OPIOID INHIBITED CAMP IN MOUSE SPINAL-CORD AND STRIATUM

In the present studies the regulation of cAMP by the opioid peptide DA DLE was examined in mouse striatum and spinal cord. For comparison, DA DLE inhibition of cAMP was examined in the rat striatum. In all three tissue preparations (mouse and rat striatum and mouse spinal cord) DAD LE inhibited cAMP in a dose-dependent manner. Mouse and rat striatum w ere equally sensitive to DADLE inhibition of cAMP, while mouse cord wa s less sensitive. Naloxone reversed the effect of DADLE in the rat str iatum. Conversely, the DADLE effect was not naloxone reversible in the mouse striatum and spinal cord. In addition, naloxone by itself reduc ed basal cAMP dose-dependently in the mouse striatum. Chronic in vivo naltrexone treatment increased the in vitro potency of DADLE to inhibi t cAMP in the rat striatum. However, naltrexone treatment did not incr ease sensitivity to DADLE in the mouse striatum and mouse spinal cord. Overall, opioid effects on cAMP in mouse striatum and spinal cord dif fer from that measured in rat striatum.