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Injections of Algesic Solutions into Muscle Activate the Lateral Reticular Formation: A Nociceptive Relay of the Spinoreticulothalamic Tract.

Panneton WM, Gan Q, Ariel M - PLoS ONE (2015)

Bottom Line: Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons.The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases.Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, MO, United States of America.

ABSTRACT
Although musculoskeletal pain disorders are common clinically, the central processing of muscle pain is little understood. The present study reports on central neurons activated by injections of algesic solutions into the gastrocnemius muscle of the rat, and their subsequent localization by c-Fos immunohistochemistry in the spinal cord and brainstem. An injection (300 μl) of an algesic solution (6% hypertonic saline, pH 4.0 acetate buffer, or 0.05% capsaicin) was made into the gastrocnemius muscle and the distribution of immunolabeled neurons compared to that obtained after control injections of phosphate buffered saline [pH 7.0]. Most labeled neurons in the spinal cord were found in laminae IV-V, VI, VII and X, comparing favorably with other studies, with fewer labeled neurons in laminae I and II. This finding is consistent with the diffuse pain perception due to noxious stimuli to muscles mediated by sensory fibers to deep spinal neurons as compared to more restricted pain localization during noxious stimuli to skin mediated by sensory fibers to superficial laminae. Numerous neurons were immunolabeled in the brainstem, predominantly in the lateral reticular formation (LRF). Labeled neurons were found bilaterally in the caudalmost ventrolateral medulla, where neurons responsive to noxious stimulation of cutaneous and visceral structures lie. Immunolabeled neurons in the LRF continued rostrally and dorsally along the intermediate reticular nucleus in the medulla, including the subnucleus reticularis dorsalis caudally and the parvicellular reticular nucleus more rostrally, and through the pons medial and lateral to the motor trigeminal nucleus, including the subcoerulear network. Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons. The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases. The internal lateral subnucleus of the parabrachial complex was labeled moderately. Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently. These data are discussed in terms of an interoceptive, multisynaptic spinoreticulothalamic path, with its large receptive fields and role in the motivational-affective components of pain perceptions.

No MeSH data available.


Related in: MedlinePlus

Photomontages at the level of the trigeminal motor nucleus (between 0.18–0.42 mm caudal to interaural zero) after a unilateral injection of capsaicin (A), low pH (B), or 6% saline (C) into the right GCM.The areas outlined on the right of the sections demarcate the LRF as defined by the authors; note the presence of immunoreactive profiles in the LRF bilaterally. Other areas showing c-Fos also were labeled in control cases.
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pone.0130939.g006: Photomontages at the level of the trigeminal motor nucleus (between 0.18–0.42 mm caudal to interaural zero) after a unilateral injection of capsaicin (A), low pH (B), or 6% saline (C) into the right GCM.The areas outlined on the right of the sections demarcate the LRF as defined by the authors; note the presence of immunoreactive profiles in the LRF bilaterally. Other areas showing c-Fos also were labeled in control cases.

Mentions: Immunolabeled neurons with antibodies against c-Fos were increased greatly after injections of algesic solutions into the GCM in the brainstem, especially in an area we designate as the lateral reticular formation. This area designated as the LRF is outlined in Figs 3, 4, 5 and 6. In the caudal medulla (Fig 1E, Fig 3), a high percentage of neurons immunolabeled with c-Fos just dorsal to the lateral reticular nucleus also were catecholaminergic (Fig 3I) and these labeled neurons were in the A1 group. Increased immunolabeling with c-Fos was present in the caudalmost ventrolateral medulla (cmVLM; Fig 3B, 3C and 3F), just lateral to the A1 catecholamine cell group (Fig 3I). In contrast, neurons in the magnocellular lateral reticular nucleus (LRt) were labeled rarely. A high density of labeled cells were observed throughout the LRF (Fig 3B, 3F and 3H) along a band called the intermediate reticular nucleus [35]; they then continued into the subnucleus reticularis dorsalis (SRD) and lateral aspects of the solitary complex (Fig 3E and 3H). Neurons in the gracile nucleus (Gr) were labeled bilaterally, as were neurons in the external cuneate nucleus which continues more rostrally.


Injections of Algesic Solutions into Muscle Activate the Lateral Reticular Formation: A Nociceptive Relay of the Spinoreticulothalamic Tract.

Panneton WM, Gan Q, Ariel M - PLoS ONE (2015)

Photomontages at the level of the trigeminal motor nucleus (between 0.18–0.42 mm caudal to interaural zero) after a unilateral injection of capsaicin (A), low pH (B), or 6% saline (C) into the right GCM.The areas outlined on the right of the sections demarcate the LRF as defined by the authors; note the presence of immunoreactive profiles in the LRF bilaterally. Other areas showing c-Fos also were labeled in control cases.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496070&req=5

pone.0130939.g006: Photomontages at the level of the trigeminal motor nucleus (between 0.18–0.42 mm caudal to interaural zero) after a unilateral injection of capsaicin (A), low pH (B), or 6% saline (C) into the right GCM.The areas outlined on the right of the sections demarcate the LRF as defined by the authors; note the presence of immunoreactive profiles in the LRF bilaterally. Other areas showing c-Fos also were labeled in control cases.
Mentions: Immunolabeled neurons with antibodies against c-Fos were increased greatly after injections of algesic solutions into the GCM in the brainstem, especially in an area we designate as the lateral reticular formation. This area designated as the LRF is outlined in Figs 3, 4, 5 and 6. In the caudal medulla (Fig 1E, Fig 3), a high percentage of neurons immunolabeled with c-Fos just dorsal to the lateral reticular nucleus also were catecholaminergic (Fig 3I) and these labeled neurons were in the A1 group. Increased immunolabeling with c-Fos was present in the caudalmost ventrolateral medulla (cmVLM; Fig 3B, 3C and 3F), just lateral to the A1 catecholamine cell group (Fig 3I). In contrast, neurons in the magnocellular lateral reticular nucleus (LRt) were labeled rarely. A high density of labeled cells were observed throughout the LRF (Fig 3B, 3F and 3H) along a band called the intermediate reticular nucleus [35]; they then continued into the subnucleus reticularis dorsalis (SRD) and lateral aspects of the solitary complex (Fig 3E and 3H). Neurons in the gracile nucleus (Gr) were labeled bilaterally, as were neurons in the external cuneate nucleus which continues more rostrally.

Bottom Line: Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons.The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases.Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacological and Physiological Science, Saint Louis University, St. Louis, MO, United States of America.

ABSTRACT
Although musculoskeletal pain disorders are common clinically, the central processing of muscle pain is little understood. The present study reports on central neurons activated by injections of algesic solutions into the gastrocnemius muscle of the rat, and their subsequent localization by c-Fos immunohistochemistry in the spinal cord and brainstem. An injection (300 μl) of an algesic solution (6% hypertonic saline, pH 4.0 acetate buffer, or 0.05% capsaicin) was made into the gastrocnemius muscle and the distribution of immunolabeled neurons compared to that obtained after control injections of phosphate buffered saline [pH 7.0]. Most labeled neurons in the spinal cord were found in laminae IV-V, VI, VII and X, comparing favorably with other studies, with fewer labeled neurons in laminae I and II. This finding is consistent with the diffuse pain perception due to noxious stimuli to muscles mediated by sensory fibers to deep spinal neurons as compared to more restricted pain localization during noxious stimuli to skin mediated by sensory fibers to superficial laminae. Numerous neurons were immunolabeled in the brainstem, predominantly in the lateral reticular formation (LRF). Labeled neurons were found bilaterally in the caudalmost ventrolateral medulla, where neurons responsive to noxious stimulation of cutaneous and visceral structures lie. Immunolabeled neurons in the LRF continued rostrally and dorsally along the intermediate reticular nucleus in the medulla, including the subnucleus reticularis dorsalis caudally and the parvicellular reticular nucleus more rostrally, and through the pons medial and lateral to the motor trigeminal nucleus, including the subcoerulear network. Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons. The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases. The internal lateral subnucleus of the parabrachial complex was labeled moderately. Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently. These data are discussed in terms of an interoceptive, multisynaptic spinoreticulothalamic path, with its large receptive fields and role in the motivational-affective components of pain perceptions.

No MeSH data available.


Related in: MedlinePlus