| pubmed-article:6538507 | pubmed:abstractText | Intravenous morphine depressed the firing of cat dorsal horn neurones to impulses in unmyelinated primary afferents. Electrophoretic administration of naloxone in the substantia gelatinosa between 10 min and 6 h after morphine revealed hyper-responsiveness which was not associated with apparent tolerance to morphine. The observations suggest the changes underlying dependence occur very rapidly in the dorsal horn probably at a site different from that at which morphine acts. | lld:pubmed |
