Dynorphin A(1-13) Acetate In Vitro
Dynorphin A is an endogenous opioid peptide that preferentially activates κ opioid receptors and is antinociceptive at physiological concentrations. Levels of dynorphin A and a major metabolite, Dynorphin A(1-13) Acetate increase significantly following spinal cord trauma and reportedly contribute to neurodegeneration associated with secondary injury. Interestingly, both κ opioid and N-methyl-D-aspartate (NMDA) receptor antagonists can modulate dynorphin toxicity, suggesting that dynorphin is acting (directly or indirectly) through κ opioid and/or NMDA receptor (NMDAR) types.
Despite these findings, few studies have systematically explored dynorphin toxicity at the cellular level in defined populations of neurons co-expressing κ opioid and NMDA receptors. To address this question, we isolated populations of neurons enriched in both κ opioid and NMDA receptors from embryonic mouse spinal cord and examined the effects of Dynorphin A(1-13) Acetate on intracellular calcium concentration ([Ca2+]i) and neuronal survival in vitro.
Time-lapse photography was used to repeatedly follow the same neurons before and during experimental treatments. At micromolar concentrations, Dynorphin A(1-13) Acetate elevated [Ca2+]i and caused a significant loss of neurons.