Role of central 5-HT3 receptors in the control of blood pressure in stressed and non-stressed rats.
The aim of the present study was to investigate the participation of central 5-HT(3) receptors in the control of blood pressure and heart rate (HR) of non-stressed and stressed rats. The pharmacological stimulation of brain 5-HT(3) receptors by third ventricle injections of the selective 5-HT(3) receptor agonist m-CPBG induced a significant decrease in blood pressure in non-stressed rats and impaired the hypertensive response induced by restraint stress. The blockade of brain 5-HT(3) receptors by the central administration of the selective 5-HT(3) antagonist ondansetron elicited a significant increase in blood pressure in non-stressed rats. Conversely, the hypertensive response induced by restraint stress was not affected by central administration of ondansetron. Additionally, baroreflex-mediated bradycardia during phenylephrine-induced hypertensive response was preserved in non-stressed animals receiving third ventricle injections of m-CPBG, while the baroreflex-mediated tachycardia that occurs during the hypotensive response induced by the administration of sodium nitroprusside was impaired. It is concluded that the serotoninergic component represented by the brain 5-HT(3) receptors exerts a tonic inhibitory influence on the central control of blood pressure in non-stressed rats, probably by a sympathoinhibitory-related mechanism. On the other hand, during stress, this central 5-HT(3)-dependent inhibitory drive is overwhelmed by the different neurochemical systems that harmonically trigger and sustain the hypertensive response.
Ferreira
Hilda Silva
HS
Life Sciences Department, Bahia State University, 41195-001 Salvador, Bahia, Brazil.
de Castro e Silva
Emilio
E
Cointeiro
Carla
C
Oliveira
Elenilda
E
Faustino
Thiallan Nery
TN
Fregoneze
Josmara Bartolomei
JB
D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D001645:Biguanides / Q000008:administration & dosage; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007276:Injections, Intraventricular; D008297:Male; D017294:Ondansetron / Q000008:administration & dosage; D051381:Rats; D044406:Receptors, Serotonin, 5-HT3 / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000008:administration & dosage; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage; D013315:Stress, Psychological / Q000503:physiopathology*
D001645:Biguanides; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D017294:Ondansetron; C065734:1-(3-chlorophenyl)biguanide