Peptide descr

Some of the important therapeutic actions of opioid analgesics (eg, morphine) are mediated via activation of receptors for these endogenous peptides. Another peptide, substance P, is a mediator of slow EPSPs in neurons involved in nociceptive sensory pathways in the spinal cord and brain stem. Peptide transmitters differ from nonpeptide transmitters in that (1) the peptides are synthesized in the cell body and transported to the nerve ending via axonal transport, and (2) no reuptake or specific enzyme mechanisms have been identified for terminating their actions.