Chronotropic and dromotropic components of cardiac reflexes in the cat.

The relationship between dromotropic and chronotropic components of various cardiac reflexes was studied in cats. Intravenous infusion of blood was mainly accompanied by unidirectional negative chronotropic and dromotropic effects, but the dynamics of these effects was different. Clumping of the carotid arteries in most animals induced unidirectional negative chronotropic and dromotropic effects. Their dynamics was also different and differed from that observed during intravenous blood infusion. Pulsatile increase in blood pressure in the carotid artery was accompanied by a unidirectional negative effect in the majority of animals. The opposite chronotropic and dromotropic effects with similar temporal dynamics were revealed in 1/3 animals. The ratio of positive and negative effects was similar during clumping of the abdominal aorta (1/3 unidirectional, 1/3 opposite, and 1/3 isolated chronotropic and dromotropic effects). Aschner test was characterized by the prevalence of isolated chronotropic effect (negative effect in the majority of animals; positive effect in 1/3 animals). Hence, different cardiac reflexes are characterized by different ratio between chronotropic and dromotropic components.