Effects of ethylketocyclazocine on adrenergic transmission in the isolated perfused cat spleen.

The pre- and postsynaptic effects of ethylketocyclazocine (EKC), a putative kappa opiate receptor agonist, on sympathetic adrenergic neurotransmission were investigated using the isolated perfused cat spleen. Perfusion of spleens with EKC (10(-7) and 10(-6)M) produced a modest dose-dependent inhibition of nerve-stimulation-mediated overflow of norepinephrine (NE) and total 3H. In contrast, EKC (10(-4)M) produced an increase in the release of NE, and total 3H overflow. Perfusion with EKC (10(-5) and 10(-4)M) resulted in a dose-dependent inhibition of the postsynaptic response to stimulation-mediated release of NE. Likewise, EKC inhibited splenic contraction due to exogenously administered NE which was not antagonized by naloxone. These results suggest that EKC exerts a direct effect on peripheral adrenergic neurotransmission not mediated via classical kappa opiate receptors.