An improved fixation method for guinea pig cochlear tissues.

The influence of different fixation methods and of various primary fixatives on the ultrastructural preservation of guinea pig cochlear tissues was investigated. No differences in fixation quality were observed between cochleas fixed by intravascular perfusion and cochleas fixed by intralabyrinthine perfusion. Tri-aldehyde primary fixation resulted, in contrast to other formulae investigated, in an excellent, uniform preservation of all cochlear tissues without obvious fixation artefacts. The influence of OSO4/K4Ru(CN)6- and OSO4/K4Fe(CN)6 postfixation was also tested. Cochlear tissues postfixed with OSO4/K4Ru(CN)6 or OSO4/K4Fe(CN)6 exhibited more cellular detail (e.g., membrane- and glycogen contrast) as compared to tissues postfixed with OSO4 alone. Tri-aldehyde primary fixation followed by OSO4/K4Ru(CN)6- or OSO4/K4Fe(CN)6 postfixation therefore is recommended as a multipurpose procedure for optimal preservation of labyrinthine tissues.