Figure 6.

Differences in membrane properties are more evident in mature animals. (A) MSO neurons in the dorsal and in the ventral part of the MSO fire a single spike at the onset of depolarizing current injections and exhibit a voltage sag during hyperpolarizing current steps. In particular, in ventral neurons the voltage sag only is obvious for strong hyperpolarizing current injections due to the large resting conductance of I_h. (B) Peak input resistance and (C) membrane time constant vary significantly between ventral (n = 10) and dorsal (n = 12) neurons. Differences in the input resistance and in the membrane time constant between ventral and dorsal neurons are significantly larger in P22 animals compared with P18 animals. (D) IPSP time course changes along the dorsoventral axis as depicted in the inset. The half-width of IPSPs is largest in dorsal neurons and the time course accelerates during stimulation with IPSC trains. (E) The mean values for the rise time (10–90%) of the first IPSP (dark-gray bars) and the decay time (90–10%) of the last IPSP (light-gray bars) are larger in dorsal neurons compared to ventral neurons. (F) IPSP time course is accelerated in P22 compared to P18. Representative normalized IPSP trains for the ventral part of the MSO. (G) Half-widths for the first IPSPs are decreased for P22 in both the ventral and the dorsal part of the MSO. Black symbols: dorsal neurons; white symbols: ventral neurons. ^*P < 0.05, ^**P < 0.01, two-tailed unpaired t-test.