Primary and secondary sensory trigeminal projections in a cyprinid teleost, carp (Cyprinus carpio)

Primary and secondary sensory trigeminal projections were studied by means of tract-tracing methods in a cyprinid teleost, the carp. Tracer injections into the trigeminal nerve root labeled terminals in the ipsilateral principal sensory trigeminal nucleus, descending trigeminal nucleus, medial funicular nucleus, facial lobe, and medial part of posterior lateral valvular nucleus. The principal sensory trigeminal nucleus is considered a major origin of the secondary sensory trigeminal projections in teleosts. To investigate the secondary sensory trigeminal projections, tracer injections were performed into the principal sensory trigeminal nucleus. The present study suggests that the principal sensory trigeminal nucleus projects to the bilateral ventromedial thalamic nucleus, periventricular pretectal nucleus, stratum album centrale of the optic tectum, caudomedial region of lateral preglomerular nucleus, ventrolateral nucleus of semicircular torus, medial part of rostral and posterior lateral valvular nucleus, oculomotor nucleus, trochlear nucleus, trigeminal motor nucleus, facial motor nucleus, superior and inferior reticular formation, descending trigeminal nucleus, medial funicular nucleus, inferior olive, and to the contralateral sensory trigeminal nucleus. These observations indicate that the primary and secondary trigeminal sensory projections of a cyprinid teleost, the carp, are similar to those in percomorph teleosts. J. Comp. Neurol. 499:626–644, 2006. © 2006 Wiley-Liss, Inc.