Inferior colliculus in the rat: neuronal responses to stimulation of the auditory cortex.

Responses to electrical stimulation of the auditory cortex (silver ball bipolar electrodes, single pulses, duration 0.2 ms, current 0.1-1.5 mA) were recorded in neurones in the inferior colliculus of rats anaesthetized with pentobarbital. Excitatory or inhibitory effects were obtained in 84 out of 162 recorded neurones. The majority of neurones responded with a short excitatory burst (with a latency from 3 to 15 ms); in some of them the initial excitation was followed by inhibition lasting from 30 to 150 ms. Few neurones only reacted to electrical stimulation by inhibition, which occurred 3-10 ms after the stimulus and lasted up to 300 ms. The inhibition either suppressed the spontaneous activity or the acoustically evoked response. Neurones reacting to stimulation of the auditory cortex were found mainly in the caudal and dorsal parts of the inferior colliculus.