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Comparison of the effects of adrenergic agonists and α‐, β 1 ‐, β 2 ‐antagonists on the intraocular pressure and adenylate cyclase activity in the ciliary processes of the rabbit
Author(s) -
Palkama Arto,
Uusitalo Hannu,
Raij Kari,
Uusitalo Risto
Publication year - 1985
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1985.tb05206.x
Subject(s) - timolol , intraocular pressure , labetalol , cyclase , adenylate kinase , endocrinology , adrenergic , chemistry , medicine , agonist , metoprolol , adrenergic agonist , acebutolol , pharmacology , propranolol , blood pressure , receptor , ophthalmology
. The hypotensive effect of different adrenergic agonists and antogonists were screened both in normo‐ and hypertensive rabbit eyes. The drugs were applicated topically and intraocular pressure (IOP) was monitored constantly with a manometric method. Subsequently the inhibitory effect of the antagonists on isoproterenol‐stimulated adenylate cyclase activity in the ciliary processes was analyzed in vitro. In normotensive eyes agonist isoproterenol (β) and antagonists labetalol (αβ), metoprolol (β 1 ) and acebutolol (β 1 ) decreased signi‐ *** ficantly IOP. In hypertensive eyes only isoproterenol and labetalol decrease IOP markedly. Timolol (β) did not decrease IOP, although it inhibited adenylate cyclase activity as actively as labetlol. The other antagonists showed no inhibitory effect on in this respect. The results indicated that α‐activity (labetalol, αβ) seems to potentiate the β‐activity (timolol, β) in decreasing IOP. Whether this α‐effect is a presynaptic effect (adrenergic denervation destroys it) is not yet clear. Similarly the β 1 ‐effect (metoprolol), without affecting adenylate cyclase activity, decreased IOP as well. This might be due to pre‐synaptic release of endogenous transmitter(s) which in turn stimulate post‐synaptic adenylate cyclase and induce the decreased IOP. Besides this, the possible role of blood vessels and CNS must also be kept in mind.