[Morphine decreased the content of cyclic AMP in the rat spinal cord].

It has been reported that morphine or opiate-like substances (OLS) can affect the contents of cyclic AMP and/or cyclic GMP in mammalian brain, but very little is known whether similar effects also occur in spinal cord. Using RIA method, we showed that morphine significantly decreased the content of cyclic AMP in the rat spinal cord in vivo and in vitro and this effect could be completely blocked by naloxone, while the concentration of cyclic GMP in rat spinal cord is unchanged. In view of the present experiment it is suggested that the changes of cyclic AMP in the central nervous system may be partly mediated by the action of morphine.