Loss of Circadian Rhythm of IOP Following Cervical Ganglionectomy in Rats

Abstract

 

Purpose:

 

To investigate whether ocular sympathetic activities involvein the circadian rhythm of intraocular pressure(IOP) in therat.

 

Methods:

 

Sprague-Dawley rats were entrained in a daily 12-hour light/12-hourdark cycle for 3 weeks (n=9). Circadian time 6 to 18 o’clockwas the subjective light phase. We measured the IOP of botheyes every 4 hr with Tonopen-XL tonometer in awake state duringthe circadian 24 hrs. The average of repeated 10 values of IOPwas calculated at each time. Then unilateral cervical ganglionectomywas done on these rats (n=9). Sympathetic innervation to theeye was destroyed by surgical removal of the right superiorcervical ganglion (superior cervical ganglionectomy; SCGx).We measured the IOPs at postoperative 1, 2, 3 and 4 weeks inthe same way during the same circadian cycle. Statistical analysiswas done by T-test and F-test(one way ANOVA) using SPSS 12.0processor. All surgical procedures were approved by InstitutionalAnimalCare and Use Committee at Gyeongsang National Universityand conformed to the ARVO statement for the Use of Animals inOphthalmic and Vision Research.

 

Results:

 

Rat has a circadian rhythm of IOP which was higher in the darkthan in the light. But, after cervical ganglionectomy the circadianrhythm of IOP was disappeared and the change of circadian rhythmwas maintained until 4 weeks later.

 

Conclusions:

 

Ocular sympathetic activities may play a role in the circadianrhythm of IOP in the rat.  

 

 

Keywords: circadian rhythms • intraocular pressure