Projections of cervical nerves to the rat medulla

doi:10.1016/0304-3940(86)90435-0

Neuroscience Letters

Volume 70, Issue 1, 25 September 1986, Pages 46-51

https://doi.org/10.1016/0304-3940(86)90435-0 Get rights and content

Abstract

The central course of dorsal root ganglia (DRG) fibers from C₁, C₂ and C₃, and particularly, their brainstem terminations were studied in rats using anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA HRP). WGA HRP was injected into the exposed DRG, and after 3 days the animals were sacrificed and sections of spinal cord and brainstem were processed with tetramethylbenzidine and examined for anterograde transport. Labeled fiber terminals were identified in the dorsal horn and the central cervical nucleus in the spinal cord, and in the intermediate nucleus, cuneate nucleus, external cuneate nucleus and the caudal portion of the nucleus of the solitary tract (NTS) in the brainstem. The projection of primary sensory fibers to the visceral NTS is suggestive of a functional relationship between upper cervical and vagal nerve afferents. The potential association of these nerves with clinical problems of headache and other cephalgias is of interest.

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Cutaneous and electrically evoked glutamate signaling in the adult rat somatosensory system
2012, Journal of Neuroscience Methods
Citation Excerpt :
The recording sites of MEAs were coated with DiI (1,1′-dioctadecyl-3,3,3′,3′-tetramethyllindocarbocyanine perchlorate, Molecular Probes®, Eugene, OR) mixed in ethanol (Massey et al., 2006) and air-dried. MEAs were lowered dorsal-to-ventral into 2 urethane- or intramuscular ketamine hydrochloride (50 mg/kg), xylazine (6.5 mg/kg), acepromazine (2.5 mg/kg)-anesthetized rats’ medullas at coordinates based on anatomical and electrophysiological maps (Nord, 1967; Basbaum and Hand, 1973; Beck, 1981; Imamura et al., 1986; Webster and Kemplay, 1987; Pfaller and Arvidsson, 1988; Ygge, 1989; Arvidsson and Pfaller, 1990; Maslany et al., 1990, 1991, 1992; LaMotte et al., 1991; Crockett et al., 1993; Bermejo et al., 2003; Massey et al., 2006; Onifer et al., 2007). DiI fluorescence was observed to assess MEA penetration and placement within the cuneate nucleus (Fig. 2b and c).
Glutamate neurotransmission plays critical roles in normal central nervous system (CNS) function, neurodegenerative diseases, and neurotrauma. We determined whether glutamate signaling could be evoked within the anesthetized normal adult rat CNS with clinically relevant peripheral stimulation and recorded (at >1 Hz) with glutamate-sensitive, ceramic microelectrode arrays (MEAs). Basal glutamate levels and both forelimb cutaneous and electrical stimulation-evoked glutamate release were measured within the cuneate nucleus, a relay of the mammalian dorsal columns somatosensory system. The MEAs with triangular, sharp-point tips were more effective at tissue penetration than the flat, blunt tips. Basal glutamate levels of 2.1 ± 4.4 μM (mean ± SD, n = 10 animals) were detected from 150 μm to 1200 μm below the brainstem dorsal surface. Cutaneous evoked glutamate signals showed an amplitude of 1.1 ± 1.1 μM and a duration of 7.3 ± 6.5 s (26 signals, n = 6). Electrically evoked signals, like cutaneous ones, were both rapid and slowly rising. Electrically evoked signals, especially those evoked by stimulation trains, were more reproducible and had an amplitude of 1.2 ± 1.4 μM, duration of 19.4 ± 17.3 s, and latency from stimulus onset of 21.3 ± 21.5 s (25 signals, n = 4). In contrast to cutaneous stimulation, glutamate signals evoked by electrical stimulation had longer durations and were recorded primarily in the middle and ventral cuneate nuclei. Importantly, both cutaneous and electrical stimulation of the contralateral forelimb and hindlimbs did not evoke glutamate signaling. With the use of MEAs, these results show, for the first time, somatosensory-pathway specific changes in glutamate levels during peripheral cutaneous and electrical stimulation.
The intermedius nucleus of the medulla: A potential site for the integration of cervical information and the generation of autonomic responses
2009, Journal of Chemical Neuroanatomy
The intermedius nucleus of the medulla (InM) is a small perihypoglossal brainstem nucleus, which receives afferent information from the neck musculature and also descending inputs from the vestibular nuclei, the gustatory portion of the nucleus of the solitary tract (NTS) and cortical areas involved in movements of the tongue. The InM sends monosynaptic projections to both the NTS and the hypoglossal nucleus. It is likely that the InM acts to integrate information from the head and neck and relays this information on to the NTS where suitable autonomic responses can be generated, and also to the hypoglossal nucleus to influence movements of the tongue and upper airways.
