Figure 11.

Unaltered maturation of embryonically born cells grafted into the postnatal cortex. A, D, Experimental design. A, A retroviral vector expressing RFP was injected in utero in the brain ventricles of 5HT₃-EGFP embryos at E14.5. D, Newborn 5HT₃-EGFP neuroblasts were dissected from the caudal ganglionic eminence of 5HT₃-EGFP embryos at E14.5 and rapidly grafted into the postnatal cortex (layer VI) of P4 wt pups. B, E, Morphological reconstructions (axons in red, dendrites in black) illustrating that the two types of 5HT₃-EGFP interneurons born embryonically (multipolar and bipolar/bitufted) are similar in the two experimental conditions. Normal development in situ (B) or after grafting embryonic neuroblasts into the postnatal brain (E). C, F, Current-clamp recordings (left traces) and voltage-clamp recordings (right traces, V_hold = −60 mV) illustrate similar maturation of firing pattern and spontaneous activity, respectively, during the course of development in the two experimental conditions (C, born at E14.5; F, E14.5 grafted at P4). G, H, Electrophysiological properties of embryonically born neurons developing in situ and embryonically born neurons grafted ectopically at P4 as a function of neuronal age. Passive and active cell properties (G) and synaptic properties (H) are presented as mean ± SEM, at different time points after in utero virus injection (black dots) or graft of embryonically generated newborn cells (red dots). The number of neurons examined for each age category is between 6 and 18 except for AP half-width and AP frequency age 14–16 (3 nongrafted), τ_IPSC age 5–7 (5 grafted, 5 nongrafted) and τ_EPSC age 8–10 (5 grafted, 3 nongrafted). AP, Action potential.