Effects of morphine on the Rexed lamina VII spinal neuronal response to graded noxious radiant heat stimulation
1978; Elsevier BV; Volume: 62; Issue: 1 Linguagem: Inglês
10.1016/0014-4886(78)90047-x
ISSN1090-2430
AutoresHidenori Toyooka, Luke M. Kitahata, Shuji Dohi, Minako Ohtani, Kazuo Hanaoka, Arthur Taub,
Tópico(s)Veterinary Pharmacology and Anesthesia
ResumoMorphine sulfate exerts its analgesic action in part through suppression of the activity of spinal cord nociceptive neurons. Cells in Rexed lamina VII are considered to be the cells of origin of the spinothalamic and spinoreticular tracts concerned with nociception. Using graded radiant heat to their peripheral receptive fields, the relationship between the intensity of heat (millicalories per square centimeter per second) which produces noxious stimuli and the response frequency of single units in Rexed lamina VII of the spinal cord was analyzed with extracellular microelectrode recording techniques in 15 decerebrated and spinal-transected cats before and after administration of morphine sulfate (1 mg/kg, iv). A linear relationship between the intensity of heat and the frequency of response discharge was observed (above threshold) both in the control study and after the administration of morphine. Morphine sulfate significantly suppressed the spontaneous activity of the units studied, raised the threshold of their evoked activity to varying intensities of heat, and diminished the slope of the heat intensity vs evoked single-unit response relationship. Naloxone (0.02 mg/kg, iv) eliminated all changes brought about by morphine sulfate.
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