Central to the integratory role of the InM is its neurochemical diversity. Neurones within the InM utilise the amino acid transmitters glutamate, GABA and glycine. A proportion of these excitatory and inhibitory neurones also use nitric oxide as a neurotransmitter. Peptidergic transmitters have also been found within InM neurones, although as yet the extent of the pattern of co-localisation between peptidergic and amino acid transmitters in neurones has not been established.
The calcium binding proteins calretinin and parvalbumin are found within the InM in partially overlapping populations. Parvalbumin and calretinin appear to have complementary distributions within the InM, with parvalbumin being predominantly found within GABAergic neurones and calretinin being predominantly found within glutamatergic neurones.
Neurones in the InM receive inputs from glutamatergic sensory afferents. This glutamatergic transmission is conducted through both NMDA and AMPA ionotropic glutamate receptors.
In summary the InM contains a mixed pool of neurones including glutamatergic and GABAergic in addition to peptidergic neurones. Neurones within the InM receive inputs from the upper cervical region, descending inputs from brain regions involved in tongue movements and those involved in the co-ordination of the autonomic nervous system. Outputs from the InM to the NTS and hypoglossal nucleus suggest a possible role in the co-ordination of tongue movements and autonomic responses to changes in posture.
Loss and spontaneous recovery of forelimb evoked potentials in both the adult rat cuneate nucleus and somatosensory cortex following contusive cervical spinal cord injury
2007, Experimental Neurology
Varying degrees of neurologic function spontaneously recovers in humans and animals during the days and months after spinal cord injury (SCI). For example, abolished upper limb somatosensory potentials (SSEPs) and cutaneous sensations can recover in persons post-contusive cervical SCI. To maximize recovery and the development/evaluation of repair strategies, a better understanding of the anatomical locations and physiological processes underlying spontaneous recovery after SCI is needed. As an initial step, the present study examined whether recovery of upper limb SSEPs after contusive cervical SCI was due to the integrity of some spared dorsal column primary afferents that terminate within the cuneate nucleus and not one of several alternate routes. C5–6 contusions were performed on male adult rats. Electrophysiological techniques were used in the same rat to determine forelimb evoked neuronal responses in both cortex (SSEPs) and the cuneate nucleus (terminal extracellular recordings). SSEPs were not evoked 2 days post-SCI but were found at 7 days and beyond, with an observed change in latencies between 7 and 14 days (suggestive of spared axon remyelination). Forelimb evoked activity in the cuneate nucleus at 15 but not 3 days post-injury occurred despite dorsal column damage throughout the cervical injury (as seen histologically). Neuroanatomical tracing (using 1% unconjugated cholera toxin B subunit) confirmed that upper limb primary afferent terminals remained within the cuneate nuclei. Taken together, these results indicate that neural transmission between dorsal column primary afferents and cuneate nuclei neurons is likely involved in the recovery of upper limb SSEPs after contusive cervical SCI.
Separate, parallel sensory and hedonic pathways in the mammalian somatosensory system
2002, Brain Research Bulletin
We propose that separate sensory and hedonic representations exist in each of the primary structures of the somatosensory system, including brainstem, thalamic and cortical components. In the dorsal horn of the spinal cord, the hedonic representation, which consists primarily of nociceptive-specific, wide dynamic range, and thermoreceptive neurons, is located in laminae I and II, while the sensory representation, composed primarily by low-threshold and wide dynamic range neurons, is found in laminae III through V. A similar arrangement is found in the caudal spinal trigeminal nucleus. Based on the available anatomical and electrophysiological data, we then determine the corresponding hedonic and sensory representations in the area of the dorsal column nuclei, ventrobasal and posterior thalamic complex, and cortex. In rodent primary somatosensory cortex, a hedonic representation can be found in laminae Vb and VI. In carnivore and primate primary and secondary somatosensory cortical areas no hedonic representation exists, and the activities of neurons in both areas represent the sensory aspect exclusively. However, there is a hedonic representation in the posterior part of insular cortex, bordering on retroinsular cortex, that receives projections from two thalamic areas in which hedonics are represented. The functions of the segregated components of the system are discussed, especially in relation to the subjective awareness of pain.
