Projections of nucleus caudalis and spinal cord to rrainstem and diencephalon in the hedgehog (Erinaceus europaeus and Paraechinus aethiopicus): A degeneration study

Abstract

In the light of hypotheses related to the evolution of pain-carrying systems in mammals, terminal projection fields in brainstem and diencephalon of efferents of nucleus caudalis (NC) of the spinal trigeminal complex and spinal cord were determined in hedgehog by using Nauta-Gygax and Fink-Heimer silver techniques for degeneration. Unilateral NC lesions resulted in medullary degeneration in the ventral portion of NC contralaterally and bilaterally in cuneate nucleus (CU) and reticular formation. Pontine degeneration was noted ipsilaterally in medial (PBM) and lateral (PBL) parabrachial, facial motor (VII), and interpolar, oral, and main sensory trigeminal nuclei; degeneration in reticular formation was bilateral. Midbrain degeneration was seen bilaterally in caudal superior colliculus (SC), inferior colliculus (IC), periaqueductal gray, and tegmentum. In thalamus, projections to ventroposterior nucleus (VP) were contralateral and concentrated in a crescent extending along the lateral one-third-to-one-half and ventral border of the nucleus. Bilateral degeneration fields were noted in a dorsomedial sector of the "ventral nuclear field," posterior complex (PO), and mediodorsal nucleus (MD), the degeneration always heavier contralaterally in these nuclei. Sparse degeneration was noted in the medial most portions of the medial geniculate nuclei bordering PO and VP. In rostral diencephalon, bilateral degeneration was traced from the inferior thalamic peduncle to the lateral hypothalamic area (LH). Unilateral spinal cord lesions made between C7 and T1 vertebrae resulted in medullary degeneration in NC contralaterally, ipsilaterally in CU and lateral cuneate nucleus, and bilaterally in gracile nucleus, inferior olivary complex, and reticular formation. Pontine degeneration was limited to ipsilateral PBL and bilaterally to VII. Midbrain degeneration was found bilaterally in IC, SC, nucleus sagulum, and tegmentum; a minor projection was noted in interpeduncular nucleus. In thalamus, projections were confined to ipsilateral PO and zona incerta. In rostral diencephalon bilateral fields were noted in LH. NC terminations in PO and VP parallel results of research in hedgehogs on thalamic projections of the dorsal column nuclei (Jane and Schroeder, '71), and particularly the location in VP of most cells responsive to stimulation of the face (Erickson et al., '67). This suggests that somatic input from NC, some of which may be pain-specific, reaches thalamic areas, a portion of whose neurons are characterized as polymodal and at least partially convergent for somatotopy. These results are consistent with the thesis that specific sensory thalamic nuclei evolved from a diffuse sensory region. Response properties of neurons in the dorsomedial portion of the ventral nuclear field, an area which are also received NC efferents, are not known. Last, NC projections to MD and LH implicate the role of "limbic" aspects of nociception.

Morphology and connections of intratrigeminal cells and axons in the macaque monkey

“…This anatomical difference reinforces the physiological and pharmacological differences observed between sVi and sVc (Bereiter, 1997; Hirata et al, 2000, 2004). In general, the distribution of labeled neurons demonstrated in this study is reminiscent of a distribution pattern shared by other mammalian species, including rats (Falls, 1984a; Jacquin et al, 1990b; Voisin et al, 2002), cats (Carpenter and Hanna, 1961; Stewart and King, 1963; Hockfield and Gobel, 1982; Ikeda et al, 1982, 1984; Panneton and Burton, 1982; Lovick and Wolstencroft, 1983; Somers and Panneton, 1985; Nasution and Shigenaga, 1987), hedgehogs (Ring and Ganchrow, 1983), sheep (Roberts and Matzke, 1971), and other non-human primates (Dunn and Matzke, 1968; Kruger, 1971; Tiwari and King, 1974; Smith, 1975; Kruger et al, 1977; Ganchrow, 1978) suggesting a common mammalian pattern.…”

Insectivora

“…Gould and Ebner (1968b) investigated interlaminar connections and found that both vertical and horizontal connections are important and that horizontal projections originate at three distinct cortical depths. Earle and Matzke (1974), Schroeder and Jane (1976), Ganchrow and Ring (1979), and Ring and Ganchrow (1983); in Hemiechinus auritus by Earle and Matzke (1974) and Moore et a1. (1977); and in Paraechinus aethiopicus by Ring and Ganchrow (1983).…”

“…Earle and Matzke (1974), Schroeder and Jane (1976), Ganchrow and Ring (1979), and Ring and Ganchrow (1983); in Hemiechinus auritus by Earle and Matzke (1974) and Moore et a1. (1977); and in Paraechinus aethiopicus by Ring and Ganchrow (1983). Schroeder et al (1970) mentioned projections from the dorsal column of the spinal cord, cerebellar nuclei, and tectum to the thalamus.…”

“…Projections from these nuclei to the inferior colliculi were described by Schroeder and Jane (1976). The projections from the nucleus caudalis (NC) and spinal cord to brain stem and diencephalon were also studied by Ganchrow and Ring (1979) and Ring and Ganchrow (1983). Their results suggest "that somatic input from NC, some of which may be pain-specific, reaches those thalamic areas, a portion of whose neurons are characterized as polymodal and at least partially convergent for somatotopy."…”

Artificial Dental Pulp Exposure Injury Up-regulates Antigen-Presenting Cell–related Molecules in Rat Central Nervous System

“…The thalamus was studied because it plays an important role in the limbic aspects of nociception (16) and receives sensory signals from the pulp via the secondary afferents from the trigeminal brainstem complex (7,8). We conducted immunohistochemical and gene expression analysis for selected antigen-presenting cell-related molecules in the thalamus at 24 hours after pulp exposure, when the coronal pulp is inflamed and undergoing necrosis but the root pulp tissue is still vital (17).…”