Immunoreactions found in lamina I of the spinal dorsal horn in control rats showing multiple labellings at the level of the same neurite. Two immunoreactive zones (arrowheads) are present between an axon (A1) and a dendrite (D), and at the interface between two axons (A1 and A2). In both cases, no synaptic differentiation was noted. Labelling is strictly localized to the extracellular space between the two neurites. Scale bars = 500 nm.