Functional innervation of bovine ophthalmic artery

To investigate the functional innervation pattern in smooth muscle of bovine ophthalmic artery, we studied the effect of electrical stimulation and various drugs on the mechanical responses of this muscle using isometric tension recording methods. Electrical stimulation evoked phasic contractions which were abolished by guanethidine and tetrodotoxin (TTX), suggesting that the responses were neurogenic in origin. Phentolamine (10(-5) M) and 10(-5) M timolol did not affect this contractions, but 10(-5) M phentolamine and 10(-6) M prazosin markedly reduced the amplitude of contraction evoked by exogenously applied phenylephrine (10(-5) M). Electrical stimulation applied during sustained contraction evoked by 5-hydroxytryptamine in the presence of guanethidine and atropine evoked relaxation which was markedly suppressed by TTX. These results indicate that bovine ophthalmic artery is innervated by adrenergic nerve fibers, and an unidentified neurotransmitter, other than noradrenaline, may play an important role in the excitatory neuroeffector transmission, and that the tissue is also innervated by non-adrenergic non-cholinergic inhibitory nerve fibers.