ANALYSIS OF SOME EVOKED SYNAPTIC ACTIVITIES 437 



distant s.c.r.'s and produced some augmentation in background activity, 

 whereas Cg produced much less depression of s.c.r.'s and initiated local 

 paroxysmal discharges (Fig. 10 (6)). 



Fig. 10. S.c.r.'s recorded at 1 -5 mm (upper channel) and 5 mm (lower channel) 

 from the site of stimulation. Left column, cal. 100 c/s; right column, cal. lOc/s. 

 (1) and (2) Control; (3) and (4) maximum action of Ce; (5) and (6) after complete 

 recovery from Ce action and 2 min after topical Cs. Records in (5) taken immed- 

 diately before development of seizure activity shown in (6). 



During the second postnatal week, further differences in the effects of Ce 

 and Cs were observed. As shown in Fig. 1 1, in records from 10 and 12 day- 

 old-kittens from the same litter, Ce produced depression of near and distant 

 s.c.r.'s. In the older kitten this depression was associated with sporadic 

 spontaneous paroxysmal activity. In contrast, Cg produced depression of the 

 early component in the near s.c.r., and augmentation of late components. Of 

 particular significance was the finding that during the initial stages of Cg 

 action on near responses, s.c.r.'s recorded 4-5 mm away from the site of 

 stimulation were depressed by the amino acid or relatively unaffected until 

 the onset of paroxysmal activity. 



Towards the end of the third postnatal week, the depressant effects of Ce 

 and Cg on near s.c.r.'s were no longer observed. Comparison of the different 

 effects of Ce and Cg on near s.c.r.'s evoked in an 8 day-old-animal, and of 

 Ce on near and 4 mm distant responses in a 3 week-old-litter-mate is shown 

 in Fig. 12. Two features are especially noteworthy. In the 8 day-old-animal, 

 Ce depressed all components of the s.c.r. (Fig. 12 (3)), whereas Cg depressed 

 early and augmented late components and induced convulsant activity (Fig. 

 12 (5), (6)). In the 21 day-old-litter-mate, Ce rapidly augmented all compo- 

 nents of the near s.c.r., but did not significantly alter distant responses 

 (Fig. 12 (9)). Augmentation of the second, late negativity in near s.c.r.'s 

 was more prominent than the increase in the early negativity. The onset of 

 paroxysmal discharges after Ce resulted in marked fluctuations in late 



