Effects of the substantia nigra (pars compacta) stimulation on two functional types of startle reflexes were studied in chloralose-anesthetized cats. The reflexes were the low-threshold ones evoked by tactile stimuli (T-reflex) and high-threshold ones evoked by intense peripheral nerve stimulation (spino-bulbo-spinal, SBS reflex). It was found that substantia nigra stimulation exerted mainly inhibitory influences on both types of reflexes. However the depression of the SBS-reflex was always more profound and long lasting (up to 8 min) than that of T-reflex. The latter reflex was sometimes facilitated.
Animals Cats