α 1 adrenoceptor

from Wikipedia, the free encyclopedia

The α 1 -adrenoceptors are G q / 11 -protein-coupled receptors that are activated by the signaling substances adrenaline and noradrenaline . Based on their pharmacological properties, they are divided into four subtypes: α 1A , α 1B , α 1D and “α 1L ”. While the first three subtypes also embody independent receptors at the genomic level , the “α 1L ” adrenoceptor appears to be just a conformational variant of the α 1A subtype.

Occurrence and function

α 1 -adrenoceptors occur in high density in the central nervous system , in the sympathetically innervated tissue, in the salivary glands , especially in the cardiovascular system and in the urogenital tract and in the liver . The stimulation of smooth muscle α 1 -adrenoceptors in blood vessels (subtypes A, B and D) leads to an increase in blood pressure caused by vasoconstriction . A contraction of the organs of the urogenital tract (e.g. prostate and internal sphincter muscle ) is mediated by smooth muscle α 1A / L adrenoceptors and thus leads, for example, to urinary retention . Their role in the central nervous system, on the other hand, is largely unexplored.

pharmacology

α 1 -adrenoceptor agonists : α 1 -adrenoceptor agonists excite sympathetic α 1 -adrenoceptors. They are used systemically or topically (locally) for vasoconstriction:

α 1 -adrenoceptor antagonists (subgroup of alpha blockers ): α 1 -adrenoceptor antagonists inhibit the effects caused by adrenaline and noradrenaline and are therefore used therapeutically:

Pharmacological properties and function of the α 1 -adrenoceptor subtypes
property α 1A α 1B α 1D 1L "
Agonist Adrenaline , noradrenaline , phenylephrine
Selective agonist A-61603, oxymetazoline - Buspirone A-61603
antagonist Prazosin , Doxazosin , Terazosin , Alfuzosin , Urapidil , Sertralin , Tamsulosin
Selective antagonist 5-methylurapidil , B8805-033, SNAP 5089, RS-17053 Chloroethylclonidine , L-765314 BMY 7378, MDL 73005EF -
function Blood pressure regulation Blood pressure regulation Blood pressure regulation (?) Prostate contraction

Signal transduction

Through the activation of phospholipase C, α 1 -receptors lead to the formation of the second messenger inositol trisphosphate (IP 3 ) and diacylglycerol (DAG).

IP 3 releases Ca 2+ from the endoplasmic reticulum (ER), which u. a. binds to calmodulin and troponin . DAG influences the activity of other proteins by activating protein kinase C.

literature

  • S. Guimarães & D. Moura: Vascular Adrenoceptors: An Update. In: Pharmacol. Rev. 53/2001, pp. 319-356.
  • JR Docherty: Subtypes of functional α 1 - and α 2 -adrenoceptors. In: Eur. J. Pharmacol. 361/1998, pp. 1-15.