Localization of prostanoid receptors and cyclo-oxygenase enzymes in guinea pig and human cochlea

Endogenous production of prostaglandins has been demonstrated in the cochlea, but no information is available on the distribution of the cyclo-oxygenase (COX) enzymes, or prostanoid receptors in the cochlea. The purpose of the present study was to investigate the localization of the FP, EP(1) and EP(3) prostanoid receptors as well as the COX-1 and COX-2 enzymes in the cochlea of guinea pig and man. Cochleas were processed for immunohistochemistry using routine techniques. Appropriate controls comprised incubation with specific blocking peptides, or incubation without primary antibodies. Both in guinea pig and man the FP prostanoid receptor was abundantly distributed in the cochlea, e.g., in stria vascularis, the spiral ligament, spiral ganglion, and organ of Corti. The immunohistochemical staining of the EP(1) and EP(3) receptors in the same structures was significantly weaker and sometimes lacking altogether (e.g., EP(3) receptor in human cochlea). Weak, but mostly consistent immunostaining of the COX-1 enzyme was found in the cochlear structures. The COX-2 enzyme appeared to be lacking. The abundant distribution of the FP receptor in several important cochlear structures both in guinea pig and man suggests a physiological function for PGF(2alpha) in the cochlea. The COX-1 enzyme seems to be constitutively expressed in the cochlea in contrast to COX-2.