Connections between the trigeminal mesencephalic nucleus and the superior colliculus in the rat

Retrograde tracing methods are employed here to demonstrate that neurons in the trigeminal mesencephalic nucleus (5me) project to the superior collicu lus (SC) in the rat. These neurons, mainly of small size, are situated bila terally in the caudal part of the nucleus. Anterograde tracing studies demo nstrated the existence of SC projections to neurons in 5me. The SC fibers c ontact 'en passant' small as well as large cell bodies of 5me neurons. Thes e pathways suggested a role of the 5me neurons in oculomotor control and as sociated ore-facial functions. (C) 2000 Elsevier Science Ireland Ltd. All r ights reserved.