Presence of S-100 beta in cholinergic neurones of the rat hindbrain.

The double staining of S-100 beta and choline acetyltransferase (ChAT) revealed that S-100 beta immunoreactivity was localized in most, but not in all, cholinergic neurones in the somatomotor nuclei of the cranial nerves and in the ambiguus nucleus. S-100 beta was present in almost all cholinergic neurones in the brain stem reticular, red, vestibular (excluding medial), mesencephalic trigeminal and cerebellar nuclei. However, S-100 beta immunoreactivity was lacking in cholinergic neurones in the parabrachial complex, the dorsal motor nucleus of the vagal nerve and most sensory nuclei. No S-100 beta-positive neurones lacked ChAT immunoreactivity. Taken together with the fact that the vulnerability of motoneurones to axotomy is markedly reduced in the first 3 postnatal weeks, during which period neuronal S-100 beta appears and increases, a possible effect of S-100 beta on the survival of cholinergic motoneurones may be suggested.