Involvement of α- and β-adrenoreceptors in the central action of norepinephrine on temperature, metabolism, heart and respiratory rates of the conscious primate

The effect of the central blockade of alpha- and beta-adrenoreceptors on the action of norepinephrine (NE) infused by the intracerebroventricular (ICV) route was examined in the unanesthetized primate. After cannulae for ICV infusion were implanted sterotaxically, each monkey (Macaca fasicularis) was placed in a restraint chair fitted with a transparent dome for measurement of O2 uptake. During an experiment, the following responses were monitored simultaneously on a polygraph: skin and colonic temperatures, heart and respiratory rates, and metabolic rates as reflected by O2 uptake. Following an ICV infusion of 150 micrograms NE, colonic temperature, heart and metabolic rates declined while skin temperature increased and respiratory rate remained unchanged. Pretreatment with ICV phentolamine (100 micrograms), an alpha-adrenoreceptor antagonist, attenuated the changes in temperature, heart and metabolic rates and reduced respiratory rate. Similar ICV infusion of 100 micrograms propranolol, a beta-adrenoreceptor antagonist, tended also to attenuate the responses induced by NE, but overall was much less efficacious than phentolamine. Our results indicate that although catecholaminergic neurons mediate these vital physiological processes principally by central alpha-adrenoreceptors, a substantial beta-adrenoreceptor component also participates in the mechanism responsible for specific functional changes.