Publisher Summary This chapter discusses visceral receptors, chemoreceptors, and molecular aspects of receptor function. The chapter discusses two main topics: These are the structure and responses of possible electroreceptors in the platypus bill and the role of putative chemical transmitters in the initiation and modulation of sensory activity at certain sensory receptors such as cutaneous receptors, arterial chemoreceptors and visceral receptors. The use of immunohistological techniques, while providing a plethora of new data, seems to have raised far more new questions than provided answers to old ones. On the other hand, studying the direct effect of candidate transmitters on the responses of sensory receptors (an approach that has been used for about 50 years) still seems to yield less equivocal conclusions. In conclusion one got the impression from the proceedings of this and other sessions of the symposium that although some sensory physiologists are looking for neurotransmitters or modulators at sensory receptors; they seem to have had little or no luck so far!