Claudia Giannetto1, Giuseppe Piccione, Elisabetta Giudice. 1. Department of Experimental Sciences and Applied Biotechnology, Laboratory of Veterinary Chronophysiology, Faculty of Veterinary Medicine, University of Messina, Polo Universitario dell'Annunziata, 98168 Messina, Italy.
Abstract
OBJECTIVE: To evaluate the circadian rhythms of intraocular pressure (IOP) and tear production in dog exposed to a natural photoperiod. ANIMALS STUDIED: We used 12 clinically healthy Beagles dog housed under natural photoperiod at indoor temperature and humidity. PROCEDURE: Intraocular pressure and Schirmer tear test (STT) I were measured every 4 h over a 48-h period in both eyes in each animal. Statistical analysis of the data was performed by one-way repeated-measures anova, Student's t-test, and single cosinor method. RESULTS: On each day, there was a highly significant effect of time on both parameters. A statistically significant difference of STT I values was observed comparing left and right eyes (P < 0.0001). Robust daily rhythms were observed for both parameters, IOP values showed diurnal acrophase (left eye: 09:33 +/- 00:50 h; right eye: 09:25 +/- 00:22 h), while STT I values showed nocturnal acrophase (left eye: 20:27 +/- 00:46 h; right eye: 20:00 +/- 00:05 h). CONCLUSION: This study has demonstrated circadian rhythms in both IOP and STT I.
OBJECTIVE: To evaluate the circadian rhythms of intraocular pressure (IOP) and tear production in dog exposed to a natural photoperiod. ANIMALS STUDIED: We used 12 clinically healthy Beagles dog housed under natural photoperiod at indoor temperature and humidity. PROCEDURE: Intraocular pressure and Schirmer tear test (STT) I were measured every 4 h over a 48-h period in both eyes in each animal. Statistical analysis of the data was performed by one-way repeated-measures anova, Student's t-test, and single cosinor method. RESULTS: On each day, there was a highly significant effect of time on both parameters. A statistically significant difference of STT I values was observed comparing left and right eyes (P < 0.0001). Robust daily rhythms were observed for both parameters, IOP values showed diurnal acrophase (left eye: 09:33 +/- 00:50 h; right eye: 09:25 +/- 00:22 h), while STT I values showed nocturnal acrophase (left eye: 20:27 +/- 00:46 h; right eye: 20:00 +/- 00:05 h). CONCLUSION: This study has demonstrated circadian rhythms in both IOP and STT I.
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