Figure 7. Potentiation of the chemoreceptor reflex bradycardia by ANGII in the NTS is mediated by NK₁ receptors.

A microinjection of 500 fmol ANGII into the NTS enhanced significantly the bradycardic component of the chemoreceptor reflex. This potentiation was dependent upon the integrity of NK₁ receptors since their blockade with CP-99,994 revealed an attenuation of the reflex bradycardia compared to the control response. This attenuation was reversed by losartan indicating that AT₁ receptors also caused an inhibitory effect on NTS circuitry mediating the chemoreceptor reflex. Abbreviations as in Fig. 1. NaCN (0·05%; 50 μl) was injected into the aorta.