The facial nucleus of the rat: Representation of facial muscles revealed by retrograde transport of horseradish peroxidase

Abstract

The representation of facial muscle groups in the facial nucleus of rat was examined by retrograde transport of HRP. Motoneurons supplying muscle groups are arranged in longitudinal columns. Those supplying nasolabial muscles are located in the lateral and ventral intermediate segments, posterior auricular muscles in a medial column, platysma in a n intermediate column; the lower lip and ocular muscles are in the ventral and dorsal segments respectively of the intermediate column. The posterior belly of the digastric muscle is supplied by motoneurons extending from the dorsal aspect of the facial nucleus to the caudal pole of the trigeminal motor nucleus.Several techniques have been employed to determine the central organization of the facial nucleus in a variety of species. These include chromatolysis (Marinesco, 1899; Van Gehuchten, 1898;Yagita, 1910;Papez, 1927;Vraa-Jensen, 1942), the Gudden method (Courville, 1966) loss of cholinesterase in the nucleus (Dom et al., 19731, and application of peroxidase to nerve stumps (Provis, 1977). All of these methods require section of peripheral nerves, although more than one peripheral facial nerve branch has been shown to supply some muscles (Provis, 1977). In addition, recent studies have cut adjacent nerves to avoid their uptake of protein tracer (Kume et al., 19781, or prepared only some facial nerve branches to avoid current spread from stimulation Martin and Lodge, 1977). These methods may have imposed an artificial organization on the nucleus. Similarly, the placement of lesions in parts of the facial nucleus with subsequent examination of individual muscles for evidence of degenerating motor end plates (Szentagothai, 1948) imposes restrictions upon the information that has been obtained. It is therefore not surprising that 3-6 anatomical subdivisions of the nucleus described from coronal Nissl-stained sections (Marinesco, 1899; Van Gehuchten, 1898;Yagita, 1910;Papez, 1927;Hogg, 1928;Nishi, 1965; Courville, 1966) have been related to peripheral branches of the facial nerve rather than to individual muscles or muscle groups.This study was undertaken to map the representation of muscle groups in the facial nucleus of the rat by retrograde transport of horseradish peroxidase (HRP) after its injection into individual facial muscle groups. It was a n essential prerequisite to tracing of central connections of the facia1 nucleus because afferents have been shown to terminate preferentially within the facial nucleus from the red nucleus (Courville, 1966;Martin and Dom, 1970;Mizuno and Nakamura, 1971;Yu et al., 1972;Edwards, 1972), the trigeminal nerve Stewart and King, 1963; Erzulumulu and Killackey, 19791, the hypoglossal nerve (Tanaka et al., 19711, and from respiratory centers (Sherrey and Megirian, 1977). Conflicting maps of the representation of muscles within the facial nucleus render the significance of these inputs unclear. MATERIALS AND METHODSThirty 250-g female hooded rats (Wistar strain) were given injections of 1-5 p1 of a 50% solution of HRP ...

Distribution of motoneurons supplying feline neck muscles taking origin from the shoulder girdle

“…It has also been observed in the fifth cranial nucleus, which contains the motoneurons of different jaw muscles (Batini et al, 1976;Terashima et al, 1994), in the oculomotor nuclei (Porter et al, 1983), in the facial nucleus (Courville, 1966;Dom, 1982;Hinrichsen and Watson, 1984), and in the hypoglossal nucleus, which supplies different muscles of the tongue (Krammer et al, 1979). When considering the functional significance of such close lamination, it is important to remember that the dendritic trees attached to the cell bodies of SAN motoneurons branch widely throughout much of the ventral horn (Vanner and Rose, 1984).…”

Expression of ghrelin receptor mRNA in the rat and the mouse brain

“…These subdivisions include three main ones (medial, intermediate and lateral), each of which contains about 30% of the facial motoneurons, as well as a fourth (dorsal cap) that contains about 10% of the neurons and a fifth, much smaller group of neurons (suprafacial nucleus) that lies dorsally (Ashwell, 1982;Friauf and Herbert, 1985;Hinrichsen and Watson, 1984;Komiyama et al, 1984;Martin and Lodge, 1977;Watson et al, 1982). Importantly, a wellestablished musculotopic organization within the facial motor nucleus subdivisions exists for many species, including the rat and mouse, in which the anteroposterior axis of the face is projected lateromedially on the facial motor nucleus (Ashwell, 1982;Friauf and Herbert, 1985;Hinrichsen and Watson, 1984;Komiyama et al, 1984;Martin and Lodge, 1977;Watson et al, 1982). As such, the soma of motoneurons controlling nasolabial muscles are located in the lateral subdivision, while those innervating perioral, orbital and neck muscles are in the intermediate subdivision and those innervating the external ear are in the medial subdivision.…”

Urocortin Expression in Rat Brain: Evidence Against a Pervasive Relationship of Urocortin-Containing Projections With Targets Bearing Type 2 CRF Receptors

“…UCN-ir projections are seen to this and other pretectal structures, as well as the oculomotor nuclei. Finally, the spinal trigeminal complex receives primary afferents from the anterior chamber of the eye (Panneton and Burton, 1981) and projects to the facial motor nucleus Klooster et al, 1993), aspects of which supply the eyelid musculature (Hinrichsen and Watson, 1984), defining substrates for a component of the corneal blink reflex. As noted (Klooster et al, 1993) EW, as well as UCN-ir, projections are in a position to modulate both central components of this reflex.…”