Functional role of a1-adrenoceptor subtypes in murine ophthalmic arteries.

Investigative Ophthalmology & Visual Science

PubMedID: 21613371

Gericke A, Kordasz ML, Steege A, Sanbe A, Goloborodko E, Vetter JM, Patzak A, Pfeiffer N. Functional role of a1-adrenoceptor subtypes in murine ophthalmic arteries. Invest Ophthalmol Vis Sci. 2011;52(7):4795-9.
PURPOSE
To identify the a(1)-adrenoceptor (a(1)-AR) subtypes mediating vascular adrenergic responses in murine ophthalmic arteries.

METHODS
Expression of mRNA was quantified for individual a(1)-AR subtypes in murine ophthalmic arteries using real-time PCR. To assess the functional relevance of a(1)-ARs for mediating vascular responses, ophthalmic arteries from mice deficient in one of the three a(1)-AR subtypes (a(1A)-AR(-/-), a(1B)-AR(-/-), and a(1D)-AR(-/-), respectively) and wild-type controls were isolated, cannulated with micropipettes, and pressurized. Changes in luminal artery diameter in response to the a(1)-AR agonist phenylephrine, the sympathetic transmitter noradrenaline, and to the nonadrenergic vasoconstrictor arginine vasopressin (AVP) were measured by video microscopy.

RESULTS
Using real-time PCR, mRNA for all three a(1)-AR subtypes was detected in ophthalmic arteries from wild-type mice. In functional studies, phenylephrine and noradrenaline produced dose-dependent constriction of ophthalmic arteries that was similar in wild-type, a(1B)-AR(-/-), and a(1D)-AR(-/-) mice. Strikingly, responses to phenylephrine and noradrenaline were almost completely abolished in a(1A)-AR(-/-) mice. In contrast, the nonadrenergic agonist AVP produced dose-dependent vasoconstrictor responses that did not differ between any of the mouse genotypes tested.

CONCLUSIONS
These findings provide evidence that the a(1A)-AR subtype mediates adrenergic vasoconstriction in murine ophthalmic arteries.