On SIF cell-neuron relationships in autonomic ganglion.
Seldom found SIF cell processes in the lower mesenteric ganglion of the cat, in close proximity to principal ganglionic neurons either their axons or dendrites are described. Contacts between SIF cells and neurons could not always be regarded as unambiguous synapses. But the close proximity of both cells wrapped in the same satellite cells and same basal lamina, suggests the possibility of such synapses. Formations of narrow branches from main SIF cell processes were found in serial sections. In addition, these processes sometimes lost their Schwann cell envelope not only in the vicinity of blood capillaries, but also in the vicinity of the neuron. Some functional similarity between individual SIF cell groups in autonomic ganglia has been supposed. The hypothesis of adrenergic afferent and efferent synapse on SIF cell as a part of an inhibitory feedback loop between a SIF cell group and principal ganglionic neuron has been proposed. The endocrine function of SIF cells is considered to be a main role of these cells in autonomic ganglia.