Fig. 5.

Effect of inhibition of the nucleus ambiguus (nAmb) on UCN1-induced bradycardic responses elicited from the ARCN. The top trace shows pulsatile arterial pressure (PAP; in mmHg), the middle trace shows MAP (in mmHg), and the bottom trace shows HR (in beats/min). A: microinjection of NMDA (10 mM) into the ARCN elicited decreases in PAP and MAP and increases in HR. After blood pressure (BP) and HR recovered to baseline levels, aCSF was microinjected into the ARCN, and no changes were observed (not shown). B: 20 min later, microinjection of UCN1 (1 mM) into the ARCN elicited decreases in PAP, MAP, and HR. C: 60 min later, the nAmb was identified with l-glutamate (l-Glu; 5 mM), and a decrease in HR was elicited with no changes in PAP and MAP. After the recovery of HR, aCSF was microinjected into the nAmb, and no changes were observed (not shown). Five minutes later, muscimol (1 mM) was microinjected into the nAmb, and an increase in HR was elicited (not shown): D: 5 min later, microinjection of UCN1 (1 mM) into the ARCN failed to elicit decreases in HR, whereas decreases in PAP and MAP persisted.