434 



B 



'\/^^ 



Fig. 6. Effects of topically applied GABA on s.c.r.'s evoked in new-born cat. 



A. 5-hr-old kitten: (1) s.c.r.'s recorded 1-5 mm from stimulating electrodes; 

 (2) 20-30 sec after topical application of 1% GABA; (3) 10-20 sec after (2); 

 (4) early recovery phase after rinsing cortex with warm Ringer's solution. 



B. 1 5-hr-old kitten: (5) s.c.r.'s recorded 1-5 mm from site of stimulation; 

 strong stimulus evoked s.c.r.'s followed by prominent surface-positivity; 

 (6) 30 sec after 1 % GABA, unmasking of surface-positivity presumably re- 

 flecting sub-surface depolarizing p.s.p.'s; (7) recovery after removal of GABA. 



Cal. 100 c/s; 03 mV. 



following GABA-blockade of the s.c.r. and other responses evoked in mature 

 cortex has been noted previously (Purpura et a/., 1959b). The absence of a 

 prominent surface-positivity in the s.c.r. after ehmination of surface-nega- 

 tivity by GABA was characteristically observed in the neonatal period. There- 



FiG. 7. (l)-(6) 5-day-old kitten; (7)-(8) 5-week-old kitten. (1) Control s.c.r.'s 

 recorded 1-5 mm from stimulating electrodes; (2) 20 sec after topical applica- 

 tion of 1% GABA; (3) 30 sec after (2) and after application of additional 

 GABA ; (4) early recovery of s.c.r. after flushing cortex with warm Ringer's 

 solution; (5) late phase of recovery; (6) 20 sec after topical application of e-amino 

 caproic acid (Ce); (7) s.c.r.'s recorded at 2 mm; (8) 20 sec after topical 

 application of Ce. Cal. 100 c/s; 0- 1 mV. 



