These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


PUBMED FOR HANDHELDS

Search MEDLINE/PubMed


  • Title: Spinal pathways mediating tonic, coeruleospinal, and raphe-spinal descending inhibition in the rat.
    Author: Jones SL, Gebhart GF.
    Journal: J Neurophysiol; 1987 Jul; 58(1):138-59. PubMed ID: 3612222.
    Abstract:
    1. The contribution of midline medullary bulbospinal neurons to descending inhibition from the locus coeruleus (LC) and the funicular trajectories of coeruleo- and raphe-spinal fibers mediating inhibition of spinal nociceptive transmission were examined in different experiments. Extracellular recordings of lumbar dorsal horn neurons were made in deeply pentobarbital-anesthetized, paralyzed rats. All units studied responded to electrical stimulation of the ipsilateral tibial nerve at intensities supramaximal to activate A-alpha-delta- and C-fibers and to mechanical and heat (50 degrees C) stimuli of the glabrous skin of the ipsilateral hind foot. Parallel studies were done in lightly pentobarbital-anesthetized rats utilizing the nociceptive tail-flick (TF) reflex. 2. To examine the contribution of bulbospinal neurons in the nucleus raphe magnus (NRM) to descending coeruleospinal inhibition, lidocaine microinjections were made into the NRM to produce a time-limited, reversible block. Lidocaine microinjections into the NRM effectively blocked NRM stimulation-produced inhibition of the TF reflex (prelidocaine stimulation thresholds were increased two to three times), but did not affect stimulation-produced inhibition from the LC. 3. In parallel electrophysiological studies, stimulation in the NRM inhibited heat-evoked dorsal horn unit activity to 31% of control, whereas stimulation in the LC/SC inhibited heat-evoked activity of the same units to 30% of control. Following NRM lidocaine microinjections, stimulation at the same intensity in the NRM no longer inhibited heat-evoked activity (93% of control), confirming the efficacy of the lidocaine block. LC stimulation-produced inhibition, however, was not affected by blockage of the NRM; heat-evoked unit activity was inhibited by LC stimulation to 39% of control. 4. The effects of ipsilateral and bilateral ventrolateral funiculus (VLF) lidocaine microinjections on spontaneous and heat-evoked unit activity were examined in other experiments. Spontaneous activity increased following ipsilateral VLF lidocaine microinjections for 13/18 units; decreases and no change in spontaneous activity were observed for three and two units, respectively. Heat-evoked unit activity was increased significantly following ipsilateral VLF lidocaine microinjections.(ABSTRACT TRUNCATED AT 400 WORDS)
    [Abstract] [Full Text] [Related] [New Search]