Capsaicin-sensitive sensory nerve terminals with local and systemic efferent functions: Facts and scopes of an unorthodox neuroregulatory mechanism

The aim of this chapter is to briefly summarize the earlier and recent evidence, which suggest that polymodal nociceptors and other capsaicin-sensitive (CS) sensory receptors subserve an unorthodox dual sensory-effector function with important neuroregulatory relevance. Sensory receptors are nerve terminals, which are specialized by definition to receive stimuli from the inner or outer environment and convey this information to the central nervous system or some peripheral neural circuitry. A modem version of this orthodox uni-directional neuroregulatory arrangement is completed also by a bi-directional influence of chemical synapses in a self-modifiable way, emphasizing the importance of long-term retrograde signals, for example, in synaptic plasticity or in back diffusion of nitrogen monoxide signal molecules. In spite of all these considerations, including pre-synaptic modulation of neurotransmission at efferent autonomic nerve terminals, transmission of messages to the central nervous system could not be achieved through neuroeffectors, and in terms of neuroregulation, they do not have dual sensory-efferent function. © 1996 Elsevier Science B.V.