5HT2 and 5HT3 receptors' contribution to modeling of post-serotonin respiratory pattern in cats

Abstract Cardio-respiratory reflex effects of an exogenous serotonin challenge are suggested to be modulated by activation of the peripheral 5HT 2 and 5HT 3 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 ), 5HT 2 receptor antagonist, shortened the duration of post-serotonin apnea (P 3 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 2 receptors. Inactivation of 5HT 3 receptors with MDL attenuated the fall in blood pressure (P 3 receptors.