RESUMO
PURPOSE: We evaluated the structure, distribution and innervation of the extraocular pulley smooth muscle in the rat, a species with a less complex visuomotor repertoire than primates. METHODS: The adult Sprague-Dawley rat was perfused transcardially with physiological saline followed by 4% formalin. The rat orbit was dissected en bloc, then paraffin processed and serially sectioned for hematoxylin-eosin and Masson's trichrome stain. The distribution and innervation of the extraocular pulley smooth muscle was confirmed by immunohistochemistry with human smooth muscle (SM) alpha-actin, tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS). RESULTS: We found the pulley structure consist of focal condensations of eleastin and collagenous connective tissue in relationship to the rectus muscle in the equatorial Tenon's fascia. Especially, the pulley smooth muscle connected to medial rectus muscle was immunostained to TH and NOS. CONCLUSIONS: The data supports the presence of the extraocular pulley smooth muscle in the rat orbit supposing to have dopaminergic and nitroxidergic innervation.