Figure 5.

Inhibition of CaMKII prevents the effect of NT3. A peptide inhibitor for CaMKII (CaMKII-pep), together with rhodamine-dextran, was injected into Xenopus embryo at the two-cell stage, and the nerve–muscle co-cultures were prepared from the injected embryos. (A) Super-imposed phase and fluorescence micrographs of the 1-d-old nerve–muscle co-cultures showing cells loaded with (+) or without (−) CaMKII-pep. N, spinal neurons; M, myocytes. (B) A pair of recordings showing that loading of CaMKII peptide into presynaptic neurons N(+) prevented the NT3-induced increase in SSC frequency, whereas NT3 still enhanced transmitter release in a N(−) neuron in the same culture. (C) Summary of the effect of CaMKII-pep loaded into either presynaptic spinal neurons or postsynaptic myocytes. The number of synapses recorded are indicated above each pair of columns. In all N− conditions, application of NT3 elicited a significant increase in SSC frequency (P < 0.01, t test).