Posted by Scott L. Schofield on December 28, 1999, at 9:50:21
In reply to Re: New Offshore Supplier! Mirapex available!, posted by Bruce on December 20, 1999, at 7:51:31
> At any rate, Requip is available, and has a similar action to Mirapex.What are the generic names for Requip and Mirapex?
> Interestingly, both drugs now have a warning of somnolence (which apparently happens to a large percentage of users) - that is odd considering they are dopamine agonists. You'd think they'd be energizing. I may yet try amisulpride.
This effect is seen quite often when low doses of some direct dopamine agonists are used. Presynaptic dopamine autoreceptors tend to be “stronger” than the postsynaptic receptors at attracting the neurotransmitter. These autoreceptors, when stimulated by the attachment of a natural neurotransmitter molecule or a drug that mimics it, tells the presynaptic neuron to “power-down” by decreasing the amount of dopamine being manufactured as well as releasing smaller amounts of it. At low dosages, a greater ratio of the stronger presynaptic autoreceptors are stimiulated as compared with those that are postsynaptic. The consequence of this is a reduction in the number of postsynaptic dopamine neurons firing and a resultant state of sedation. At higher dosages, basically all of the receptors are stimulated, including the postsynaptic ones that cause the stimulation otherwise associated with these drugs.
Amisulpiride works exactly in reverse. It is a dopamine receptor antagonist. It sticks to the receptors without stimulating them. It therefore blocks the receptor from capturing the dopamine that would otherwise stimulate it. At low dosages, more presynaptic autoreceptors are blocked than are postsynaptic, so the first neuron is convinced that it needs to manufacture and release more dopamine while there are still enough open receptors on the second neuron to be stimulated by it. This is what may account for its antidepressant effects. At higher dosages, the receptors of the postsynaptic neuron are blocked, leading to its inhibition. This is what is thought to be responsible for its anti-psychotic properties and why it has been used for schizophrenia.
- Scott
poster:Scott L. Schofield
thread:16940
URL: http://www.dr-bob.org/babble/19991212/msgs/17622.html