Frequency and intensity are two of the important parameters of sounds. Many researchers use spike rate of auditory neurons to represent the two parameters generally. Some studies showed that response latency may represent frequency and intensity too. However, it is not clear where the two parameters are encoded by response latency in the auditory pathway. GABA and glycine are two ubiquitous inhibitory neurotransmitters. Iontophoretically bicuculline (antagonist to GABA-A) or strychnine (antagonist to glycine) was injected to observe the change of response latency. If the relationship between response latency and intensity or frequency has changed, sound may be encoded locally. If the relationship keeps unchanged, this information may be transferred from the inferior nervous centres. The auditory neurons in the inferior colliculus and A1 area of auditory cortex of BALB/c mouse were studied. The results show that the relationship between response latency and intensity or frequency didn't change after the application of bicuculline or strychnine. It suggests that the encoding relationship between response latency and intensity or frequency didn't be completed in the inferior colliculus or A1 area of auditory cortex, but it is probably transferred from the inferior nervous centres.