Fos expression in the NTS in response to peripheral chemoreflex activation in awake rats.
Chemoreflex afferent fibers terminate in the nucleus tractus solitarii (NTS), but the specific location of the NTS neurons excited by peripheral chemoreflex activation remains to be characterized. Here, the topographic distribution of chemoreflex sensitive cells at the commissural NTS was evaluated. To reach this goal, Fos-immunoreactive neurons (Fos-ir) were accounted in rostro-caudal levels of the intermediate and caudal commissural NTS, after intermittent chemoreflex activation with intravenous injection of potassium cyanide [KCN (80microg/kg) or saline (0.9%, vehicle), one injection every 3min during 30min]. In response to intermittent intravenous injections of KCN, a significant increase in the number of Fos-ir neurons was observed specifically in the lateral intermediate commissural NTS [(LI)NTS (82+/-9 vs. 174+/-16, cell number mean per section)] and lateral caudal commissural NTS [(LC)NTS (71+/-9 vs. 199+/-18, cell number mean per section)]. To evaluate the influence of baroreceptor-mediated inputs following the increase in blood pressure during intermittent chemoreflex activation, we performed an intermittent activation of the arterial baroreflex by intravenous injection of phenylephrine [1.5microg/kg iv (one injection every 3min during 30min)]. This procedure induced no change in Fos-ir in (LI)NTS (64+/-6 vs. 62+/-12, cell number mean per section) or (LC)NTS (56+/-15 vs. 77+/-12, cell number mean per section). These data support the involvement of the commissural NTS in the processing of peripheral chemoreflex, and provide a detailed characterization of the topographical distribution of activated neurons within this brain region.
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
Josiane de Campos
Jde C
Cruz
Leni G H
LG
Bonagamba
Javier E
JE
Stern
Benedito H
BH
Machado
D058646:Adrenergic alpha-1 Receptor Agonists; D000344:Afferent Pathways; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D001931:Brain Mapping; D003603:Cytotoxins / Q000008:administration & dosage / Q000633:toxicity; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity; D017933:Peripheral Nervous System / Q000187:drug effects / Q000502:physiology*; D010656:Phenylephrine / Q000008:administration & dosage / Q000494:pharmacology; D011190:Potassium Cyanide / Q000008:administration & dosage / Q000633:toxicity; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013268:Stimulation, Chemical; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology; D014851:Wakefulness
D058646:Adrenergic alpha-1 Receptor Agonists; D003603:Cytotoxins; D016760:Proto-Oncogene Proteins c-fos; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D011190:Potassium Cyanide