title: Influence of external light conditions on norepinephrine levels in organs innervated by sympathetic nerves from different levels.
abstract: Rat tissues receiving their sympathetic innervation from different levels were studied for changes in their norepinephrine level after maintaining the animals for 2 weeks under various lighting conditions. Constant darkness resulted in a doubling of the norepinephrine concentration in iris and a significant increase also in the pia-arachnoid when compared to the tissues from animals kept in alternating light/darkness conditions. Also continuous light gave higher norepinephrine concentrations in the pia-arachnoid. None of the light conditions studied affected cardiac norepinephrine. Norepinephrine levels in vas deferens were reduced after constant light and increased after constant darkness, compared to light/dark conditions. It is concluded that norepinephrine only in tissues innervated from the superior cervical sympathetic ganglia is influenced by external light stimuli, and that the norepinephrine changes in vas deferens are secondary effects of the hormonal alterations produced by continuous light and darkness, respectively, and affecting the entire reproductive tract.
mesh_terms: D000320:Adrenergic Fibers / Q000033:anatomy & histology*; D000818:Animals; D001158:Arteries / Q000294:innervation; D002940:Circadian Rhythm; D005728:Ganglia, Sympathetic / Q000033:anatomy & histology*; D006321:Heart / Q000294:innervation; D007498:Iris / Q000294:innervation; D008027:Light; D008297:Male; D008856:Microscopy, Fluorescence; D009638:Norepinephrine / Q000378:metabolism*; D010841:Pia Mater / Q000098:blood supply; D051381:Rats; D014649:Vas Deferens / Q000294:innervation
chemical_list: D009638:Norepinephrine