Figure 4
From: Spinal neurons require Islet1 for subtype-specific differentiation of electrical excitability
Caudal primary motor neuron-like neurons have voltage-dependent outward current properties that resemble those of ventral lateral descending and Kolmer-Agduhr interneurons rather than caudal primary motor neurons. (A) In uninjected 24 hours post-fertilization (hpf) embryos, caudal primary motor neurons (CaPs), ventral lateral descending neurons (VeLDs), and Kolmer-Agduhr neurons (KA’s, KA”s) have detectable whole-cell inward current (INa/Ca). (B) CaPs of control morpholino (CtlMO) injected and uninjected embryos have INa/Ca of similar amplitude (A). CaP-like neurons of E3 morphants have INa/Ca amplitude that does not differ from control CaPs. (C) INa/Ca densities of ventral neurons are not significantly different except for VeLDs versus CaP-like cells (†P < 0.05, versus VeLD). (D) In control embryos, CaPs have larger amplitude whole-cell outward current (IKv/Ca) than do VeLDs, KA’s or KA”s. (E) CaPs of control morphants and uninjected embryos have similar IKv/Ca density. In contrast, CaP-like neurons, regardless of the presence or absence of a peripheral axon, have IKv/Ca amplitudes that are smaller than those of control CaPs and resemble those of ventral interneurons (D). (F) IKv/Ca densities are significantly smaller in VeLDs, KA’s and KA”s compared to control CaPs (*P < 0.001 versus CaP). IKv/Ca of CaP-like versus CaPs is significantly smaller (*P < 0.001 versus CaP), but does not differ from VeLDs, KA’s or KA”s. IKv/Ca densities do not differ significantly between ventral interneurons. (G) In uninjected embryos, CaPs have larger voltage-dependent potassium current (IKv) amplitudes than do ventral interneurons. Outward current properties of KA’ and KA” were not significantly different and are grouped as KA. (H) In control morphants (CaP CtlMO injected), CaP IKv resembles that recorded from CaPs in uninjected embryos (G). In E3 morphants, CaP-like IKv amplitude is reduced compared to that of control CaPs and more similar to that of ventral interneurons (see G). (I) CaPs have larger IKv densities versus interneurons (*P < 0.001 versus CaP). CaP-like neurons have IKv densities that are significantly reduced versus CaPs (*P < 0.001 versus CaP) but not interneurons.