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Inverse Agonism at alpha(2)-adrenoceptors in Native Tissue

Inverse Agonism at alpha(2)-adrenoceptors in Native Tissue

L C Murrin, M E Gerety, H K Happe, D B Bylund

Eur J Pharmacol. 2000 Jun 16;398(2):185-91.

PMID: 10854829

Abstract:

Several alpha(2)-adrenoceptor antagonists have inverse agonist properties in cell culture systems, usually expressing high levels or a constitutively active form of alpha(2)-adrenoceptors. In characterizing the binding of alpha(2)-adrenoceptor agonists to rat brain tissue sections, we found that conditions known to alter agonist affinity for these receptors, particularly the addition of 100 microM GTP, altered the binding of the alpha(2)-adrenoceptor antagonist, [3H](1,4-benzodioxan-2-methoxy-2-yl)-2-imidazoline hydrochloride (RX821002). In further studies, we found that under our conditions [3H]RX821002 demonstrates inverse agonist properties at alpha(2)-adrenoceptors. This is the first demonstration of inverse agonism at alpha(2)-adrenoceptors in native tissue. We found that the alpha(2)-adrenoceptor antagonist, (2S,12bS)1', 3'-dimethylspiro(1,3,4,5',6,6',7,12b-octahydro-2H-benzo(b)fu ro(2, 3-a)quinazoline)-2,4'-pyrimidin-2'-one (MK-912), did not have clearly discernible inverse agonist properties and acted as a neutral antagonist in these studies. On the other hand, the antagonist rauwolscine actually displayed partial agonist properties in our studies. These findings indicate that the inverse agonist properties of alpha(2)-adrenoceptor antagonists can be demonstrated in native tissue, as well as in tissue culture, and they strengthen the idea that inverse agonist properties may be of physiological and pharmacological importance.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP109544458	RX 821002 hydrochloride		109544-45-8	Price

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