title: Sources of calretinin inputs to motoneurons of extraocular muscles involved in upgaze.
abstract: Recent monkey studies showed that motoneurons of the oculomotor nucleus involved in upward eye movements receive a selective input from afferents containing calretinin (CR). Here, we investigated the sources of these CR-positive afferents. After injections of tract-tracers into the oculomotor nucleus (nIII) of two monkeys, the retrograde labeling was combined with CR-immunofluorescence in frozen brainstem sections. Three sources of CR inputs to nIII were found: the rostral interstitial nucleus of the medial longitudinal fascicle (RIMLF), the interstitial nucleus of Cajal, and the y-group. CR is not present in all premotor upward-moving pathways. The excitatory secondary vestibulo-ocular neurons in the magnocellular part of the medial vestibular nuclei contained nonphosphorylated neurofilaments, but no CR, and they received a strong supply of large CR-positive boutons. In conclusion, the present study presents evidence that only specific premotor pathways for upward eye movements--excitatory upgaze pathways--contain CR, but not the up vestibulo-ocular reflex pathways. This property may help to differentiate between premotor up- and downgaze pathways in correlative clinico-anatomical studies in humans.
authors.affiliation: Institute of Anatomy I, Ludwig-Maximilians University of Munich, Munich, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Ahlfeld
authors.forename: Michael
authors.initials: M
authors.lastname: Mustari
authors.forename: Anja K E
authors.initials: AK
authors.lastname: Horn
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001933:Brain Stem / Q000033:anatomy & histology / Q000502:physiology; D064032:Calbindin 2; D002772:Cholera Toxin / Q000493:pharmacokinetics; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D008253:Macaca mulatta; D009046:Motor Neurons / Q000378:metabolism*; D009801:Oculomotor Muscles / Q000294:innervation* / Q000502:physiology; D009802:Oculomotor Nerve / Q000378:metabolism; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D014795:Visual Pathways / Q000502:physiology; D014909:Wheat Germ Agglutinins / Q000493:pharmacokinetics
chemical_list: C576764:CALB2 protein, human; D064032:Calbindin 2; D064030:S100 Calcium Binding Protein G; D014909:Wheat Germ Agglutinins; D002772:Cholera Toxin