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Zheng Zhang, Ningli Wang, Beijing intracranial and intra-ocular pressure study; Axonal Transport in the Rat Optic Nerve Following Short-Term Reduction in Cerebrospinal Fluid Pressure or Elevation in Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4134.
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To examine the influence of short-term reduction in cerebrospinal fluid pressure (CSFP) as compared to short-term elevation in intraocular pressure (IOP) on axonal transport.
The study included 111 adult Sprague-Dawley rats. For six hours, IOP was elevated to 40mmHg (IOP40-study-group) (n=27,right eyes), IOP was increased to a value of 25mmHg below the mean blood pressure (“PP25-study-group”) (n=27,right eyes), or cerebrospinal fluid pressure was reduced by continuous aspiration of cerebrospinal fluid (“Low-CSFP-study-group”) (n=27). A “sham control group” (with a trocar in cisterna magna without cerebrospinal fluid release) included 24 rats. The left eyes of the IOP40-study-group and PP25-study-group served as additional “control group”. The orthograde axonal transport was examined by intravitreally injected rhodamine-ß-isothiocyanate, the retrograde axoplasmic flow was assessed by fluorogold injected into the superior colliculi.
At 24hours after baseline, the intensity of RITC staining of the optic nerve was significantly (P<0.05) lower in the IOP40-study-group, PP25-study-group and Low-CSFP-study-group than in the control groups. At six hours after the fluorogold injection, fluorogold fluorescence was significantly lower in the IOP40-study-group, the PP25-study-group and the Low-CSFP-study-group than in the control groups. At 5 days after baseline, fluorogold fluorescence no longer differed significantly between the IOP40-study-group or the Low-CSFP-study-group and the control groups.
Both, short-term lowering of CSFP and short-term rise in IOP, were associated with a disturbance of both the orthograde and retrograde axonal transport. The finding supports the notion of an association between abnormally low CSFP and optic nerve damage.
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