Decreased inhibition to lateral superior olive neurons in young and aged Sprague-Dawley rats.
Lateral superior olive (LSO) neurons in young and aged Sprague-Dawley rats have functional properties consistent with a limited contralateral inhibition, which is markedly different from other animals. An unusually low proportion of LSO cells (36/113) exhibited contralateral inhibition (and ipsilateral excitation, IE), while over 25% of LSO units exhibited excitatory responses to contralateral stimuli. Inhibition of most IE LSO neurons was evident only when the contralateral intensity was greater than the ipsilateral intensity, resulting in a marked shift in sensitivity to interaural intensity differences (IID). The firing rate of IE neurons was also affected more by a change in intensity of ipsilateral compared to contralateral stimuli. The shift in the IID sensitivity and the relative decrease in effectiveness of contralaterally driven inhibition in Sprague-Dawley rat LSO neurons could be due to decreased inhibitory inputs from the MNTB principal cells, increased contralateral excitatory effects and/or increased ipsilateral excitatory effects. Age-related decreases in the numbers of MNTB neurons observed anatomically is not reflected in a change in LSO function. The Sprague-Dawley rat may be a useful model for the effect of reduced inhibition in the superior olivary complex on auditory behavior.
Finlayson
P G
PG
Department of Surgery (Otolaryngology), University of British Columbia, Vancouver, Canada.
D000161:Acoustic Stimulation; D000375:Aging / Q000473:pathology / Q000502:physiology*; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects / Q000502:physiology*; D006319:Hearing Loss, Sensorineural / Q000473:pathology / Q000503:physiopathology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009847:Olivary Nucleus / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013223:Statistics as Topic
D000777:Anesthetics