Effects of Peripheral Stimulations on the Paired-pulse Facilitation in the Anterior Cingulate Cortex Following the Stimulation in the Medial Thalamus

In our previous study, paired-pulse facilitation (PPF) was found in rat’s anterior cingulate cortex (ACC) following the stimulation of the medial thalamus (MT). The present study examines the effect of various peripheral stimulations on the PPF in both consciously awake and anaesthetized rats. During the chronic test, effects of different peripheral stimulations on PPF were measured in consciously awaken, and freely moving rats. During acute test, effects of sciatic nerve electrical stimulation on the PPF was investigated in anesthetized (Pentothal, 6.25mg/100g) rats. The results showed that the PPF measured in the ACC was affected by the applications all types of peripheral stimulations. With the applications of noise, brushing and pinching stimuli, this PPF had been decreased to 58.04±11.96%, 58.22±8.21% and 51.15±6.63% respectively while compared to the control rats. In the formalin injection test, the PPF decreased to 79.66±4.99% in phase 1 (after 1-5 mines) and 81.40±8.21% in phase 2 (after 18-30mins). In the laser stimulation test, the PPF was decreased to 64.66±14.72% when the laser stimulation preceded paired-pulse stimulation with 100-200ms and 60.05±14.83% when the delay was 350-500ms. In the state of fear conditioning and non-movement, PPF increased to 112.52±3.14% and 123.55 ±2.76%. Two way ANOVA showed that PPF was decreased when rat was placed in a rotated box with faster rpm (F=45.04 P<0.001). However, there was no statistically significant difference between 150