Exogenous opiates

Jones RT Dependence in non-addict humans after a single dose of morphine, in Endogenous and exogenous opiate agonists and antagonists. Edited by Way EL. New York, Pergamon, 1979, pp 557-560... 

Within each exogenous opiate family there are analogues which are pure agonists, pure antagonists and those which are mixed agonist-antagonists. One clinically promising... 

Will opiate antagonists affect a person to whom exogenous opiates have not been administered ... 

The chemical transmitters may be small molecules— notably acetylcholine, norepinephrine, epinephrine, serotonin, dopamine, or histamine. Acetylcholine and norpeinephrine are the dominant neurotransmitters in the parasympathetic and sympathetic nervous systems, respectively. Dopamine and serotonin are employed primarily in the central nervous system. Neurotransmitters may also be more complex peptides (small proteins) such as substance P, vasopressin, endorphins, and enkephalins. The latter agents are of particular importance to our considerations of opium since they represent the endogenous opiates—agents that exist within the body whose actions are mimicked by exogenous, or outside, agents such as morphine, heroin, codeine, and so on. These neurotransmitters serve to convey information between neurons across the synaptic cleft (the junction where two neurons meet) or at the neuroeffector junction (the site between neuron and an innervated organ such as muscle or secretory gland). 

Correspondingly, many papers have now appeared which concern metal ion (and especially Ca +) interactions with opiates, and each year a considerable number of new reports are published. This literature has been the subject of several reviews (JL- ). In the present article this body of work is considered in terms of the general hypothesis that neuronal Ca + levels control the nociceptive state and that opioids, both endogenous and exogenous, exert their main effects via changes in Ca + disposition. 

Endogenous and exogenous alkaloids in shrimp, crabs, and barnacles are not studied. They probably are interesting animals from an evolutional point of view, and their chemistry research could lead to a new alkaloid discoveries. Lobsters have a low concentration endogenous opiate alkaloids in their body. These alkaloids are known to modify the channels and working on the nervous system. ... 

Exogenously administered substances are not the only agents which might interfere with a receptor binding assay. For example, opiate receptor binding as a radioreceptor assay for morphine would appear to be a relatively specific procedure since only opiates can interfere with the attachment to this receptor site. However, the discovery of endogenous opioid peptides makes the morphine assay less feasible with brain tissue because of the potential for these substances to be present in the tissue extracts. 

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