Dorsal raphe nucleus modulates sensory evoked responses in caudate and septum

The dorsal raphe nucleus (DR) was examined for its possible modulatory effects on sensory input to the caudate nucleus (CN) and lateral septum (Spt) in freely behaving rats. Three types of DR stimulation were tested for their effects on sensory evoked responses: (1) a single pulse of electrical stimulation of the DR prior to each sensory stimulus, (2) a 5-20 min burst of 20 Hz stimulation of the DR prior to sensory stimulation, and (3) a combination of the single pulse and the 5-20 min burst (20 Hz) stimulation of the DR prior to the sensory stimulation. Each of the three forms of DR stimulation caused a decrease in the amplitudes of the sensory-evoked responses recorded from the CN and Spt. Combination of DR stimulation caused stronger (summation) attenuation of the sensory responses. Thus, DR was shown to affect sensory input recorded in CN and Spt.