THE SURFACE EVOKED-POTENTIAL AND PARVALBUMIN-IMMUNOREACTIVITY IN THE SOMATOSENSORY CORTEX OF THE DEVELOPING RAT

The development of the rat somatosensory system was followed electroph ysiologically and immunohistochemically. In the surface evoked potenti al elicited in the primary somatosensory cortex by electrical stimulat ion of the whisker C3 follicle, a short-latency positive wave was firs t recorded on postnatal Day 2. A long-latency positive wave was record ed in some pups on postnatal Day 7 and in most pups on postnatal Day 8 . On postnatal Day 10, a PIN complex appeared between the short- and l ong-latency positive waves. Parvalbumin, believed to appear with funct ional maturation, appeared mainly after postnatal Day 7 in Layer V in the underlying area, although a few weakly stained cells appeared on p ostnatal Day 5. On postnatal Day 10, weakly stained cells appeared in the area containing barrels; their staining increased with time. In th is system, electrophysiological and immunohistochemical parameters cha nged by the 3rd postnatal week with the most marked changes occurring within 2 postnatal weeks. (C) 1995 John Wiley and Sons, Inc.