title: 5-HT1A receptors mediate the effect of the bulbospinal serotonin system on spinal dorsal horn nociceptive neurons.
abstract: The present study examined whether the effect of stimulation of the nucleus raphe magnus (NRM) is mediated by spinal cord dorsal horn serotonin1A (5-HT1A) receptors in the rat. This hypothesis predicts that nociceptive dorsal horn units inhibited by NRM stimulation or iontophoretic 5-HT application would also be inhibited by iontophoresis of the selective 5-HT1A agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and buspirone. A total of 78 dorsal horn wide-dynamic-range neurons were recorded. Overall, 62% of the cells tested (48/78) were responsive to electrical stimulation of the NRM with the predominant response being inhibitory (38/48; 79%). Fifty-eight cells were tested for their response to both NRM stimulation and 8-OH-DPAT iontophoresis: 20/58 cells were inhibited by NRM stimulation and 50% of the cells inhibited by NRM stimulation were also inhibited by 8-OH-DPAT. Fifty-two cells were tested for their response to both NRM stimulation and buspirone iontophoresis: 14/52 cells were inhibited by NRM stimulation with 9/14 similarly inhibited by buspirone. To examine whether exogenously applied serotonin produced an effect through 5-HT1A receptors, the effect of both 5-HT and 8-OH-DPAT iontophoresis was tested on 57 dorsal horn neurons. The majority of cells (25/57) were inhibited by 5-HT application; 15/25 were similarly inhibited by 8-OH-DPAT. The response of 48 dorsal horn cells to 5-HT and buspirone iontophoresis was compared. Forty-four percent (21/48) of the cells were inhibited by 5-HT; 16/21 were also inhibited by buspirone.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Psychiatry, University of Cincinnati College of Medicine, Ohio 45267-0559.
authors.forename: F P
authors.initials: FP
authors.lastname: Zemlan
authors.forename: A Z
authors.initials: AZ
authors.lastname: Murphy
authors.forename: M M
authors.initials: MM
authors.lastname: Behbehani
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D002065:Buspirone / Q000494:pharmacology; D004558:Electric Stimulation; D007478:Iontophoresis; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D002065:Buspirone