Stimulation of β1- and β2-adrenoceptors dilates retinal blood vessels in rats

Abstract

Our previous studies have demonstrated that adrenaline dilates rat retinal arterioles by stimulating propranolol-sensitive β-adrenoceptors and β-adrenoceptors, and selective stimulation of β- or β-adrenoceptors causes retinal vasodilator responses. In the present study, we compared the effects of β- and β-adrenoceptor stimulation on rat retinal arterioles in vivo. Rat ocular fundus images were captured using an original high-resolution digital fundus camera. Diameters of retinal arterioles contained in the images were measured. Systemic blood pressure and heart rate were recorded continuously. Denopamine, a β-adrenoceptor agonist, increased the diameter of retinal arterioles and heart rate, and produced a small but statistically insignificant decrease in mean arterial pressure. CGP20712A, a β-adrenoceptor antagonist, but not ICI118551, a β-adrenoceptor antagonist, significantly prevented denopamine-induced retinal vasodilator and heart rate responses. Salbutamol, a β-adrenoceptor agonist, increased the diameter of retinal arterioles and decreased mean arterial pressure without significantly changing heart rate. The effects of salbutamol were significantly prevented by ICI118551, but not by CGP20712A. These results suggest that stimulation of β- and β-adrenoceptors dilates retinal blood vessels and indicate that all three β-adrenoceptor subtypes (β, β, and β) may be involved in the retinal vasodilator response to adrenaline in rats.

The effect of dobutamine on ocular blood flow of healthy adults: A 3D pseudocontinuous aterial spin labelling study

“…Accordingly, the changes of OBF may depend on nervous stimulation, we hypothesize neural component is involved in the regulatory mechanism. Also, based on the widespread distribution of β -ARS in retinal vessels and neuroretinas, β -ARS is believed to play an important role in retinal vascular and neuronal functions (Ruan et al, 2020; Mori et al, 2017 ) provide the evidence that stimulation of β-adrenoceptors leads to dilation of small arteries in the rat retina, thereby increasing retinal blood flow. Dobutamine has the capacity to stimulate β-adrenoceptors in the cardiovascular system, may also to dilates retinal blood vessels of human.…”

“…Cannabinoid receptors are present in and around the blood vessels of the eye, so oral intake of 5 mg dronabinol induced a significant increase in total retinal blood flow (Hommer et al, 2021). However, these drugs usually have certain side effects, including flushing, headache, nasal congestion, gastric discomfort and allergic reactions (Moreira et al, 2000;Hoff Roland and Nergard, 2012). Therefore, there is no standard treatment protocol to increase OBF.…”

The Role of Adrenoceptors in the Retina

“…Xamoterol, a β 1 -AR agonist, attenuated iNOS expression in human retinal endothelial cells grown in high glucose medium [191]. Studies by Mori et al have demonstrated that stimulation of β 1 -, β 2 -, and β 3 -ARs can cause dilation of retinal arterioles in rats, thus, increasing retinal blood flow [207,208]. Moreover, the latest study by Mori et al reported that retinal vasodilation by β 2 -AR stimulation is mediated via a G i protein by activation of large-conductance Ca 2+ -activated K + channels [209].…”