Intrathecal dynorphins suppress hindlimb electromyographic activity in rats

Intrathecal administration of dynorphin A-(1-17) produced suppression of hindlimb electromyographic activity in rats. This effect was seen also with the [D-Ala2]dynorphin (A-(1-17) analog. Intrathecal saline or the prototypical kappa opiate agonist, U50488, did not produce any change in electromyographic activity. These results, along with others, suggest that dynorphin or degradation fragment(s) of dynorphin, induces inhibition of ventral horn output and may possibly have toxic effects on ventral horn cells of the spinal cord.