title: [Beta-1 adrenoceptor blockade decreases the firing rate to painful stimuli in spinal wide-dynamic range neurons in rats].
abstract: BACKGROUND
  It is known that epinephrine/norepinephrine inhibit acute pain transmission. However, the role of ß-adrenoceptors is not clear. Thus, we analyzed if beta-1 and/or beta-2 adrenoceptors can modulate acute pain transmission by performing in vivo single unit recordings during painful and non-painful peripheral stimulation in rats.
  
  
  METHODS
  Longitudinal study in which we analyzed seven groups of male rats Wistar: control group (n = 11): saline (0.9 %); EPI group (n = 8): epinephrine 100 mcg; beta-1 agonist group (n = 8): dobutamine 125 mcg; beta-1-antagonist group (n = 9): metoprolol 100 mcg; beta-2-agonist group (n = 7): clenbuterol 100 mcg; beta-2-antagonist group (n = 8): butoxamine 100 mcg; beta-1-antagonist + EPI group (n = 10): metoprolol 100 mcg + epinephrine 100 mcg. For the statistical analysis we used ANOVA.
  
  
  RESULTS
  Epinephrine significantly reduced the basal firing rate (BFR) in 34.1 % (p < 0.05) and also the evoked response by painful stimulation in 56 % (p < 0.05). No change was observed in the evoked response by non-painful stimulation. ANTß1 was the only beta-adrenoceptor acting drug that significantly reduced the evoked response by painful stimulation in 41 % (p < 0.05). None of the other drugs alone affected either the BFR or the evoked response to non-painful or painful stimulation.
  
  
  CONCLUSIONS
  It is the first time that a beta-1-adrenoceptor antagonist (metoprolol) probes to be effective in reducing the response to painful stimulation in WDR neurons.
authors.affiliation: Laboratorio de Neurofisiología de la Percepción, Instituto Nacional de Psiquiatría "Ramón de la Fuente Muñiz", Distrito Federal, México. neuropercepcion@gmail.com.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lamothe-Molina
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Lamothe-Molina
authors.forename: Alberto
authors.initials: A
authors.lastname: López-Ávila
mesh_terms: D058671:Adrenergic beta-1 Receptor Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D055724:Electrophysiological Phenomena / Q000187:drug effects; D008297:Male; D008790:Metoprolol / Q000494:pharmacology / Q000627:therapeutic use*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000188:drug therapy*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D008790:Metoprolol
keywords: Acute pain; Beta-Blockers, Adrenergic; Metroprolol; Receptors, Adrenergic