What is the laminar organization of the dorsal horn of the spinal cord? The dorsal horn of the spinal cord can be divided into distinct laminae based on cytoarchitectural grounds, using traditional cell (Nissl) stains. This anatomic organization is paralleled by a physiologic laminar organization. Neurons in laminae I and II, the substantia gelatinosa, respond …
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What are the clinical and investigational roles of capsaicin? Capsaicin, the algogenic substance in hot peppers, selectively stimulates primary afferent C fibers. These C fibers express TRV1, capsaicin receptors that nonselectively gate cations, including sodium and calcium, which depolarize axons. Selective antagonists to capsaicin have been developed. These may reduce the contribution of this channel …
Major neurotransmitters involved in antinociceptive functions Dorsal horn nociception can be regulated by both local inhibitory interneurons and descending inhibitory pathways that arise in the brainstem. The majority of inhibitory interneurons use the neurotransmitters, gamma-aminobutyric acid (GABA) or glycine. These neurotransmitters inhibit the firing of dorsal horn nociceptive neurons by both presynaptic and postsynaptic controls. …
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Major neurotransmitters involved in nociception Primary afferent nociceptors contain a variety of neurotransmitters, including the excitatory amino acid glutamate and a variety of neuropeptides, such as substance P and CGRP. Glutamate acts upon several subtypes of receptors, including AMPA receptors that mediate a rapid depolarization of dorsal horn neurons, via influx of sodium and efflux …
Major ascending pathways that transmit nociceptive information The three major pathways of nociceptive information are the spinothalamic, spinoparabrachial and spinoreticular tracts. The cell origin of the spinothalamic tract is in the dorsal horn and intermediate gray matter of the spinal cord. Axons of these neurons cross to the anterolateral quadrant and ascend to the thalamus, …
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What is a wide dynamic range neuron? Wide dynamic range refers to neurons in the spinal cord that respond to a broad range of intensity of stimulation. For example, there are neurons in lamina V that respond to non-noxious brushing of the cell’s receptive field, as well as to intense mechanical stimulation and to noxious heat. …
What is meant by a second order neuron? Second order refers to all of the spinal cord neurons that receive input from the primary afferent fibers, including interneurons and projection neurons. Second-order neurons are also located in the dorsal column nuclei; these receive input from large, non-nociceptive, primary afferent fibers that ascend to the medulla via …