Functional innervation of bovine ophthalmic artery

Dual effects of ATP on isolated arteries of the bovine eye

Although the presence of purinoreceptors has been shown in many human and animal arteries, there is few data yet about their role in the arteries of the eye. The purpose of the present study was to evaluate the effects of several agonists of purinoreceptors on isolated arteries of the bovine eye. Responses of isolated preparations of bovine ophthalmic (OA) and posterior ciliary arteries (PCA) to agonists of purinoreceptors (ATP, α,β-methylene-ATP-α,β-meATP, 2-methylthioATP-2meSATP, uridine-5'-triphosphate-UTP) as well as agonists of adreno-, cholino-, adenosine and histamine receptors were recorded by a standard organ bath method. ATP induced contractions of the intact vessels but caused relaxation of α,β-meATP-pretreated arteries. Contractile responses of PCA to high concentrations of ATP and α,β-meATP were significantly stronger than responses of OA, as well as relaxative responses to ATP and adenosine were significantly stronger in PCA than in OA. We suggest that there are several subtypes of functionally active purinoreceptors in both OA and PCA, although the potency of agonists of purinoreceptors to produce mechanical responses is higher in PCA than in OA. Purinoreceptors can be potential targets for new drugs, treating vascular pathology of the eye.

Increases in Central Retinal Artery Blood Flow in Humans Following Carotid Artery and Stellate Ganglion Irradiation with 0.6 to 1.6.MU.m Irradiation

The authors applied near-infrared low-level laser irradiation (LLLI) directed to the stellate ganglion (SG) and to the common carotid artery (CCA), and compared the effects on central retinal artery blood flow using color pulse Doppler sonography. In 10 healthy volunteers, LLLI (0.92 W, 1 : 1 duty cycle, 10 min) to both the SG and CCA significantly increased peak systolic blood velocity in the ophthalmic artery (p<0.001, each) and central retinal artery (p<0.001, each) without changes in vessel resistance. Irradiation to the CCA produced a stronger effect than that to the SG in the ophthalmic artery (p=0.007) and central retinal artery (p=0.031). These data suggest that LLLI to the SG or to the CCA is a useful therapy for increasing the retrobulbar blood flow, with irradiation directed to the CCA being more effective than that directed to the SG in clinical settings.

Actions of imidazolines on bovine ciliary artery

A segment of bovine ciliary artery exhibits nonlinear biphasic contractile responses to agonists. The maximal responses of oxymetazoline (OMZ) and norepinephrine (NE) were 55% and 45%, respectively (KCl = 100%). The relative potency comparison based on the ED50 of the first component of the dose-response curve was OMZ; 1 > NE; 1/7 > phenylephrine; 1/72. At equipotent doses of NE and OMZ, the t1/2 duration of response of the latter agonist was 43 times greater than that of the former and, after 3 hrs, responses were 95% reproducible. Naphazoline, tetrahydrozoline and para-aminoclonidine did not produce significant contraction of the blood vessel but did antagonize the action of the agonists. As compared to that of NE, naphazoline was selective in blocking responses of OMZ. Phentolamine blocking action of NE was greater than that of OMZ. Nifedipine, 100 nM, reduced the second component of OMZ response. Although the vascular action of NE was blocked by prazosin, the contractile action of OMZ was totally resistant to block by 1 microM of prazosin. These results indicate that ciliary artery contains a subtype of alpha-adrenoceptors (alpha 11) with low sensitivity to prazosin. The tissue also contains a unique OMZ sensitive site or imidazoline receptors which exhibit low affinity to alpha-adrenoceptor blockers.