title: Substance P differentially modulates firing rate of solitary complex (SC) neurons from control and chronic hypoxia-adapted adult rats.
abstract: NK1 receptors, which bind substance P, are present in the majority of brainstem regions that contain CO2/H(+)-sensitive neurons that play a role in central chemosensitivity. However, the effect of substance P on the chemosensitive response of neurons from these regions has not been studied. Hypoxia increases substance P release from peripheral afferents that terminate in the caudal nucleus tractus solitarius (NTS). Here we studied the effect of substance P on the chemosensitive responses of solitary complex (SC: NTS and dorsal motor nucleus) neurons from control and chronic hypoxia-adapted (CHx) adult rats. We simultaneously measured intracellular pH and electrical responses to hypercapnic acidosis in SC neurons from control and CHx adult rats using the blind whole cell patch clamp technique and fluorescence imaging microscopy. Substance P significantly increased the basal firing rate in SC neurons from control and CHx rats, although the increase was smaller in CHx rats. However, substance P did not affect the chemosensitive response of SC neurons from either group of rats. In conclusion, we found that substance P plays a role in modulating the basal firing rate of SC neurons but the magnitude of the effect is smaller for SC neurons from CHx adult rats, implying that NK1 receptors may be down regulated in CHx adult rats. Substance P does not appear to play a role in modulating the firing rate response to hypercapnic acidosis of SC neurons from either control or CHx adult rats.
authors: Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, United States of America.
authors: Nicole L
authors: NL
authors: Nichols
authors: Division of Physiology, University of California San Diego School of Medicine, La Jolla, California, United States of America.
authors: Frank L
authors: FL
authors: Powell
authors: Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, Florida, United States of America.
authors: Jay B
authors: JB
authors: Dean
authors: Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio, United States of America.
authors: Robert W
authors: RW
authors: Putnam
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D017552:Solitary Nucleus / Q000187:drug effects* / Q000502:physiology; D013373:Substance P / Q000494:pharmacology*
chemical_list: D018040:Receptors, Neurokinin-1; D013373:Substance P