Opioid system receptor types

Propoxyphene is an agonist of opioid fi receptors. It is this opioid effect that is responsible for the central nervous system and respiratory depression seen in overdose. Both propoxyphene and norpropoxyphene are potent blockers of myocardial sodium channels, an effect identical to type lA antidysrhythmic agents. This myocardial sodium channel blockade may result in prolongation of the electrocardiogram QRS complex, arrhythmias, and cardiovascular depression seen in propoxyphene poisoning. 

Strong evidence indicates at least a familial pattern and perhaps a hereditary basis for some types of alcoholism ( 393). More recent data show that genotype accounts for approximately 33% of the overall variance in liability ( 394). In addition, specific neurocircuitry and neurochemical systems appear to be important in the etiology of alcoholism (395). Thus, positive reinforcement may be mediated by activation of g-aminobutyric acid (GABA) receptors, release of opioid peptides and dopamine, inhibition of glutamate receptors, and interactions with the 5-HT system. Furthermore, neurobehavioral effects of alcohol and their association with these various neurotransmitters serve as potential targets for novel drug therapies. 

Opioids is the common name for all compounds which have the same mode of action as the constituents of opium, the dried milky liquid of the poppy seed, Papaver somniferum (Brownstein, 1993). All opioids interact in biological systems with the same type of receptor, the so-called opioid receptor. 

The different types and subtypes of opioid receptors in the nervous system. The mu (p), kappa (k) and delta (8) subtype are designated by corresponding Greek letters. 

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