerves was investigated, using the efferent impulses from a single or few active units of the long ciliary nerve in the cats.
1. In non-decerebrate cats a marked increased activity of the long ciliary nerve was elicited by stimulating the sciatic nerve centrally. Such a reflex activation was not affected with the removal of the cerebral cortex and the anterior half of the thalamus, whilst it was greatly reduced after the removal of the hypothalamus.
2. In decerebrate cats the responses in the sympathetic nerve to nociceptive stimuli were various; in some fibers a slightly increased activation was evoked, whereas in other fibers an inhibition of the spontaneous discharges was elicited irrespective of the frequency and strength of the stimuli. Such responses were also recognized in the medullary animal.
3. In spinal cats the excitatory response of the long ciliary nerve did not occur, whereas in some fibers inhibition of the spontaneous activity was produced with strong stimuli.
4. From these results it was highly probable that the interbrain particularly the hypothalamus, and the medulla oblongata played an important role for the development of the reflex activation of the long ciliary nerve. Furthermore, the reflex inhibition of the long ciliary nerve was discussed.
