Related Experiment Video
Updated: Jun 28, 2026

Isolation of Retinal Arterioles for Ex Vivo Cell Physiology Studies
Published on: July 14, 2018
Adenosine enhances the relaxing influence of retinal tissue
Nele Maenhaut1, Koen Boussery, Christophe Delaey
1Department of Pharmacology, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
Abstract:
Retinal tissue from different species continuously releases an as yet unidentified retinal relaxing factor (RRF) lowering tone of isolated arteries. The potential influence of adenosine on this relaxing influence was investigated using isometric tension recording of different isolated arteries. The presence of bovine retinal tissue or rat retinal tissue enhanced the vasorelaxing effect of adenosine on isolated bovine retinal artery. In isolated rat carotid artery adenosine elicited no relaxation. However, a small relaxation is observed in the presence of rat retinal tissue, but not in the presence of porcine retina. The fact that adenosine potentiates the effect of rat retinal tissue but not that of a similar piece of porcine retinal tissue indicates species differences. Neither a NO-synthase inhibitor (nitro-L-arginine, 0.1mM), a cyclooxygenase inhibitor (indomethacin, 10 microM) or an epoxygenase inhibitor (miconazole, 10 microM) influenced the enhanced vasodilating effect of adenosine on bovine retinal arteries in the presence of bovine retinal tissue. On the other hand, when the retinal arteries were contracted with 120 mM K(+), adenosine no longer induced relaxation of the preparation with bovine retinal tissue. This is in line with the concept that adenosine enhances the influence of RRF. Also, the fact that rat carotid artery is less sensitive to RRF than bovine retinal artery - corresponding with a less enhanced adenosine response in rat carotid artery - is in line with the potential involvement of the RRF in the enhanced adenosine response. However, experiments using a bioassay setup for RRF gave no evidence for an increased RRF-release from the retina, nor for an increased RRF-sensitivity of the retinal artery in the presence of adenosine. In conclusion, our findings indicate that adenosine potentiates the relaxing influence of bovine and rat retinal tissue. This effect is species dependent as it is not seen with porcine retinal tissue. Neither NO, cyclooxygenase metabolites or epoxyeicosatrienoic acids seem to be involved in this enhanced vasorelaxing response. The involvement of the RRF cannot be excluded.
Related Concept Videos
Adrenergic Receptors: ɑ Subtype
Adrenaline ≥ Noradrenaline >> Isoprenaline
α-adrenoceptors are further divided into α1 and α2-adrenoceptors.
α1-Adrenoceptors: These receptors are located postsynaptically on the effector organs and cause constriction of smooth muscle mediated by activation of phospholipase C—inositol-1,4,5-trisphosphate...
Adrenergic Receptors: β Subtype
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors have equal affinities for...
Indirect-Acting Cholinergic Agonists: Pharmacological Actions
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...
Direct-Acting Cholinergic Agonists: Pharmacological Actions
Adrenergic Receptors (Adrenoceptors): Classification
α-Adrenoceptors
α-Adrenoceptors are classified into two main subtypes: α1 and α2. The α1 adrenoceptors, which are found on postsynaptic...
Adrenergic Agonists: Direct-Acting Agents
These agents can be classified...

