Opioid alkaloids and peptides

The roles of calcium and calcium antagonists in the central nervous system are dealt with in the next two chapters. From Dr. Leong Way s laboratory comes an overview of the mechanism of interaction between calcium and opioid alkaloids and peptides, while Dr. Ferrendelli reviews... 

Pharmacologic Consequences of Calcium Interactions with Opioid Alkaloids and Peptides... 

Kampa, M., Bakogeorgou, E., Hatzoglou, A., Damianaki, A., Martin, P.-M., and Castanas, E. 1997. Opioid alkaloids and casomorphin peptides decrease the proliferation of prostatic cancer cell lines (LNCaP, PC3 and DU145) through a partial interaction with opioid receptors. Fur. J. Pharmacol 335, 255-265. 

The opioid peptides isolated from mammalian tissue are known collectively as endorphins, a word that is derived from a combination of endogenous and morphine. The opioid alkaloids and all of the synthetic opioid derivatives are exogenous opioids. Interestingly, the isolation of morphine and codeine in small amounts has been reported from mammalian brain (9). The functional significance of endogenous morphine remains unknown. 

Shen and Crain [13] tested the effects of biphalin on naive and chronic morphine-treated dorsal root ganglion (DRG) neurons in cell culture. At low (pM-nM) concentrations, most mu, delta, or kappa opioid peptides as well as morphine and other opioid alkaloids elicit dose-dependent excitatory prolongation of the calcium-dependent component of the action potential duration (APD) of many mouse sensory DRG neurons. In contrast, application of the same opioids at higher (pM) concentrations results in inhibitory shortening of the APD [14]. Biphalin at a low concentration elicits only dose-... 

During the mid-1970s the search for endogenous ligands for opioid receptors led to the discovery of peptides with opiate-like activity. The first opioid peptides reported were the pentapeptides leucine and methionine enkephalin (Sand 4) (7), followed shortly thereafter by dynorphin A (3 8) (260,261) and ( endorphin (51)(262). Because these peptides are structurally distinct from the alkaloid opiates, the term opioid was introduced to describe all compounds, both nonpeptide and peptide, with opiate-like activity. These mammalian opioid peptides share a common N-terminal tetrapeptide sequence, but differ in their C-terminal residues (Fig. 7.9). They also differ in... 

Schwyzer R. Estimated membrane structure and receptor subtype selection of an opioid alkaloid-peptide hybrid. Inti J Peptides Protein Res 1988 32,476-483. 

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