Hearing Research, 43 (19~) 269-T'/2 Else,Aer H FJtRES O1312 Haircell forward and reverse transduction: Differential suppression and enhancement Atlyn E. Hubbard and David C. Mountain (Rcceivcd15 April 1986;a~g~te2~~ Ao~m I ~ ) Cochlear omer hah~lls aim bellied to play a ~ifl~i rote irt an lm~lffic.~t/oli proces~ whi~ ire-ally ~ - l h l ~ mit,r ~r sensiti~. ~ ! forward (~dca~-io--eMctrical) and revise f¢~l~s~trical-u~-~./¢atl lrasisthiclioa rely I~ im~v'¢d.. Wc hi~+~: prod~ d~lcas.= in laxhlem raier~phomcand ~ m ¢l~c~-y.evol~ .~hle, t ~ons ~sing tt~ drug. furo~n'dd¢~ data indicatc for~m'dand rc~-.c traasducti~ are llol a sim~¢ b i ~ o : ~ I~ and v.~g~ tllllI It~ o~t~ ha~].~dts~re pa~ a negative feedbacksystem. lt~i~:~ll; Tra~duction; CocMea: Futosemide hltr(Mmt~ A fount hypothesis in cochicar physiology is thai outer hair cells (OHC) act as ~omech~ni* cal ftmdba~ atnplitiers whi~ ar~ essential to nor- m~i auditory function {Davis, 1993; Neely and Kim. 1983; de Boer, 19113; Mmmtain ct at. 1983L The existence of the feedback ~ ~ not been wrifi~d, yet ~ system components ~ denamstmtea cxp~ingm~aUy. One d~r~m~_rau~ ~ompommt is forward tr~sduclion, the p ~ by which mechanically.indtuaM conductance changes in the haircdt apical membrane produc~ a receptor ~ t (P 1965}. The ~mi corn. Imaent, r~,~ traa +~don, h~ be~n dem~m- stratcd by injecting ac ~rl'~! into tl~ intact cocltltt and alcasating an layasti¢ rt~ponse at eardnim (Hubbard arm Mountain, 19tt3g This ri~pon~ may ix: dec to F'w,i~..~l lentlth c~'amS~ or st_~iary motion, both of wMch ha~ demonsiral~l in vitro using irti~cl~l CmTCnt U~A. (Browndl ¢t ~I.. 1~t5: Ashmor¢, 19117; Crliwfol~l a~d Fettipla~, 19g5). Fi~ I illgsiraies c~r negative feedback hy- poS. In respor,s. to a grand pressure at the eardrum, the hadlar membraile motion excites ialter h~r celts (IHCL soiding mformatitm to the brain via the auditory ~0 Witt~n lih¢ ¢~t1¢t4 bgsilar membrane ~on i~ aff~lgl by ti fi~d- b~,ck loop. for~ physii~ly by il~ OiiCs their alta~mealts. OHCs contain iwo scpat~ai¢ ~ : fol~,artt ih'KI i~verse transd,~ion, lf~ r e c t o r c~n-r+.~t prod~.~cd by f o r ~ Iransduc- results ill an ¢xlraceUuhl llial, ih¢ ~ r m/cr~hoitic (CM) (Dallos ¢md Che~th- am., 1976: ~tos ¢t aL, 1982: R•ssdt ¢1 ~o., l~g l~jected curtal pco~s an cx~ il?L4~Jl i 0 OHC reverse trm~sd~,c~, wh/ch produces a mc~V.ani~ disturbance inside the cochka. The dha~ remits ia ~¢ctricatVy-evogcd acoasti© cntissi~ms (E~E)+ w h i ~ cat~ be tn~..ammgi m M ~ (so,am pen~taL 75 mg/kg) a~d a~0rdintl to an itmitmio~j ~ro~ ~