guanosine-5--o-(3-thiotriphosphate) and Ocular-Hypertension

To apply a multidisciplinary approach to the identification and pharmacological characterization of the serotonin (5HT) receptors that mediate functional responses in human trabecular meshwork (h-TM) cells. To correlate in vitro findings with intraocular pressure (IOP) changes in conscious ocular hypertensive cynomolgus monkeys.. Documented methods were used, including reverse transcription-polymerase chain reaction (RT-PCR), phosphoinositide (PI) turnover, and intracellular Ca2+ ([Ca2+]i) mobilization. IOP was measured using standard applanation pneumatonometry.. h-TM cells expressed robust mRNA signals for 5HT2A and 5HT2B receptors. 5HT and its analogues stimulated PI turnover and [Ca2+]i mobilization in h-TM cells from multiple donors (20/24 donors' TM cells responded). The agonist potencies (EC50) of compounds in mobilizing [Ca2+]i were (nM): 5-methoxy tryptamine, 8 +/- 4; (R)-DOI, 18 +/- 6; alpha-methyl-5HT, 22 +/- 3; 5HT, 40 +/- 7; 5-methoxy-dimethyl tryptamine, 64 +/- 27; and BW-723C86, 1213 +/- 210. These effects were potently blocked by the 5HT2A-receptor-selective antagonist, M-100907 (Ki = 1 +/- 0.3 nM), but weakly by antagonists of 5HT2B and 5HT2C receptors. Only 5HT2 receptor agonists such as (R)-DOI (300 microg lowered IOP 34.4% from baseline of 38.2 mm Hg; P < 0.001) and alpha-methyl-5HT (250 microg lowered IOP 30.8% from baseline of 41.8 mm Hg; P < 0.001) lowered IOP in ocular hypertensive cynomolgus monkeys.. Strong signals for 5HT2A and 5HT2B receptor mRNAs were detected in h-TM cells. The receptors that coupled to PI hydrolysis and [Ca2+]i mobilization in h-TM cells were the 5HT2A receptor subtype, which also significantly lowered IOP in a primate model. These receptors may mediate the ocular hypotensive actions of 5HT2A agonists.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Amphetamines; Animals; Calcium; Child; Child, Preschool; CHO Cells; Cricetinae; Cricetulus; Female; Gene Expression Regulation; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Infant; Inositol Phosphates; Intraocular Pressure; Macaca fascicularis; Male; Middle Aged; Ocular Hypertension; Receptor, Serotonin, 5-HT2A; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Serotonin Receptor Agonists; Trabecular Meshwork; Transfection