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Figure 1 | Neural Development

Figure 1

From: Molecular components underlying nongenomic thyroid hormone signaling in embryonic zebrafish neurons

Figure 1

p38 and protein phosphatase 1 blockade altered tonic sodium current peak amplitudes. (A) INa was elicited by depolarizing voltage steps ranging between -70 and +70 mV in 125 mM extracellular sodium solution from a holding potential of -80 mV. Traces represent recordings obtained from a Rohon-Beard cell (RB) sensory neuron in a 50 hpf embryo. (B-D) To block relevant kinase pathways, we incubated the exposed zebrafish spinal cord preparation in the indicated inhibitors for 1 hour prior to recording INa peak amplitudes. We blocked two separate kinase pathways, ERK1/2 and p38, with the inhibitors PD98059 and SB203580, respectively. In order to block protein phosphatase (PP) activity, we used two different okadaic acid (OA) concentrations that inhibit either PP2A only (1 to 20 nM), or both PP2A and PP1 (1 μM). (B) After a 1 hour incubation in SB203580, RB INa peak amplitude increased. Conversely, 1 μM OA decreased RB INa peak amplitude. (C) Average current-voltage (I-V) relationships for INa recorded after p38 and PP1 inhibition showed changes in INa amplitude without alteration of the reversal potential (Erev). p38 inhibition (n = 14) led to an increase in INa amplitude compared to controls (n = 23). In contrast, phosphatase inhibition with 1 μM OA (n = 7) reduced INa compared to controls. Neither treatment affected Erev. (D) Peak INa amplitudes of cells exposed to the ERK1/2 inhibitor PD98059 (n = 16) did not significantly change INa peak amplitude compared to controls (n = 23). However, incubation of zebrafish embryos in the p38 inhibitor SB203580 (n = 14) significantly increased INa peak amplitude (P < 0.05; ANOVA). Inhibition of PP2A (1 and 20 nM OA; n = 6 and 11, respectively) did not significantly change peak INa amplitude compared to controls. However, 1 μM OA (n = 7), which inhibits both PP2A and PP1, resulted in a significant reduction in INa peak amplitude (P < 0.05; ANOVA). Asterisks represent a p-value of < 0.05 and error bars represent standard errors.

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