摘要
The effect of intrathecal injection of dynorphin A (1-17) on second messenger systems of spinal cord relative to behavioral change in rats was studied. Dynorphin A (1-17) 5 ,10 (20nmol) caused dose-dependent flaccid paralysis of hindlimbs. Dynorphin A (1-17) 10, 20 nmol dose-dependently decreased spinal adenylate cyclase (AC) activity, cyclic AMP production, calmodulin (CaM) level and cyclic-nucleotide phosphodiesterase(PDE)activity 10 min after intrathecal injection. They recovered to a varying extent two hours later. Pretreatment with selective κ-opioid receptor antagonist nor-BNI 30 nmol 10 min before dynorphin A (1-17) markedly antagonized the effects of dynorphin A (1-17 ) at 20 nmol on hindlimb paralysis and inhibition of intracellular second messengers. The L-type calcium channel blocker verapamil (100nmol) also played a role in blocking dynorphin neurotoxicity. The NMDA receptor antagonist APV could partially or completely block dynorphin inhibition of CaM level and PDE activity without affecting paralysis and decrease of AC-cAMP level induced by dynorphin A(1-17) 10 min after intrathecal injection.
