Presence of S-100β in cholinergic neurones of the rat hindbrain

THE double staining of S-100p and choline acetyltrans-ferase (aChAT) revealed that S-100P 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-100β was present in almost all cholinergic neurones in the brain stem reticular, red, vestibular (excluding medial), mesencephalic trigeminal and cerebellar nuclei. However, S-100β immunoreactivity was lacking in cholinergic neurones in the parabrachial complex, the dorsal motor nucleus of the vagal nerve and most sensory nuclei. No S-100β-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-100β appears and increases, a possible effect of S-100β on the survival of cholinergic motoneurones may be suggested.