Fig. 2.
The antagonism of 5-HT2 receptors blocks the emergence of abdominal activity in response to episodic microinjections of 5-HT in the RTN/pFRG of anesthetized vagotomized rats. Pulsatile arterial pressure (PAP), raw and integrated (∫) diaphragmatic (DIAEMG) and abdominal (ABDEMG) electromyographic recordings of vagotomized animals, representative from their respective group, illustrating the cardiorespiratory changes elicited by episodic 5-HT microinjections in the RTN/pFRG (A, solid arrows) that were prevented by previous 5-HT2 receptor antagonism with ketanserin (B, dashed arrow). C and D: expanded tracings from A and B, respectively, illustrating the PAP recordings and the integrated DIAEMG and ABDEMG activities before (1 and I) and at 30 (2 and II) and 60 min (3 and III) after microinjections. E–I: average values of DIA burst amplitude (E) and frequency (F), ABD mean activity (G), mean arterial pressure (MAP, H) and heart rate (HR, I) before (basal) and after microinjections of vehicle (n = 4), episodic 5-HT (n = 6) and ketanserin + episodic 5-HT (n = 5) in the RTN/pFRG. J: photomicrography of a coronal slice of the brain stem from a representative rat of the group, showing the sites of microinjections in the RTN/pFRG (arrows). VII, facial nucleus; py, pyramidal tract; RPa, raphe pallidus nucleus; sp5, spinal trigeminal tract. *Different from respective basal values, P < 0.05. #Different from vehicle group at the corresponding time, P < 0.05.