DO BETA-ADRENOCEPTORS AND SEROTONIN 5-HT1A RECEPTORS HAVE SIMILAR FUNCTIONS IN THE CONTROL OF INTRAOCULAR-PRESSURE IN THE RABBIT

Serotonin 5-HT1A-type and beta-adrenergic receptors have similar molec ular characteristics, which explains why certain substances like propr anolol have affinities for both receptor types. Activation of 5-HT1A r eceptors leads to a decrease in intracellular cAMP levels whereas the opposite occurs for beta-adrenergic receptors. Both 5-HT1A and beta-ad renergic receptors exist in the rabbit ciliary processes. Topical appl ication of the 5-HT1A agonist, 8-hydroxydipropylaminotetralin (8-OH-DP AT) reduces intraocular pressure (IOP). beta-Antagonists are also know n to reduce IOP. It is postulated that substances which have an affini ty for 5-HT1A and/or beta-adrenergic receptors and lead to a reduction in intracellular cAMP levels in the ciliary processes diminish IOP.