surgical sympathectomy produces most of the retinal changes noted in the retina of an STZ-treated rat in a non-diabetic rat

Sympathectomy significantly increases gene and protein expression of iNOS, as well as levels of PGE2 and protein expression of PGE2-EP2 receptor subtype. Isoproterenol treatment for 6 h to human retinal endothelial cells grown in high glucose medium reduced iNOS protein expression, but had no effect on PGE2 levels or PGE2 receptor protein expression. iNOS expression was attenutated by stimulation with xamoterol, while BRL37344 had no effect, suggesting that the iNOS effects are mediated by beta1-adrenergic receptors. These results suggest that loss of sympathetic activity, as occurs in diabetes, results in an upregulation of iNOS and PGE2-EP2 receptor protein expression, as well as PGE2 levels. Isoproterenol stimulation of human retinal endothelial cells cultured in a hyperglycemic environment decreased iNOS expression with no change in PGE2 levels, suggesting that only iNOS expression is modulated by sympathetic neurotransmission in endothelial cells. Overall, these results further the idea that alterations in sympathetic neurotransmission may result in many of the changes noted in the retina of the STZ-treated rat.
http://www.ncbi.nlm.nih.gov/pubmed/17067575

Sympathectomy leading to an extracranial steal phenomenon

J Igloffstein and R Laas
J Neurol Neurosurg Psychiatry. 1983 August; 46(8): 768–773.
Unilateral cerebral infarcts were produced in the rat by ligation of one common carotid artery and subsequent exposure to carbon monoxide. The incidence and extension of brain infarcts was increased in animals with additional ipsilateral cervical preganglionic sympathectomy.Sympathectomy did not affect markedly the respiration and systemic circulation. The effect of sympathectomy was attributed to a cutaneous vasodilation, leading to an extracranial steal phenomenon.http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1027532