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  • Topically applied caffeine induces miosis in the ketamine/xylazine anesthetized rat.

Topically applied caffeine induces miosis in the ketamine/xylazine anesthetized rat.

Experimental eye research (2014-08-12)
Martin Kronschläger, Zhaohua Yu, Nooshin Talebizadeh, Linda Maren Meyer, Per Söderberg
ABSTRACT

The aim of the present study was to examine if topically applied caffeine influences pupil size in ketamine/xylazine anesthetized animals. Two experiments were carried out. In the first experiment, caffeine was topically applied to one of the eyes of 10 ketamine/xylazine anesthetized animals, while vehicle only was topically applied to the contralateral eye. In the second experiment, caffeine was topically applied to both eyes in one group of 10 ketamine/xylazine anesthetized rats, while in another group both eyes vehicle only was topically applied to both eyes. In both experiments pupil diameter was measured at 0, 10, 20, 40 and 60 min after topical application. In three of the animals, the pupil was dilated with tropicamide 5 mg/ml at 60 min after the topical application of caffeine and the pupil diameter was measured. The first experiment showed a relative miosis in caffeine treated eyes as compared to the vehicle treated eye, that changed over time. The second experiment in line with the first experiment, also showed that topically applied caffeine causes a relative miosis as compared to vehicle only that changes over time. Eyes treated with caffeine reacted with quick dilatation after tropicamide application. Topical caffeine antagonizes ketamine/xylazine anesthesia induced mydriasis in a time dependent manner.

MATERIALS
Product Number
Brand
Product Description

Supelco
Caffeine solution, 1.0 mg/mL in methanol, ampule of 1 mL, certified reference material, Cerilliant®
Caffeine for system suitability, European Pharmacopoeia (EP) Reference Standard
Supelco
Melting point standard 235-237°C, analytical standard
Supelco
Caffeine solution, analytical standard, 1.0 mg/mL in methanol
Sigma-Aldrich
Caffeine, SAJ special grade, ≥98.5%
Supelco
Caffeine, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Caffeine Melting Point Standard, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
(±)-Ketamine hydrochloride, solid
Supelco
Caffeine, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
USP
Caffeine, United States Pharmacopeia (USP) Reference Standard
Supelco
Mettler-Toledo Calibration substance ME 18872, Caffeine, traceable to primary standards (LGC)
Sigma-Aldrich
Caffeine, powder, ReagentPlus®
Sigma-Aldrich
Caffeine, meets USP testing specifications, anhydrous
Sigma-Aldrich
Caffeine, BioXtra
USP
Caffeine melting point standard, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Caffeine, anhydrous, tested according to Ph. Eur.
Sigma-Aldrich
Caffeine, anhydrous, 99%, FCC, FG
Sigma-Aldrich
Caffeine, Sigma Reference Standard, vial of 250 mg
Supelco
Ketamine hydrochloride solution, 1.0 mg/mL in methanol (as free base), ampule of 1 mL, certified reference material, Cerilliant®
Caffeine, European Pharmacopoeia (EP) Reference Standard