Inputs from identified jaw‐muscle spindle afferents to trigeminothalamic neurons in the rat: A double‐labeling study using retrograde HRP and intracellular biotinamide

Abstract

Projections from physiologically identified jaw-muscle spindle afferents onto trigeminothalamic neurons were studied in the rat. Trigeminothalamic neurons were identified by means of retrograde transport of horseradish peroxidase from the ventroposteromedial nucleus of the thalamus. Labeled neurons were found contralaterally in the supratrigeminal region (Vsup), the trigeminal principal sensory nucleus, the ventrolateral part of the trigeminal subnucleus oralis, the spinal trigeminal subnuclei interpolaris and caudalis, the reticular formation, and an area ventral to the trigeminal motor nucleus (Vmo) and medial to the trigeminal principal sensory nucleus (AVM). Jaw-muscle spindle afferents were physiologically identified by their increased firing during stretching of the jaw muscles and intracellularly injected with biotinamide. Axon collaterals and boutons from jaw-muscle spindle afferents were found in Vmo; Vsup; the dorsomedial part of the trigeminal principal sensory nucleus (Vpdm); the dorsomedial part of the spinal trigeminal subnuclei oralis, interpolaris (Vidm) and caudalis; the parvicellular reticular formation (PCRt); and the mesencephalic trigeminal nucleus. Trigeminothalamic neurons in Vsup, Vpdm, Vidm, PCRt, and AVM were associated with axon collaterals and boutons from intracellularly stained jaw-muscle spindle afferents. Trigeminothalamic neurons in Vsup, Vpdm, Vidm, and PCRt were closely apposed by one to 14 intracellularly labeled boutons from jaw-muscle spindle afferents, suggesting a powerful input to some trigeminothalamic neurons. These data demonstrate that muscle length and velocity feedback from jaw-muscle spindle afferents is projected to the contralateral thalamus via multiple regions of the trigeminal system and implicates these pathways in the projection of trigeminal proprioceptive information to the cerebral cortex.

Acute and Chronic Craniofacial Pain: Brainstem Mechanisms of Nociceptive Transmission and Neuroplasticity, and Their Clinical Correlates

“…These include projections to the ventrobasal thalamus and thalamic nucleus submedius. Although some earlier studies had reported that the projection to thalamus from oralis is minor, there is more recent evidence that this may not be the case (e.g., see Magnusson et al, 1987;Kemplay and Webster, 1989;Luo and Dessem, 1995;Dallel et at., 1997).…”

“…Nonetheless, all three components of the spinal tract nucleus also contain thalamicprojecting LTM neurons and so, along with the main sensory nucleus, likely contribute to our appreciation of fine touch. It is clear, from early anatomical investigations based on the distribution of degenerative neural endings in the thalamus following brainstem lesions, as well as from more recent anatomical studies using anterograde and/or retrograde tracers, that there are substantial projections to the thalamus from the subnucleus caudalis and caudal interpolaris (Fukushima and Kerr, 1979;Bruce et at., 1987;Magnusson et at., 1987;Kemplay and Webster, 1989;DiFiglia and Aronin, 1990;Yoshida et al, 1991;Luo and Dessem, 1995;and see Sessle, 1987;Craig and Dostrovsky, 1997). These include projections to the ventrobasal thalamus and thalamic nucleus submedius.…”

Central projection of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive trigeminal primary neurons in the rat

“…Therefore, it may be that the principal relay nucleus involved in the intraoral nociception is the PrV in the cat. Unlike in the cat, the rat's Vo contains a substantial number of neurons that project to the contralateral VPM, although their cell bodies are located mainly in the ventrolateral part of the subnucleus (Luo and Dessem, 1995).…”

Physiological, Morphological and Neurochemical Characterization of Neurons Modulated by Movement

“…The method visualized here can easily be combined with retrograde neuronal labeling. [7][8][9][10] To do this, anesthetize the animal and using aseptic technique, inject a neuronal tracer such as horseradish peroxidase (20% horseradish peroxidase. Sigma VI, Sigma) and 1% wheat-germ aggultinated horseradish peroxidase (Sigma) into peripheral target regions such as the masseter muscle.…”

“…When combined with other techniques such as retrograde neuronal labeling additional information such as neuronal circuitry can be characterized. 7,8 Another advantage of this method is that it can be learned in steps. For instance, intracellular recording can be conducted initially, followed by intracellular staining with immunocytochemistry or retrograde neuronal labeling added after mastery of the initial method.…”