Dynorphin release by the lateral olivocochlear efferents may inhibit auditory nerve activity: a cochlear drug delivery study.
Dynorphin (dyn) is suggested to excite the auditory nerve (AN) when released by the lateral olivocochlear (LOC) efferents. However, previous studies evaluated either intravenously delivered dyn-like agents, raising the potential for systemic (central) effects, or agent concentrations unlikely to be achieved via endogenous cochlear release. This study tested the hypothesis that biologically relevant increases in dyn levels in the cochlea achieved via diffusion of the drug of (-)pentazocine across the round window membrane enhances AN firing. In general, amplitude of the cochlear whole-nerve action potential (CAP) was depressed following drug application. These results suggest that dyn released by the LOC neurons would likely act as an inhibitory transmitter substance in the LOC system; neurotransmission is one of the LOC system's vast unknowns.
Department of Otolaryngology, University of Michigan, USA. Electronic address: colleeng@ufl.edu.
Colleen G
CG
Le Prell
Department of Surgery, Southern Illinois University School of Medicine, USA.
Larry F
LF
Hughes
Department of Otolaryngology, University of Michigan, USA.
Sanford C
SC
Bledsoe
D000161:Acoustic Stimulation; D000200:Action Potentials; D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism; D001309:Auditory Threshold; D003051:Cochlea / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D003056:Cochlear Nerve / Q000187:drug effects* / Q000502:physiology; D004399:Dynorphins / Q000378:metabolism*; D004525:Efferent Pathways / Q000378:metabolism; D005072:Evoked Potentials, Auditory; D005260:Female; D006168:Guinea Pigs; D008297:Male; D010423:Pentazocine / Q000494:pharmacology*; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D065832:Superior Olivary Complex / Q000502:physiology*
D017473:Receptors, Opioid, kappa; D004399:Dynorphins; D010423:Pentazocine
Auditory nerve; Cochlear whole nerve action potential; Dynorphin; Kappa opioid receptor; Lateral olivocochlear efferent