c-Fos induction in the rostroventrolateral medulla by 5-HT3 receptor activation in the nucleus tractus solitarius.
The nucleus tractus solitarius (NTS) plays a crucial role in the reflex control of sympathetic tone through direct projections to the caudal and rostral regions of the ventrolateral medulla (CVLM and RVLM respectively). 5-HT3 receptor stimulation in the NTS increases both blood pressure and sympathetic tone. In order to investigate whether the ventrolateral medulla participates in these effects, the expression of c-Fos protein, a marker of neuronal activation, was examined at this level after intra-NTS microinjections of 1-(m-chlorophenyl)-biguanide, a selective 5-HT3 receptor agonist. A marked increase (93%) in the density of c-Fos-immunoreactive neurons was restricted to the most rostral part of the RVLM after this treatment. This effect could be prevented by prior intra-NTS microinjection of ondansetron, a selective 5-HT3 antagonist. These results suggest the participation of sympathoexcitatory neurons in the rostral RVLM in the pressor response to 5-HT3 receptor stimulation in the NTS.
Nosjean
A
A
INSERM U288, NeuroPsychoPharmacologie, Faculté de Médecine Pitié-Salpêtrière, Paris, France.
Hamon
M
M
Laguzzi
R
R
D000704:Analysis of Variance; D000818:Animals; D001645:Biguanides / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000378:metabolism; D008845:Microinjections; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D017552:Solitary Nucleus / Q000187:drug effects* / Q000378:metabolism
D001645:Biguanides; D016760:Proto-Oncogene Proteins c-fos; D017366:Serotonin Receptor Agonists; C065734:1-(3-chlorophenyl)biguanide