Inhibition of the responses of neurons in the rat spinal cord to noxious skin heating by stimulation in midbrain periaqueductal gray or lateral reticular formation

Earl Carstens, L. R. Watkins

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Single units responsive to noxious heating of glabrous hindfoot skin were recorded in the lumbar spinal cord of rats anesthetized with sodium pentobarbital. Unit responses to heat stimuli (e.g. 50 °C, 10 s) delivered at 2-min intervals were stable and were markedly suppressed during stimulation (100-ms pulse trains at 100 Hz, 3/s, 25-400 μA) in the midbrain periaqueductal gray (PAG) or lateral reticular formation (LRF). Inhibition did not appear to outlast the midbrain stimulation period. By systematically varying the position of an array of 3 or 5 stimulating electrodes, we observed that stimulation in PAG and subjacent tegmental areas, as well as in widespread regions of the LRF bilaterally, suppressed unit responses to noxious skin heating. The degree of suppression of unit responses increased with graded increases in PAG or LRF stimulation intensity. LRF appeared to be more efficacious than PAG stimulation, based on lower currents at threshold, as well as on significantly greater slopes in current-inhibition plots for LRF compared to PAG stimulation. Unit responses increased linearly with graded increases in stimulus temperature from 42 to 54 °C. Slopes of temperature-response lines were reduced during PAG stimulation with no change in response threshold, while temperature-response lines were shifted in a parallel manner toward higher temperatures during LRF stimulation with an increase in response threshold. The results suggest that differential inhibitory systems are activated by PAG or LRF stimulation and are discussed in relation to previous findings in the cat and as a possible mechanism of stimulation-produced analgesia.

Original languageEnglish (US)
Pages (from-to)266-277
Number of pages12
JournalBrain Research
Volume382
Issue number2
DOIs
StatePublished - Sep 24 1986

Fingerprint

Periaqueductal Gray
Reticular Formation
Mesencephalon
Heating
Spinal Cord
Neurons
Skin
Temperature
Pentobarbital
Analgesia
Electrodes
Cats
Hot Temperature

Keywords

  • descending inhibition
  • dorsal horn neuron
  • midbrain periaqueductal gray
  • noxious heat-evoked response
  • rat
  • reticular formation

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

Cite this

Inhibition of the responses of neurons in the rat spinal cord to noxious skin heating by stimulation in midbrain periaqueductal gray or lateral reticular formation. / Carstens, Earl; Watkins, L. R.

In: Brain Research, Vol. 382, No. 2, 24.09.1986, p. 266-277.

Research output: Contribution to journalArticle

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