Mu Receptors

Morphine and most clinical drugs act though the mu opiate receptors, making these receptors particularly important. Morphine has many actions, including analgesia, respiratory depression, and constipation. Early studies raised the possibility that these actions may be mediated though different subtypes of mu opioid receptors based on results using highly selective opioid antagonists. Antagonists have been developed that selectively block morphine analgesia without influencing respiratory depression and the inhibition of gastrointestinal transit. Another antagonist has also been reported that can reverse the actions of heroin without interfering with those of morphine. Thus, there is extensive pharmacological evidence for multiple subtypes of mu receptors.

Figure 3 Structure of G protein receptors. G protein-coupled receptors span the cell membrane seven times, with the amino terminus located extracellularly and the carboxy terminus inside the cell. They are coupled to G proteins, which are composed of three subunits (a, b, and g) and located on the inside surface of the cell. When the receptor is activated, it changes the G proteins, which then influence transduction systems.

Figure 3 Structure of G protein receptors. G protein-coupled receptors span the cell membrane seven times, with the amino terminus located extracellularly and the carboxy terminus inside the cell. They are coupled to G proteins, which are composed of three subunits (a, b, and g) and located on the inside surface of the cell. When the receptor is activated, it changes the G proteins, which then influence transduction systems.

Recently, a mu opioid receptor gene has been identified, MOR-1 (Fig. 4). Additional cloning work has isolated seven different splice variants of this gene, implying the existence of at least seven different mu opioid receptor subtypes at the molecular level. Thus, the molecular biological approaches have uncovered far more mu receptor subtypes than even suggested from pharmacological studies. Correlating these variants with specific opioid actions is not simple. We know that a major disruption of the MOR-1 gene eliminates all mu analgesia. However, more subtle disruptions of the gene leading to the elimination of only some MOR-1 variants block the analgesic actions of some, but not all, mu analgesics. At this point, it appears that most mu analgesics will activate more than one mu receptor subtype. Thus, differences among the mu analgesics may reflect differences in their pattern of receptor activation.

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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