[The effect of the joint stimulation of the central grey substance and substantia nigra on the low- and high-threshold startle reflexes in anesthetized rats].

Influences of separate and combined stimulation of the periaqueductal grey matter (PAG) and the substantia nigra (SN) on startle reflexes were studied in chloralose-anesthetized rats; the reflexes were low-threshold, tactile ones and high-threshold, spino-bulbo-spinal (SBS) ones. A clear interaction between effects of the PAG and SN stimuli occurred by combination of these stimulations was found. The interactions were exhibited with potentiation or diminution of influences evoked by separate stimuli depending on type of reflexes investigated and sorts of influences as well as on sequences of stimulations. Potentiation of the inhibitory action of PAG stimulation on the SBS-reflex by combination of PAG-SN was observed more often.