PAIRED-PULSE AND FREQUENCY POTENTIATION OF CORTICAL RESPONSES IN DEVELOPING RATS

The postnatal development of paired-pulse and frequency potentiations of the first positive and negative components (P1N1) of the cortical i nterhemispheric response (IHR) was studied in urethane anesthetized ra ts aged from 7 to 90 days. The paired-pulse potentiation appeared in t he rat sensorimotor cortex starting from the age of 15 days. The magni tude of potentiation increased with age. The interpulse interval induc ing maximum potentiation shortened from 125 ms in 15-day-old rats to 7 0 ms in adult rats. Similar results concerning the paired-pulse respon ses were found for visual cortex but the maturation was somewhat delay ed-potentiation first appeared at postnatal day (PND) 18. The frequenc y potentiation reached adult properties in the sensorimotor cortex by PND 25. There is no time coincidence in the development of the two pot entiation phenomena studied, paired pulse potentiation appeared earlie r than frequency potentiation.