Functional asymmetry of the auditory centers in the guinea pig

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1 Auditory system S T A I N I N G OF C O C H L E A R ANTISERUM

H A I R CELLS

BY T R I P H O S P H O I N O S I T I D E

(TPI)

T E T S U R O H O R I K O S H I * , KEIJI Y A N A G I S A W A and TOHRU Y O S H I O K A D e p a r t m e n t of P h y s i o l o g y , T s u r u m i U n i v e r s i t y , 2-1-3 Tsurumi, T s u r u m i - k u Y o k o h a m a 230 and D e p a r t m e n t of Physiology, Y o k o h a m a City U n i v e r s i t y , M i n a m i - k u Y o k o h a m a 232, Japan. A m i n o g l y c o s i d e s are k n o w n to be ototoxic, and they c o m p e t e w i t h Ca 2+ w h i c h a c t i v a t e s t r a n s d u e t i o n of hair cells. As a c a n d i d a t e for b e i n g an a m i n o g l y c o s i d e s receptor, TPI has been proposed. R a b b i t s w e r e i m m u n i z e d w i t h T P I - h a p t e n s u s p e n s i o n s by i n t r a v e n o u s injection. B i n d i n g a c t i v i t y of this a n t i s e r u m to v a r i o u s p h o s p h o l i p i d s showed that the a n t i s e r u m s p e c i f i c a l l y reacts w i t h TPI. S t e r e o c i l i a of b o t h inner and o u t e r hair cells of the guinea pig c o c h l e a were stained c l e a r l y by the PAP method, using the a n t i s e r u m to TPI as a p r i m a r y antiserum. The cell b o d i e s of hair cells and s u p p o r t i n g cells Were not stained. A f t e r the a n t i s e r u m was a b s o r b e d by i n c u b a t i o n w i t h excess TPI, the r e a c t i v i t y of TPI was r e d u c e d to about 30 % of its o r i g i n a l value in r a d i o i m m u n o a s s a y ; and the a n t i s e r u m stained the stereocilia weakly. The s t e r e o c i l i a of hair cells were stained by r u t h e n i u m red, but their s t a i n i n g i n t e n s i t y was the same as the cell b o d i e s of s e n s o r y and s u p p o r t i n g cells. The E L I S A test also showed that the a n t i s e r u m was specific to TPI. These results suggest that the a n t i s e r u m of the p r e s e n t study binds s p e c i f i c a l l y to TPI. C o n s i d e r i n g its high a f f i n i t y to Ca 2+ and a m i n o g l y c o s i d e s , TPI may be one of the m o l e c u l e s i n v o l v e d in the mechanical transduction. FUNCTIONAL ASYMMETRY OF THE AUDITORY CENTERS IN THE GUINEA PIG IKUO TANIGUCHI and HIDEKAZU TANAKA*, Dept. of Auditory Disorders, Medical Research Institute, Tokyo Medical and Dental University,

1-5-45 Yushima, Bunkyo-ku, Tokyo 113, Japan

Auditory evoked potentials of the unanesthetized guinea pig were topographically

analyzed.

Thirteen epidural electrodes were symme-

trically implanted on the biiateral hemispheres under pentobarbital anesthesia (Nembutal 30 mg/kg, i.p.).

Isopotential contour maps were

constructed under two different conditions of sound stimulation: click alone, and click against the background of species-specific vocalization sounds.

The maps obtained from 18 brains showed hemi-

spheric symmetry for stimulation with the click alone.

Fifteen of

the symmetrical brains, however, showed asymmetry when species-specific vocalization sounds were presented in addition to the click. Lateral specialization

of the central organization to process bio-

logically significant sounds, may exist even in nonverbal species.