title: Spinal NMDA receptor involvement in expansion of dorsal horn neuronal receptive field area produced by intracutaneous histamine.
abstract: Histamine elicits the sensation of itch at the site of skin application as well as alloknesis (itch elicited by innocuous mechanical stimuli) in a surrounding area in humans and expansion of the low-threshold mechanosensitive receptive field area of spinal wide dynamic range (WDR)-type dorsal horn neurons in rats. We presently tested if the histamine-evoked expansion of neuronal receptive field area depends on a spinal N-methyl-D-aspartate (NMDA) receptor-mediated process. In pentobarbital sodium-anesthetized rats, mechanical receptive field areas of single WDR-type dorsal horn neurons were mapped with graded von Frey filaments before and 10 min after intracutaneous (ic) microinjection of histamine (1 microl; 1, 3, or 10%) at a low-threshold site within the receptive field. Intracutaneous microinjection of histamine evoked dose-related increases in firing rate, as well as a dose-dependent expansion in mean receptive field area 10 min after 3 and 10%, but not 1%, histamine doses. When a noncompetitive or competitive NMDA receptor antagonist dizocilpine [MK-801; D(-)-2-amino-5-phosphonovalerate (APV), respectively; 1 microM] was first applied topically to the surface of the spinal cord, there was no significant change in mean receptive field area after ic microinjection of 10% histamine. The mean neuronal response to histamine in the presence of spinal MK-801 or APV was not significantly different from the mean response to histamine in the absence of these drugs. These results suggest that spinal NMDA receptors are involved in histamine-induced expansion of mechanical receptive field area, a neural event possibly involved in the development of alloknesis.
authors.affiliation: Section of Neurobiology, Physiology and Behavior University of California, Davis, California 95616, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Jinks
authors.forename: E
authors.initials: E
authors.lastname: Carstens
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology*; D007271:Injections, Intradermal; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000187:drug effects*; D011984:Sensory Receptor Cells / Q000187:drug effects*; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D006632:Histamine