Responses of imidalolines on bovine ciliary artery

H. Ishikawa, Duane Miller, P. N. Patil

Research output: Contribution to journalArticle

Abstract

Purpose. The present investigation represents a characterization of actions of numbers of imidazolines on the segment of bovine ciliary artery which is partly responsible for maintaining the ocular blood flow. Methods and Results. A segment of bovine ciliary artery was mounted in an organ bath and tension changes were recorded. Norepinephrine (NE), oxymetazoline (OMZ) and phenylephrine caused nonlinear biphasic contraction in this tissue. When KCl maxima was considered to be 100%, the responses of OMZ and NE was 55% and 45%, respectively. Based on ED 50 values of the first component response, the rank order of potency was OMZ, 1 > NE, 1/7 > phenylephrine, 1/72. At equipotent doses of NE and OMZ, the t 1/2 duration of response of the latter agonist was 43 times greater than that of the former agonist. At the interval of three hours the agonist responses were 95% reproducible. Naphazoline, tetrahydrozoline and para-aminoclonidine did not produce significant contraction of the blood vessel, but antagonized the action of agonists. As compared to that of NE, naphazoline was relatively selective in blocking responses of OMZ. Phentolamine blocking action of NE was greater than that of OMZ. The vascular pK B of prazosin-NE interaction was 8.3. The responses of OMZ were totally resistant to block by 1 μM of prazosin. Nifedipine at 100 nM blocked the second component of the responses of OMZ. Conclusions. These results indicate that ciliary artery contains a subtype of α-adrenoceptors (α 1L) with low sensitivity to prazosin. The tissue also contains a unique OMZ sensitive site or imidazoline receptors which is resistant to block by prazosin.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996

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Oxymetazoline
Ciliary Arteries
Norepinephrine
Prazosin
Naphazoline
Phenylephrine
Blood Vessels
Imidazoline Receptors
Imidazolines
Phentolamine
Nifedipine
Baths
Adrenergic Receptors

All Science Journal Classification (ASJC) codes

  • Ophthalmology

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Responses of imidalolines on bovine ciliary artery. / Ishikawa, H.; Miller, Duane; Patil, P. N.

In: Investigative Ophthalmology and Visual Science, Vol. 37, No. 3, 15.02.1996.

Research output: Contribution to journalArticle

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