Neuronal transmission mechanisms

Several techniques were used to study the morphology of the salivary apparatus of the cockroach, Nauphoeta cinevea. A general survey of the ultrastructure was made. The acinar cells were of two distinct types: peripheral and central cells. The ducts that these cells give rise to could be classified into three morphologically distinct areas. The fine structure of the reservoir ducts was also studied.Intracellular injections of Procion yellow dye and the use of lanthanum, as an electron dense marker, showed that there were many intercalated gap-junctions between the septate desmosomes of the acinar cells.The innervation of the apparatus was studied in detail and it was observed, using techniques of fluorescence histochemistry and electron microscopy, that the salivary nerves, which arise from the suboesophageal ganglion, branch over the surface of the acini. The axons associated with the acini were found to be of two morphologically distinct types, designated type A and type B. Several histochemical tests indicated that type A axons contained a catecholamine.It was attempted to stimulate the salivary nerves. This resulted in structural changes within peripheral cells and type A axons. When the salivary nerves were cut several degenerating axon profiles could be identified in association with the gland cells. This was not observed when the stomatogastric nerve was cut.Finally, enzyme-inhibiting drugs were used to interrupt the synthetic pathways of catecholamines. These experiments led to a number of unexpected results including the observation that some of the actions of these drugs appeared to be postsynaptic