Comparison of responses of cutaneous nociceptive and nonnociceptive brain stem neurons in trigeminal subnucleus caudal is (medullary dorsal horn) and subnucleus oralis to natural and electrical stimulation of tooth pulp

The activity of 160 single neurons excited by electrical stimulation of the canine tooth pulp was studied in the subnucleus caudalis (medullary dorsal horn) and the subnucleus oralis of the trigeminal (V) spinal tract nucleus in chloralose-anesthetized cats to test the effects of natural as well as electrical stimulation of the tooth pulp. The neurons were functionally classified on the basis of their cutaneous receptive-field properties as low-threshold mechanoreceptive (LTM), wide dynamic range (WDR), or nociceptive specific (NS). The orofacial receptive-field properties and responses evoked by electrical stimulation of the tooth pulp indicated that the oralis and caudalis neurons examined had characteristics typical of those previously documented for oralis LTM neurons and for caudalis LTM, WDR, and NS neurons. Each neuron was also tested with cold and warm stimulation of the canine tooth, and some neurons were also tested for responsiveness to thermal stimulation of the premolar tooth or to mechanical and chemical stimuli delivered to the dentine of the canine tooth. Although all the neurons could be excited by electrical stimulation of the pulp, we found that the only neurons that consistently responded to thermal pulp stimuli were those located in the V subnucleus caudalis. Moreover, only those caudalis neurons that had been functionally classified as nociceptive (4 WDR and 21 NS neurons) showed this responsiveness. Heating of the canine or premolar tooth excited 24 of these 25 nociceptive neurons; cooling activated only 3, and none of the small number of neurons tested with mechanical and chemical stimulation of the dentine was excited. The response of the nociceptive neurons to heating of the tooth contrasted with the responses of the same neurons to pinching and heating of their cutaneous receptive field.(ABSTRACT TRUNCATED AT 400 WORDS)

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Effects of temporomandibular joint stimulation on nociceptive and nonnociceptive neurons of the cat's trigeminal subnucleus caudalis (medullary dorsal horn)

Journal of Neurophysiology ◽

10.1152/jn.1988.59.5.1575 ◽

1988 ◽

Vol 59 (5) ◽

pp. 1575-1589 ◽

Cited By ~ 71

Author(s):

J. G. Broton ◽

J. W. Hu ◽

B. J. Sessle

Keyword(s):

Electrical Stimulation ◽

Temporomandibular Joint ◽

Dorsal Horn ◽

Dynamic Range ◽

Chemical Stimulation ◽

Tooth Pulp ◽

Nociceptive Neurons ◽

Medullary Dorsal Horn ◽

Afferent Inputs ◽

Stimulation Of

1. The extracellular activity of 196 single neurons in subnucleus caudalis (medullary dorsal horn) of the trigeminal (V) spinal tract nucleus was examined in chloralose-anesthesized, paralyzed cats. Electrical, mechanical, and algesic chemical stimuli were applied to the exposed temporomandibular joint (TMJ) in order to activate TMJ afferents. Seventy-eight neurons were studied that responded to electrical stimulation of the TMJ at a mean latency of 9.9 +/- 4.8 (SD) ms. 2. All neurons with TMJ input received additional afferent input, predominantly from facial skin or intraoral sites. Caudalis neurons were classified on the basis of their cutaneous mechanoreceptive field properties as low-threshold mechanoreceptive (LTM), wide dynamic range (WDR), or nociceptive specific (NS); a few neurons unresponsive to cutaneous stimuli were responsive to manipulation of deep subcutaneous structures. A sample of caudalis neurons was tested for responsiveness to electrical TMJ stimulation after the mechanoreceptive field properties of the neurons were determined. In this sample, 24% of the LTM neurons, 29% of the WDR neurons, 36% of the NS neurons, and 57% of the neurons with input from deep structures were responsive to TMJ stimulation. The WDR and NS neurons with TMJ inputs had mechanoreceptive field properties and laminar locations in caudalis that were comparable to those previously described for cutaneous nociceptive neurons in caudalis; also in accordance with recent studies, 74% of the neurons tested showed convergence of tooth pulp and/or hypoglossal (XII) nerve afferent inputs. 3. In contrast to the LTM neurons, the WDR and NS neurons were especially responsive to intense mechanical and algesic chemical stimulation of the TMJ as well as to electrical stimulation of TMJ afferents. For example, 71% of the WDR and NS neurons excited by electrical stimulation of the TMJ afferents and tested for their responsiveness to injections of algesic chemicals (7% NaCl, KCl, bradykinin, histamine) into the TMJ responded to at least one of these chemicals. The temporal characteristics of these responses were quantified. 4. The TMJ afferent inputs to the WDR and NS neurons were considered to be predominantly of a nociceptive character because of (1) the long latency and high threshold of most TMJ-evoked responses, which are consistent with previous demonstrations that small-diameter afferents predominantly supply the TMJ and, (2) the preferential responsiveness to noxious mechanical and chemical stimulation of TMJ afferents of neurons which were functionally identified as cutaneous nociceptive neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

