The Pattern and Place of Nociceptive Modulation in the Dorsal Horn
Recent technical innovations have advanced the study of the mechanisms of pain and analgesia. These advances have resulted in an increased understanding of the anatomical organization of the dorsal horn at the medullary and spinal levels. Studies employing immunocytochemical labeling of neurotransmitters, retrograde transport of HRP, and intracellular HRP techniques have been at the forefront. The greatest strides, however, have been made when two of these approaches were combined in a single experiment to identify relationships between two labeled elements simultaneously. Many of the multiple-label experiments that were first accomplished in the dorsal horn are applicable throughout the nervous system. The observations are useful from the perspective of basic concepts of neural circuitry as well as a characterization of the pathways involved in pain and analgesia. Study of the spinal cord dorsal horn offers a unique advantage in that it contains many of the identified substances in the nervous system that act as neurotransmitters or neuromodulators (Table I). These neurochemicals include both classical neurotransmitters such as the monoamines and amino acids as well as recently discovered families of neuropeptides. This chapter seeks to address some of the fundamental observations on the anatomical and neurochemical organization of the dorsal horn and to apply the findings to basic issues of integration in the nervous system as well as to the study of pain and analgesia.
KeywordsDorsal Horn Projection Neuron Dorsal Horn Neuron Superficial Dorsal Horn Substantia Gelatinosa
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