Calretinin in rat brain: An immunohistochemical study
1992, Neuroscience
Calretinin is a calcium-binding protein related to calbindin-D28k; both are present in different though overlapping sets of neurons in brains of birds and mammals. We describe in detail the pattern of calretinin immunoreactivity in the rat brain. As in chick brain, calretinin immunoreactivity is abundant in various sensory pathways (particularly certain cells and fibres of the cochlear nuclei and olfactory bulb), in the heterogeneous parts of the brainstem and in parts of the hypothalamus. Many primary sensory fibres are strongly positive. Major groups of calretinin-positive neurons also include the thalamic reticular nucleus, triangular septal nucleus, lateral mammillary nucleus and substantia nigra pars compacta. Many other calretinin-positive cells are recognizable as local inhibitory neurons. Calretinin is absent from all but a few cells in the cerebral cortex, and is never found in motor neurons. There are also some distinctive positive structures whose identity is uncertain, notably irregular “shells” of cells and fibres around the thalamus and in the amygdala and an unnamed cell type in the vestibulocerebellum.
Somatotopic organization of the dorsal column nuclei in the rat: transganglionic labelling with B-HRP and WGA-HRP
1991, Brain Research
To analyze the patterns of cutaneous primary afferent fibers projecting to the dorsal column nuclei in the rat, horseradish peroxidase (HRP)-based tracers were injected intracutaneously into a number of discrete regions of the forelimbs and hindlimbs. Three-4 days following the HRP injections, the rats were perfused transcardially; 60 μm transverse sections were cut, and the HRP was reacted using the tetramethyl benzidine method. Comparisons were made of projections following injections with choleragenoid-conjugated horseradish peroxidase (B-HRP) or with wheat-germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). B-HRP and WGA-HRP produced similar patterns of labelling, but B-HRP produced greater intensity of labelling and slightly larger projection areas. In the cuneate nucleus (CN), HRP labelling of primary afferents from small, delimited regions, e.g., from a portion of the skin of a single digit, appeared to be precisely restricted in rostrocaudally oriented columns, with little or no overlap (in the mediolateral and dorsoventral plane) into adjacent regions. With respect to rostrocaudal organization, a region in the CN containing a dense population of cutaneous primary afferent fibers appeared to be similar to the middle, or cluster, region in cats and in raccoons and the pars rotunda in primates. Projection patterns were very consistent from rat to rat, but their somatotopic organization differed from that suggested by electrophysiological studies: cutaneous afferents from forelimb digit 1 projected near the ventral border of the CN; those from digit 5 projected dorsomedially to those from digit 1; the projections from the remaining digits formed a crescent between the projections from digits 1 and 5. In the gracile nucleus, the organization of cutaneous afferent projections from hindlimb digits was more variable and complex than that found in the CN.

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Projections of cervical nerves to the rat medulla

Abstract

J. Auton. Nerv. Syst.

Brain Res.

Brain Res. Bull.

Exp. Neurol.

Neuroscience

Neurosci. Lett.

Central projections from cat suboccipital muscles: a study using transganglionic transport of horseradish peroxidase

J. Comp. Neurol.

Projections of cervicothoracic dorsal roots to the cuneate nucleus of the rat, with observations on cellular ‘bricks’

J. Comp. Neurol.

Peripheral and central connections of the upper cervical dorsal root ganglia in the Rhesus monkey

J. Comp. Neurol.

Intramedullary course of the dorsal root fibers of each of the first four cervical nerves

J. Comp. Neurol.