Present address: Department of Visual System Analysis, The Netherlands Ophthalmic Research Institute, Meibergdreef 9, NL-1100 AC Amsterdam, the Netherlands.
Characterization of a directional selective inhibitory input from the medial terminal nucleus to the pretectal nuclear complex in the rat
Article first published online: 25 DEC 2001
European Journal of Neuroscience
Volume 10, Issue 5, pages 1533–1543, May 1998
How to Cite
Schmidt, M., Van Der Togt, C., Wahle, P. and Hoffmann, K.-P. (1998), Characterization of a directional selective inhibitory input from the medial terminal nucleus to the pretectal nuclear complex in the rat. European Journal of Neuroscience, 10: 1533–1543. doi: 10.1046/j.1460-9568.1998.00161.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 24 July 1997, revised 1 December 1997, accepted 19 December 1997
- accessory optic system;
- electrical stimulation;
- retrograde tracing;
The receptive field properties of neurons in the medial terminal nucleus of the accessory optic system (MTN) that project to the ipsilateral nucleus of the optic tract (NOT) and dorsal terminal nucleus (DTN), as identified by antidromic electrical activation, were analysed in the anaesthetized rat. The great majority (88%) of MTN neurons that were antidromically activated from NOT and DTN preferred downward directed movement of large visual stimuli while the remaining cells preferred upward directed stimulus movement. Distinct retrograde tracer injections into the NOT/DTN and the ipsilateral inferior olive (IO) revealed that no MTN neurons project to both targets. MTN neurons projecting to the ipsilateral NOT/DTN were predominantly found in the ventral part of the MTN, whereas those projecting to the IO were found in the dorsal part of the MTN. In situ hybridization for glutamic acid decarboxylase (GAD) mRNA was used as a marker for GABAergic neurons. Up to 98% of MTN neurons retrogradely labelled from the ipsilateral NOT/DTN also expressed GAD mRNA. Earlier studies have shown that MTN neurons that prefer upward directed stimulus movements are segregated from MTN neurons that prefer downward directed stimulus movements. It also has been demonstrated that directionally selective neurons in the NOT/DTN prefer horizontal stimulus movements and receive an inhibitory input from ipsilateral MTN. Our results indicate that this input is mediated by GABAergic cells in the ventral part of MTN, which to a large extent prefer downward directed stimulus movements, and that the great majority of MTN neurons that prefer upward directed stimulus movements project to other targets one of which possibly is the IO.