Preservation of glutamate immunoreactivity and ischemic change in photoreceptor inner segments in the retina after different protocols of perfusion fixation.

Aim: The present study investigates whether glutamate immunoreactivity (IR) in the cat outer retina, which is devoid of blood vessels, can be well preserved by perfusion fixation.
Methods: Adult cats were perfused intracardially for 1, 5, 10, 15 and 30 min with physiological saline and were subsequently perfused with a mixture of 1% glutaraldehyde and 4% formaldehyde. After the fixation, the retinas were immunocytochemically examined.
Results: The photoreceptor inner segments in the retina, which was perfused by saline for 1 and 5 min prior to fixation, showed no glutamate IR. However, those in the retina which was perfused by saline for 10 min showed moderate glutamate IR as found in the retina fixed by immersion. The glutamate IR in the inner segments decreased with a saline perfusion of more than 10 min.
Conclusions: Perfusion fixation can well preserve glutamate IR even in the outer retina including the inner segments.