Outflow facility in the monkey eye: effects of calcitonin gene-related peptide, cholecystokinin, galanin, substance P and capsaicin.
A study in cats has shown that intracameral injection of calcitonin gene-related peptide (CGRP) increases the outflow facility by four- to fivefold concomitant with a decrease in intra-ocular pressure (IOP). Since there are great differences in the anatomy of the aqueous outflow routes between cats and primates, we have examined the effects of CGRP in the cynomolgus monkey. The possible influence of the sensory neuropeptides cholecystokinin (CCK), galanin and substance P on the outflow facility and IOP were also investigated. Determinations were performed using a two-level constant-pressure procedure. At 40-60 min after intracameral injection of 3 micrograms CGRP the outflow facility was increased from 0.68 +/- 0.11 to 1.03 +/- 0.15 microliters min-1 mmHg-1 in the CGRP-treated eyes, and from 0.71 +/- 0.12 to 0.79 +/- 0.10 microliter min-1 mmHg-1 in the control eyes. The mean difference in increase was 0.27 +/- 0.06 microliter min-1 mmHg-1 (P less than 0.01, n = 7). During the experiments there was a small rise in the IOP. CGRP at a dose of 3 micrograms caused a small rise in aqueous humor protein concentration. An attempt to release endogenous CGRP with capsaicin did not result in an increased outflow facility. Three micrograms each of CCK, galanin and substance P had no significant effect on either the outflow facility or the IOP. A miosis was observed in the experiments with CCK in agreement with previous findings. CCK seems thus to cause contraction of the pupillary sphincter but does not influence the ciliary muscle sufficiently to cause a facility effect in the monkey eye.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Physiology and Medical Biophysics, University of Uppsala, Sweden.
B
B
Almegård
S E
SE
Andersson
D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology*; D002766:Cholecystokinin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D019004:Galanin; D007429:Intraocular Pressure / Q000187:drug effects; D008252:Macaca fascicularis; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D011680:Pupil / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology*; D013997:Time Factors
D009479:Neuropeptides; D010455:Peptides; D013373:Substance P; D019004:Galanin; D002766:Cholecystokinin; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin