Projections from the superior colliculus to the trigeminal system and facial nucleus in the rat

Abstract

To determine the influence of the superior colliculus (SC) in orienting behaviors, we examined SC projections to the sensory trigeminal complex, the juxtatrigeminal region, and the facial motor nucleus in rats. Anterograde tracer experiments in the SC demonstrated predominantly contralateral colliculotrigeminal projections. Microinjections in the deep layers of the lateral portion showed labeled nerve fibers and terminals in the ventromedial parts of the caudal principal nucleus and of the rostral oral subnucleus and in the medial part of the interpolar subnucleus. Some terminals were also observed in the juxtatrigeminal region and in the dorsolateral part of the facial motor nucleus contralaterally, overlying the orbicularis oculi motoneuronal region. Verification by retrograde tracer injections into the trigeminal target regions showed labeled SC neurons mostly in lateral portions of layers 4-7. When the juxtatrigeminal region was involved, a remarkable increase of labeled neurons was observed, having a patch-like arrangement with a decreasing gradient from lateral to medial SC portions. Retrograde tracer injections in the dorsolateral VII nucleus showed bilateral labeled neurons mainly in the deep lateral SC portion. Retrograde BDA microinjections into the same trigeminal or juxtatrigeminal regions, followed by gold-HRP into the dorsolateral VII nucleus, demonstrated a significant number of SC neurons in deep layers 6-7 projecting to both structures by axon collaterals. These neurons are mediolaterally grouped in patches along the rostrocaudal SC extent; a subset of them are immunoreactive for glutamic acid decarboxylase (GAD). They could be involved in the coordination of facial movements. Simultaneous anterograde and retrograde tracer injections into the lateral SC portion and the VII nucleus respectively localized trigeminofacial neurons receiving collicular input in the trigeminal principal nucleus and pars oralis. Therefore the SC should play a crucial role in regulating motor programs of both eye and eyelid movements.

Descriptive and functional neuroanatomy of locus coeruleus-noradrenaline-containing neurons involvement in bradykinin-induced antinociception on principal sensory trigeminal nucleus

“…These findings are in harmony with previous studies, showing PAG-dorsal raphe nucleus connections and reciprocal connections between PAG and both the principal trigeminal nucleus and spinal trigeminal nucleus (Li et al, 1993a,b,c;Davergne et al, 2004). In addition, a previous report demonstrated that PAG neurons strongly innervate the rostromedial pericoerulear region, including Barrington's nucleus (Ennis et al, 1991).…”

Interrelationships between dental occlusion and plantar arch

“…Studies have revealed connections (in humans and in cats) between motor, mesencephalic, main and spinal nuclei of the trigeminus and vestibular and oculomotor nuclei (Pinganaud et al, 1999), dorsal and ventral horn of the cervical spinal cord (C1eC5) (Buisseret-Delmas and Buisseret, 1990), prepositus nucleus of the hypoglossus, cerebellum (Pinganaud et al, 1999), superior colliculus and many brainstem nuclei (nucleus of the solitary tract, dorsal reticular formation, cuneate nucleus) (Marfurt and Rajchert, 1991;Pompeiarto et al, 1992;Dauvergne et al, 2004). All the anatomical connections mentioned above suggest that portions of the trigeminal system strongly influence the coordination of posture.…”

The search space of the rat during whisking behavior

“…The centering of the vibrissal tips about the eyes may represent a peripheral correlate of the neural registration of the tactile and visual systems found in structures such as the superior colliculus (McHaffie and Stein, 1982;Dauvergne et al, 2004;Bezdudnaya and Castro-Alamancos, 2011). This geometric arrangement will inherently tend to ensure that tactile and visual modalities operate within the same coordinate system and bring tactile and visual maps into registration.…”