(A) Structure of the ChR2(ET/TC)-containing and opsin-free constructs. (B) Schematic drawing illustrating the orientation of electrode paddles for specific targeting of either (i) dHP or (ii) i/vHP pyramidal neurons. (C) Bar diagram displaying the mean number of embryos, electroporated embryos, surviving pups, and positively transfected pups when ChR2(ET/TC)-containing and opsin-free constructs for (i) dHP (n = 8 litters for opsin-containing group, n = 5 for opsin-free group) and (ii) i/vHP (n = 8 litters for opsin-containing group, n = 3 litters for opsin-free group). (D) Line plots displaying the developmental profile of somatic growth [body length, tail length, weight] and reflexes [vibrissa placing, cliff aversion and surface righting reflexes] of P2-8 pups expressing ChR2(ET/TC) or opsin-free constructs in (i) dHP (n = 17 for opsin-containing pups, n = 14 for opsin-free pups) and (ii) i/vHP (n = 9 for opsin-containing pups, n = 5 for opsin-free pups). Error bars represent SEM.