title: Increased sympathetic nerve discharge without alteration in the sympathetic baroreflex response by serotonin3 receptor stimulation in the nucleus tractus solitarius of the rat.
abstract: Previous studies have shown that serotonin3 receptor activation in the nucleus tractus solitarius (NTS) increased mean arterial pressure (MAP) and inhibited the cardiac component of the baroreceptor reflex [9]. We have examined the effects of such stimulation upon spontaneous and evoked sympathetic nerve activity. Microinjection of serotonin (10 nmol) into the NTS of halothane-anaesthetized, paralyzed and artificially ventilated rats produced an increase in MAP and lumbar sympathetic nerve discharge which could be completely prevented by prior local microinjection of zacopride, a potent serotonin3 antagonist (200 pmol). In addition, 1-(m-chlorophenyl)-biguanide, a selective serotonin3 receptor agonist, mimicked the sympathoexcitatory effect of serotonin. Since the gain of the sympathetic component of the baroreflex was unaltered after intra-NTS microinjection of serotonin, it could be concluded that serotonin3 receptors activation in the NTS induces a sympathetic activation which is not mediated through an inhibition of the sympathetic baroreceptor reflex arc.
authors.affiliation: INSERM U288, Neurobiologie Cellulaire et Fonctionnelle, Faculté de Médecine Pitié-Salpêtrière, Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Nosjean
authors.forename: B
authors.initials: B
authors.lastname: Franc
authors.forename: R
authors.initials: R
authors.lastname: Laguzzi
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D008297:Male; D008845:Microinjections; D011311:Pressoreceptors / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects*
chemical_list: D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin