EFFECTS OF POSTNATAL BLOCKADE OF CORTICAL ACTIVITY WITH TETRODOTOXIN UPON THE DEVELOPMENT AND PLASTICITY OF VIBRISSA-RELATED PATTERNS IN THE SOMATOSENSORY CORTEX OF HAMSTERS

Several previous studies have shown that postnatal blockade of thalamo cortical activity with either tetrodotoxin (TTX) or the N-methyl-D-asp artate (NMDA) receptor antagonist D,L-2-amino-5-phosphonovalerate (APV ) does not prevent the formation of vibrissa-related patterns in the p rimary somatosensory cortex of rats. One limitation of these studies i s that this pattern forms very shortly after birth in rats, and there may be only a very limited time over which it may be influenced by act ivity blockade. In the present study, the effect of activity blockade was evaluated in a more altricial rodent, the hamster. The present stu dy showed that a pattern of thalamocortical afferents corresponding to the vibrissae is not observed until the fourth postnatal day in hamst ers. Nevertheless, application of TTX-impregnated implants to the cort ices of newborn hamsters had no qualitative or quantitative effect upo n vibrissa-related patterns in the primary somatosensory cortices of t hese animals. Moreover, TTX implants did not prevent the changes in pa tterns that followed cauterization of a row of vibrissa follicles.