Central projections of cervical primary afferent fibers in the guinea pig: An HRP and WGA/HRP tracer study

Abstract

The central course and the projections of the first and the second cervical dorsal root ganglia and of suboccipital muscle primary afferent fibers in the guinea pig were studied by means of anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA/HRP) or aqueous solution of horseradish peroxidase (HRP). Injections of WGA/HRP into the second cervical dorsal root ganglion produced labeling in the dorsal and ventral horns. Within the spinal cord, the largest amount of HRP reaction product was found within the lateral third of the substantia gelatinosa and within the central cervical nucleus. The main area of termination in the medulla was the external cuneate nucleus. However, HRP reaction product was also found within the medial and inferior vestibular nuclei, cell group x, the perihypoglossal nuclei, the nucleus of the solitary tract, and the nucleus of the spinal trigeminal tract. Descending fibers could be detected as caudal as spinal segment T5. Injections of WGA/HRP into the first cervical dorsal root ganglion produced heavy terminal label within the central cervical nucleus but not within the substantia gelatinosa. Again, the external cuneate nucleus was the main area of termination within the medulla. Label could not be observed within the vestibular nuclear complex or within the spinal trigeminal nucleus. Injections of aqueous HRP into the suboccipital muscles produced heavy transganglionic label within the central cervical nucleus, whereas the substantia gelatinosa totally lacked terminal label. Ascending proprioceptive fibers reached the external cuneate nucleus and group x. Scanty projections could be detected within the vestibular nuclei as well as within the perihypoglossal nuclei except for the nucleus prepositus hypoglossi. Label was absent in the spinal trigeminal nucleus.

Spinal afferents to functionally distinct periaqueductal gray columns in the rat: An anterograde and retrograde tracing study

“…With respect to these findings of a partial topographical separation of vlPAG-projecting and lPAG-projecting neurons within the UCC, a notable feature of deep neck muscle spinal afferents, as revealed by anterograde tracing studies in rat and cat, is a dense terminal field restricted to the intermediate and ventral gray of C1-C4 (Abrahams et al, 1979(Abrahams et al, , 1984aMysicka and Zenker, 1981;Ammann et al, 1983;Pfaller and Arvidsson 1988;Abrahams, 1989;Prihoda et al, 1991). Electrophysiological studies in the cat indicate that many of these deep neck muscle afferents are nociceptively driven (Abrahams, 1981(Abrahams, , 1989Abrahams et al, 1984a,b;Chudler et al, 1991;Yezierski and Broton, 1991;Yezierski, 1991).…”

The Neurochemically Diverse Intermedius Nucleus of the Medulla as a Source of Excitatory and Inhibitory Synaptic Input to the Nucleus Tractus Solitarii

“…The InM has previously been shown to receive afferent inputs from neck muscles (Bakker et al, 1984;Edney and Porter, 1986;Imamura et al, 1986;Stechison and Saintcyr, 1986;Pfaller and Arvidsson, 1988;Prihoda et al, 1991;Paxinos et al, 1999). Neck muscle afferent stimulation is involved in postural reflexes such as the cervicocollic reflex and interacts with information from the vestibular system to maintain posture.…”

“…One target for sensory information from neck muscles is the cervical spinal cord where terminations can be found in the dorsal horn (although sparse) and the central cervical nucleus (CCN) (Bakker et al, 1984;Pfaller and Arvidsson, 1988;Prihoda et al, 1991). The CCN projection is generally considered to underlie spinal somatic reflex circuits, such as those for the tonic neck reflex involved in postural control (Wilson et al, 1984;Brink et al, 1985;Hongo et al, 1988;Popova et al, 1995).…”

“…The CCN projection is generally considered to underlie spinal somatic reflex circuits, such as those for the tonic neck reflex involved in postural control (Wilson et al, 1984;Brink et al, 1985;Hongo et al, 1988;Popova et al, 1995). There is also a strong direct neck muscle afferent projection to the medulla oblongata where fibers terminate in the external cuneate nucleus and a nucleus located at the lateral edges of the dorsal aspect of the hypoglossal motor nucleus (XII), referred to either as the intermediate nucleus of the medulla (InM), as first named by Ramó n y Cajal (1995), or as a rostral continuation of the CCN (Bakker et al, 1984;Edney and Porter, 1986;Imamura et al, 1986;Stechison and Saintcyr, 1986;Pfaller and Arvidsson, 1988;Prihoda et al, 1991;Paxinos et al, 1999). However, regardless of terminology, this nucleus remains extremely poorly characterized in the brainstem.…”

Morphometric analysis of the human vestibular nuclei

“…Both LVN and MVN have a majority of neurons that project to the abducens nucleus clustered in separate regions of the rostral part of these nuclei (Highstein and McCrea, 1988). However, the caudodorsal part of MVN does not receive vestibular afferent fibers (Brodal and Pompeiano, 1957;Stein and Carpenter, 1967;Gacek, 1969;Suá rez et al, 1989a;Newman et al, 1992), whereas some spinal afferents end in this region (Brodal and Pompeiano, 1957;Henkel and Martin, 1977a;Rubertone and Haines, 1982;Prihoda et al, 1991).…”