Synaptic Functions of Invertebrate Varicosities: What Molecular Mechanisms Lie Beneath

Figure 1

Schematic representation of the three most common types of varicosities observed in invertebrate neuronal cultures (a). The bottom panels show confocal acquisitions of neurites belonging to the serotonergic Helix neuron C1 cocultured with its physiological target B2 and immunostained with anti-serotonin (red) and anti-synapsin (green) antibodies. In these sample images it is possible to identify a varicosity without a postsynaptic target in which neurotransmitter release can be detected using functional dyes or electrophysiological techniques (b); a presynaptic varicosity interconnected with its postsynaptic counterpart (c); a newly formed varicosity derived from an advancing growth cone in which well-defined synaptic vesicle pools have not yet organized (d). Scale bar: 10 μm.