The aim of the study was to determine whether memantine
could slow down the changes seen in the rabbit and rat
retina following ischemia/reperfusion. A “suction
cup procedure,” which raises the intraocular pressure,
was used to give an ischemic insult to the rabbit retina.
The electroretinogram was recorded before ischemia and
after 2 days of reperfusion. Memantine or saline (10 μl)
was injected into the eye before ischemia. Immunohistochemistry
was used to study the effect of ischemia/reperfusion on
the GABA, ChAT, and αPKC immunoreactivities. Ischemia/reperfusion
injury to the rat retina was induced by raising the intraocular
pressure above the systolic blood pressure for 60 min,
followed by reperfusion of 3–14 days. Memantine (5
mg/kg) or saline was injected i.p. at the onset of ischemia
or reperfusion. Immunohistochemistry was used to study
the effect of ischemia/reperfusion on the ChAT, αPKC,
and Thy-1 immunoreactivities. In addition, morphometric
analysis was carried out to determine the effects of ischemia/reperfusion
on the thickness of the retina. Ischemia for 75 min caused
a change in the nature of the normal GABA and ChAT immunoreactivities
in the rabbit retina and a reduction in the b-wave
of the electroretinogram. When memantine was injected into
the vitreous humour at the onset of an ischemic insult,
the changes in the GABA and ChAT immunoreactivities were
reduced and the recovery of the reduced b-wave
of the electroretinogram after 2 days reperfusion was enhanced
significantly. Ischemia for 60 min followed by 3 days reperfusion
showed a clear change in ChAT immunoreactivity in the rat
retina. The Thy-1 immunoreactivity was only clearly altered
after a reperfusion period of 7 days. Moreover, a measurable
change in the thickness of the inner retinal layers was
detected after 14 days of reperfusion. When given at the
onset of ischemia, memantine counteracted the effect of
ischemia/reperfusion to varying degrees. However, when
memantine was given at the onset of the reperfusion this
was not the case. The combined data show that a single
injection of memantine given i.p. or intravitreally will
protect the retina from a subsequent ischemic insult.