On Fri, 24 Oct 2003 18:39:45 GMT, "David Todtman"
<dtodtmanREMOVETHHIS at shaw.ca> wrote:
>It is very helpful to have your response.
>>I think you are correct about my need to get a more explicit text.
>>Can you note for me how a receptor is caused to be up-regulated or
>down-regulated? I would think that molecule/receptor binding is a 'digital'
>function. I.e., if the ligand molecule encounters a fitting receptor it
>either binds or does not. One cannot have a partial bind or a 'bigger
>bind.' Eh? Does the internal portion of the receptor, in up-regulation,
>release more of its chemical?
1. Any receptor-mediated mechanism might be modulated by co-factors
or by other cellular mechanisms (like other metabotropic receptor
events). In general though, you might think of it as a population
effect. If more (or fewer) are simultaneously activated or serially
activated, the internal effect can be modulated proportionately
>Also, back to the question of ionotropic vs metabotropic functions, is
>dopamine an example of a ligand that causes (mostly) metabotropic change?
Yes but DA has a number of different receptors which do different
>Again, the responses to my questions are very helpful to me.
> (This is interesting stuff.)