Fig. 14.     A: Topography of synaptic inputs to a typical cholinergic neuron in the SI. Compiled from our data as well as that of Bolam et al. (l986); Chang et al. (l987) and Martinez-Murillo et al., (l988a, 1990). Putative inhibitory synapses are labeled by solid, excitatory contacts by open symbols. B: Somatostatin-containing bouton in synaptic connection with the dendrite. Double labeling with nickel enhanced DAB/DAB. C: Bouton containing large neurosecretory granula (small arrows) establishing synaptic contact with the distal dendrite. Single immunostaining for ChAT. D: GABAergic bouton labeled with ferritin (small arrow) establishes symmetrical contact with the cholinergic cell body. From the material of Záborszky et al. (1986) by permission of Willey and Liss. E: ChAT-positive bouton contacts proximal ChAT-positive dendrite. Single immunostaining enhanced with cobalt. F: DBH-positive bouton establishes asymmetric synapse with a cholinergic dendrite. Double immunolabeling with NiDAB/ DAB. Arrowheads show subsynaptic dense bodies. In all micrographs large arrows point to the postsynaptic side of the synapse, asterisks label the immunostained (ChAT) profile. Bar scale for all micrographs: 1 µm.