Photoreceptors are preferentially affected in the rat retina following permanent occlusion of the carotid arteries.

Carotid artery occlusion (two vessel occlusion; 2-VO) for 3 or 9 months causes a suppression of the electroretinogram. However, after 3 months the retinal morphology appears unaffected judging from the localisation of GABA, ChAT, alpha PKC, Thy-1 and GFAP immunoreactivities. Moreover, no difference in NMDA-R1, opsin or Thy-1 mRNA levels were detected. In contrast, after 9 months 2-VO photoreceptor degeneration occurred as indicated by thinning of the outer nuclear layer and reduced Ret-P1 immunoreactivity. All other immunoreactivities appeared normal. These findings were supported by analysis of retinal mRNA levels. We conclude that the major effect of prolonged 2-VO is photoreceptor degeneration.