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Postsynaptic inhibition of cat medullary dorsal horn neurons by stimulation of nucleus raphe magnus and other brain stem sites

Experimental Neurology ◽

10.1016/0014-4886(82)90254-0 ◽

1982 ◽

Vol 77 (2) ◽

pp. 419-435 ◽

Cited By ~ 17

Author(s):

Yasmin Shah ◽

Jonathan O. Dostrovsky

Keyword(s):

Brain Stem ◽

Dorsal Horn ◽

Postsynaptic Inhibition ◽

Nucleus Raphe Magnus ◽

Dorsal Horn Neurons ◽

Medullary Dorsal Horn ◽

Raphe Magnus ◽

Stimulation Of

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Neuronal responses in rostral trigeminal brain-stem nuclei of macaque monkeys after chronic trigeminal tractotomy

Journal of Neurosurgery ◽

10.3171/jns.1986.65.4.0508 ◽

1986 ◽

Vol 65 (4) ◽

pp. 508-516 ◽

Cited By ~ 17

Author(s):

Ronald F. Young ◽

Kent M. Perryman

Keyword(s):

Electrical Stimulation ◽

Brain Stem ◽

Dental Pulp ◽

Afferent Input ◽

Tooth Pulp ◽

Facial Skin ◽

Trigeminal Nucleus ◽

Primary Afferent ◽

Stimulation Of ◽

Relay Neurons

✓ Unilateral trigeminal tractotomy was carried out at the level of the obex, just rostral to the subnucleus caudalis, in five young adult Macaca fascicularis monkeys. The animals had been trained previously to perform a behavioral shock avoidance task in response to electrical stimulation of dental pulp and facial skin. Tractotomy produced an elevation in the stimulus strength which elicited escape behavior when facial skin was stimulated but not when the tooth pulp was stimulated. Unit activity, evoked by electrical stimulation of the tooth pulp and facial skin as well as innocuous and noxious mechanical stimulation of orofacial regions, was recorded from neurons in the trigeminal main sensory nucleus and the subnuclei oralis and interpolaris of the spinal nucleus 8 to 12 weeks after tractotomy. Primary afferent input to these nuclei is unaffected by the tractotomy which is located more caudally. The tractotomy interrupts primary afferent input into the trigeminal nucleus caudalis and also intranuclear connections between caudalis and the more rostral nuclei. Forty-one units contralateral and 47 ipsilateral to the tractotomy were studied. Thirty-six of the units responded only to low-threshold mechanical or electrical stimulation of orofacial zones, 46 were responsive to innocuous mechanical and electrical stimulation of orofacial zones and also to electrical stimulation of the dental pulp. Six units responded only to dental pulp stimulation. No statistically significant differences between the populations of neurons ipsilateral and contralateral to the tractotomies were found relating to the size or location of the peripheral receptive fields, latencies, thresholds, mean firing densities, or responsiveness to the various forms of stimulation. The behavioral results suggest that trigeminal relay neurons rostral to the obex are able to signal dental pain sensation, and the physiological studies confirm that the firing of such neurons is unaffected by tractotomy. The physiological studies demonstrate that the firing patterns of relay neurons activated by natural and electrical cutaneous facial stimuli and which are located in trigeminal brain-stem nuclei rostral to the obex are also not affected by tractotomy. The cutaneous facial analgesia observed after tractotomy thus appears to be due to deafferentation of relay neurons in trigeminal nucleus caudalis rather than to alterations in coding patterns in rostrally located trigeminal neurons due to interruption of the intratrigeminal pathway between the caudal and rostral nuclear groups.

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