We found that spinorphin, a novel neuropeptide showed analgesia in a different manner compared with morphine. By measuring flexor responses induced by the intraplanter injection of substances, the presence of three different types of sensory neurons were demonstrated. Although spinorphin completely blocked 2-metylthioadenosine (2-MeS ATP, a P2X3 agonist)-induced responses, morphine did not. On the other hand, morphine-induced blockade of bradykinin (BK, a B2-receptor agonist)-responses was attenuated by pertussis toxin (PTX) treatment, whereas that of spinorphin was not. Thus it is suggested that spinorphin has a spectrum of analgesia which covers the blockade of nociception insensitive to morphine. (C) 2000 Elsevier Science Inc.
- 2-MeS ATP
- PGI agonist
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience