Korean J Physiol Pharmacol.  1998 Apr;2(2):155-163.

Comparison of somatostatin and morphine action on the responses of wide dynamic range cells in the dorsal horn to peripheral noxious mechanical and heat stimulation in cats

• Jung SJ
• Choi YI
• Kim J

Abstract

The purpose of present study was to compare the effects of somatostatin (SOM) and morphine (Mor) on the responses of wide dynamic range (WDR) cells to peripheral noxious stimulation. Single neuronal activity was recorded with a carbon-filament electrode at the lumbosacral enlargement of cat spinal cord. After identifying WDR cells, their responses to peripheral noxious mechanical or thermal stimuli were characterized and the effects of SOM and Mor, applied either iontophoretically or intrathecally, were studied. In most cells SOM and Mor suppressed noxious stimulus-evoked WDR neuronal activity, though a few WDR neurons showed no change or were excited by SOM and Mor. Systemically applied naloxone, a non-specific opioid antagonist, always reversed the Mor induced suppression of neuronal activity evoked by noxious mechanical stimuli, but did not always reverse the suppression of neuronal activity elicited by SOM. The suppressive effect of Mor on thermal stimulus-evoked neuronal activity was partially reversed by naloxone, while that of SOM were not reversed at all. The above results suggest that both Mor and SOM exert an inhibitory effect on thermal and mechanical stimulus-evoked WDR neuronal activity in cat spinal dorsal horn, but the mechanisms are dependent upon the functional populations of dorsal horn nociceptive neurons.

Keyword

WDR cells; Somatostatin; Morphine; Mechanical and thermal noxious stimuli

MeSH Terms

Animals
Cats*
Electrodes
Horns*
Hot Temperature*
Morphine*
Naloxone
Neurons
Nociceptors
Somatostatin*
Spinal Cord
Morphine
Naloxone
Somatostatin