The spatiotemporal characteristic of glycinergic inhibition in cochlear nucleus and vestibular nucleus by optical imaging

Objective To study the role of glycinergic inhibition in cochlear nucleus and vestibular nucleus. Methods Using multiple - site optical recording technique coupled with a voltage - sensitive dye (RH 155), the spatiotemporal activity was observed in both cochlear and vestibular nucleus in newborn mouse after electrical stimulation of the vestibu-locochlear nerve. Results In both CN and VN, the optical responses were enhanced obviously by the bath - applied strychnine (50 μM,STR), a glycine receptor antagonist. After application of STR, the amplitude of the spike and slow -signal (at the 10 ms point after the spike) in CN was increased to 154 ±34% (n = 23, elements), 271±91% (n =23, elements), respectively. On the contrary, the amplitude of the slow - signal in VN was increased to 149±56% (n = 17, elements). These amplitude values were significantly (P 0. 05) higher than the control ones. The amplitude of the spike in VN, however, was increased to 102 ± 14% . This increase was no significant (P 0. 05) . The excitatory enhancements were occurred in the central areas of the responses in CN and VN as well as in the edges areas of the responses. Conclusion Glycine is identified as an inhibitory neurotransmitter in cochlear nucleus (CN) and vestibular nucleus (VN) in newborn mice. Glycine primarily sharpens the lateral edges of the excitatory response area as well as modulates excitation within central portions of the excitatory response area of CN and VN.