MULTIPLE ORIGINS OF CEREBELLAR CHOLINERGIC AFFERENTS FROM THE LOWER BRAIN-STEM IN THE GERBIL

The possible origins of cerebellar cholinergic afferents from the lowe r brainstem of the gerbil were examined using immunohistochemistry com bined with retrograde neuronal labelling techniques. Choline acetyltra nsferase (ChAT) monoclonal antibody was used in conjunction with a ret rogradely transported tracer, horseradish peroxidase (HRP). The use of this technique allowed an unequivocal localisation of cholinergic neu rons in different parts of the lower brainstem projecting to the cereb ellum. In addition, single labelling of acetylcholinesterase (AChE), C hAT and HRP was carried out to elucidate the efferent projection from the lower brainstem to the cerebellum as well as the cholinergic distr ibution in these two areas. Our results showed the presence of HRP/ChA T double-labelled neurons in (1) the midline medulla: the periventricu lar gray beneath the 4th ventricle, C3 adrenergic area, raphe obscurus nucleus and medial longitudinal fasciculus, (2) the reticular formati on: the medullary, lateral, intermediate, gigantocellular, lateral par agigantocellular and dorsal paragigantocellular reticular nuclei and g igantocellular reticular nucleus ventralis, and (3) sensory;nuclei: th e gracile nucleus, cuneate nucleus, external cuneate nucleus, spinal t rigeminal nucleus interpolaris, prepositus hypoglossal nucleus and med ial vestibular nucleus. In the cerebellum, AChE-positive messy fibres were chiefly localised in the vermian lobules VIb,c, VII and X, parame dian lobule, crura I and II, paraflocculus and flocculus, and they wer e distributed in the white matter and granular layer of the cortex. Th e 3 above-mentioned cerebellar cholinergic afferent systems associated with the unique AChE distribution pattern in the cerebellum may be of important functional significance.