Non-twitch muscle fibrs and proprioception in the extraocular muscles in mammals

• Applicant: Professorin Dr. Anja Horn-Bochtler
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2004 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5422501

A main finding of the last funding period was the localisation of the cell bodies of palisade endings (PE), which innervate the myotendinous junction of the extraocular muscles. In rhesus monkey the PE cell bodies were identified in the brainstem in the periphery of the motonuclei of extraocular muscles. Up to date these peripheral neurons have been considered as the motoneurons of multiply-innervated muscle fibres (MIF) representing a special tonic muscle fibre type unique to extraocular muscles in mammals. Preliminary data indicate that unlike the other nerve endings in the eye muscle the PEs contain the calcium binding protein calretinin. Aim in this last funding period addressing the proprioception of the extraocular muscle is a study of the connection between PEs and MIF motoneurons based on our new data. In 2 projects the following questions will be addressed: 1. Inhowfar do the PEs and the multiple nerve endings of the tonic muscle fibres represent two anatomically separate systems (sensory and motor) within a complex proprioceptive system? 2. Where are the PE cell bodies located in delineation from MIF-motoneurons and preganglionic neurons of the ciliary ganglion? Inhowfar do the PEs show histochemical alterations in strabismus and congenital nystagmus in humans. The finding of the selective association of the calcium-binding protein calretinin with premotor upgaze pathways is the basis for further investigations in rhesus monkey: 3. Do calretinin-positive afferents contact the upgaze motoneurons via excitatory or inhibitory synapses? Do they target cell bodies of the PEs and/or tonic MIFs?

• DFG Programme: Research Grants