5HT2 and 5HT3 receptors' contribution to modeling of post-serotonin respiratory pattern in cats.
Cardio-respiratory reflex effects of an exogenous serotonin challenge are suggested to be modulated by activation of the peripheral 5HT2 and 5HT3 receptors. In the present experiments the blocking effects of serotoninergic active drugs: ketanserin and tropanserin (MDL 72222) were studied in six pentobarbitone-chloralose anaesthetized cats. Bolus injection of serotonin (0.05 mg.kg(-1)) into the right femoral vein evoked prompt apnea, hypotension followed by tachypnoeic breathing. Pre-treatment with ketanserin (0.1 mg.kg(-1)), 5HT2 receptor antagonist, shortened the duration of post-serotonin apnea (P < 0.05), but had no effect on the pattern of post-apnoeic breathing. 5HT3 receptor blockade with the selective antagonist MDL 72222 (0.2 mg.kg(-1)) totally eliminated respiratory response to serotonin. In breaths that followed post-serotonin apnea, peak amplitude of the integrated phrenic signal was reduced (P < 0.001), unbiased by ketanserin blockade, and remained at the baseline level in MDL treated rats. Serotonin-induced hypotension was unaffected by the blockade of 5HT2 receptors. Inactivation of 5HT3 receptors with MDL attenuated the fall in blood pressure (P < 0.05). This data suggests that the squeal of serotonin-induced pulmonary chemoreflex, i.e. respiratory arrest, post-apnoeic pattern of breathing, bradycardia, and partially hypotension are mediated by 5HT3 receptors.
Kopczyńska
Beata
B
Laboratory of Respiration Physiology, PAS Medical Research Center, 5 Pawiñskiego St., 02-106 Warsaw, Poland. kopczynb@cmdik.pan.pl
Szereda-Przestaszewska
Małgorzata
M
D000818:Animals; D001049:Apnea / Q000503:physiopathology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001919:Bradycardia / Q000503:physiopathology; D002415:Cats; D004305:Dose-Response Relationship, Drug; D007274:Injections, Intraperitoneal; D007650:Ketanserin / Q000494:pharmacology; D007830:Larynx / Q000503:physiopathology; D008297:Male; D010791:Phrenic Nerve / Q000502:physiology; D044348:Receptors, Serotonin, 5-HT2 / Q000187:drug effects / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3 / Q000187:drug effects / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013990:Tidal Volume / Q000187:drug effects; D014326:Tropanes / Q000494:pharmacology
D044348:Receptors, Serotonin, 5-HT2; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D014326:Tropanes; D012701:Serotonin; D007650:Ketanserin; C042253:bemesetron