Table 1.

Electrophysiological features of FS cells, during the first two postnatal months

Age (week)	Vrest (mV)	Spike width (ms)	4th spike interval/1st spike interval	AHP (mV)	N
3rd	−69.3 ± 0.45	0.70 ± 0.06	1.36 ± 0.06	−13.6 ± 1.6	13
4th	−70.1 ± 0.25	0.71 ± 0.05	1.27 ± 0.05	−14.5 ± 0.9	28
5th	−69.6 ± 1.26	0.90 ± 0.16	1.33 ± 0.09	−13.7 ± 3.2	5
7th–9th	−70.0 ± 0.65	0.75 ± 0.16	1.13 ± 0.04	−11.7 ± 0.7	23

Firing parameters at the indicated postnatal weeks. For comparison, the ratios between the fourth and the first spike interval in a sample of pyramidal cells from the same mice were 2.3 ± 0.48 (<P28; n = 9), and 2.6 ± 0.39 (>P28; n = 14), at firing frequencies of 10–50 Hz. All differences between age groups were NS. In a representative sample of FS cells (n = 8, from six mice) R_in was 82.2 ± 7 MΩ in the first month, and 55.6 ± 4.5 MΩ after P45 (n = 17, in eight mice). For comparison, R_in for regular-spiking non-pyramidal cells was 98.8 ± 12 MΩ (n = 5, from five mice in the first month of life).