Dissociation between distortion-product and click-evoked otoacoustic emissions in sheep (Ovis aries).
Distortion-product otoacoustic emissions (DPOAEs) were weak or absent in about one-third of sheep (Ovis aries) of both sexes tested for otoacoustic emissions (OAEs) even though their click-evoked OAEs (CEOAEs) seemingly were typical of other sheep of the same sex. Various pieces of evidence suggest that the absence of measurable DPOAEs was unlikely to be attributable to anesthetic effects, a poorly located probe tip, a pressure differential between middle and outer ears, season of the year, body position during testing, temperature effects, or previous medical history. Sheep apparently can exhibit a marked dissociation between DPOAEs and CEOAEs. In those sheep having measurable DPOAEs, the DPOAEs were stronger in males than in females, which is the opposite direction of effect from the CEOAEs measured in these same sheep and in humans. In female sheep exposed to higher-than-normal levels of androgens during gestation, the measurable DPOAEs were stronger than in untreated females. Although this also was the opposite direction of effect from expected, it still was a shift in the male direction, in accord with past findings about the masculinizing effects of androgens on OAEs. In sheep, androgen exposure appears to have different effects on the mechanisms underlying DPOAEs from those underlying CEOAEs.
McFadden
Dennis
D
Department of Psychology and Center for Perceptual Systems, University of Texas, Austin, Texas 78712-0187, USA. mcfadden@psy.utexas.edu
Pasanen
Edward G
EG
Valero
Michelle D
MD
Roberts
Eila K
EK
Lee
Theresa M
TM
D000161:Acoustic Stimulation; D000728:Androgens / Q000494:pharmacology; D000818:Animals; D013196:Dihydrotestosterone / Q000494:pharmacology; D004424:Ear Canal / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D008297:Male; D009919:Orchiectomy; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects; D010052:Ovariectomy; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012737:Sex Factors; D012756:Sheep; D013739:Testosterone / Q000494:pharmacology
D000728:Androgens; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol