Effects of parallel fiber stimulation on neurons of rat dorsal cochlear nucleus.
We have compared the effects of parallel fiber stimuli on extracellularly recorded neurons showing regular or bursting spontaneous activity patterns in the dorsal cochlear nucleus of rat brainstem slices. Ninety percent of regular neurons failed to respond to stimulus currents (1.4 +/- 0.28 mA, mean +/- SEM) significantly greater than those (0.4 +/- 0.07 mA) that elicited responses from 96% of bursting neurons. Responses of bursting neurons were elicited from widely separated loci along the molecular layer. Kynurenic acid and CNQX or DNQX blocked both spontaneous firing and responses to parallel fiber stimuli of bursting neurons. The same agents also blocked responses of regular neurons but had little or no effect on their spontaneous firing rates. AP-5 caused small decreases in spontaneous rates of both bursting and regular neurons but did not appear to affect responses to stimuli. The data support the hypothesis that the responses of both regular and bursting neurons to parallel fiber stimulation are mediated by glutamate, acting mainly through non-NMDA receptors. Spontaneous activity of bursting, but not regular, neurons also requires non-NMDA glutamatergic transmission, suggesting that the spontaneous firing of bursting neurons, consisting largely of cartwheel cells, may depend upon granule cell activity.
Waller
H J
HJ
Department Neurological Surgery, Medical College of Ohio, Toledo 43699, USA. hwaller@gemini.mco.edu
Godfrey
D A
DA
Chen
K
K
D015763:2-Amino-5-phosphonovalerate / Q000633:toxicity; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000633:toxicity; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D003051:Cochlea / Q000187:drug effects / Q000294:innervation*; D017626:Cochlear Nucleus / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000633:toxicity; D005260:Female; D007736:Kynurenic Acid / Q000633:toxicity; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D011810:Quinoxalines / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; C056723:FG 9041; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid