Selective retrograde transport of nipecotic acid, a GABA analog, labels a subpopulation of gerbil olivocochlear neurons.
Perfusion of the gerbil cochlea with micromolar quantities of 3H-gamma-aminobutyric acid (GABA) results in rapid, selective labeling of 50-60% of the olivocochlear (OC) efferent terminals on afferent dendrites beneath the inner hair cells, and all of the efferent terminals beneath the outer hair cells. In order to identify the neurons from which these GABA-accumulating terminals originate, the cell bodies were localized by using retrograde transport of 3H-nipecotic acid, a metabolically inert GABA analog. With survival times of 6-30 hours after cochlear injection, myelinated OC efferent fibers and cell bodies were well labeled, with the greatest number being labeled at 12-18 hours. All of the labeled neurons belonged to the medial OC system, and no lateral OC neurons were labeled. It is concluded that the GABA-accumulating endings in the gerbil cochlea arise from medial OC neurons, and therefore that medial OC efferent neurons in this species project to both inner and outer hair cell regions.
Ryan
A F
AF
Department of Surgery/Otolaryngology, UCSD School of Medicine 92093-0666.
Schwartz
I R
IR
Keithley
E M
EM
Wang
Z X
ZX
D000818:Animals; D001345:Autoradiography; D001692:Biological Transport / Q000502:physiology; D003051:Cochlea / Q000378:metabolism*; D005849:Gerbillinae / Q000378:metabolism*; D006735:Horseradish Peroxidase; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000502:physiology; D009476:Neurons, Efferent / Q000378:metabolism*; D009557:Nipecotic Acids / Q000493:pharmacokinetics*; D009847:Olivary Nucleus / Q000378:metabolism*; D010477:Perfusion; D011392:Proline / Q000031:analogs & derivatives*; D012680:Sensitivity and Specificity; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives*
D009557:Nipecotic Acids; D014316:Tritium; C030278:nipecotic acid; D005680:gamma-Aminobutyric Acid; D011392:Proline; C010983:homoproline; D006735:Horseradish Peroxidase