Networks of synaptically connected neurons underlie all brain functions. Various
cell-cell signaling and extrinsic molecules influence synapse assembly at the synaptic
site. Calcium ions play a significant role in signal transduction pathways that control
various neuronal functions. Multifunctional Ca2+/calmodulin-dependent protein
kinase II (CaMK II) is an important mediator of calcium signaling in neurons, it
plays an essential role in controlling synaptic strength and plasticity, and it is highly
expressed in the cytosol of developing neurons, especially in presynaptic neurons.
However, the precise role of CaMKII in synapse formation and synaptic
transmission has not yet been determined. We hypothesized that CaMKII activity
could be necessary for synapse formation and synaptic transmission. To test whether
CaMKII activity is required for the synapse formation and synaptic transmission,
the identified neurons visceral dorsal 4 (VD4 – presynaptic) and its postsynaptic
partner left pedal dorsal 1 (LPeD1) from the freshwater snail Lymnaea stagnalis
were paired in soma-soma configuration in cell culture. The soma-soma paired cells
recapitulated their excitatory connections in vitro. To test the possible role of
CaMKII in synapse formation and synaptic transmission, the in vitro paired
neurons were exposed to a CaMKII-specific inhibitor KN-93 and its inactive analog
KN-92. The incidence of synapse formation and efficacy of synaptic transmission
was tested electrophysiologically.