In vivo effects of fenoldopam on autonomic nervous system after inhibition or activation of ganglionic transmission. 
The study investigated the effects of dopamine D1-like receptor stimulation on the autonomic nervous system.  Fenoldopam (20 microg/kg) was injected i.v.  in conscious sinoaortic denervated dogs, that is, surgically deprived of baroreflex pathways.  In barodenervated dogs, fenoldopam (20 microg/kg) induced arterial hypotension as well as bradycardia and reduced noradrenaline plasma levels.  Pentolinium (0.1 mg/kg i.v.),  used to induce partial blockade of nicotinic ganglionic receptors, suppressed the fenoldopam-induced decrease in sympathetic tone, suggesting a ganglionic location for the dopamine D1-like receptor.  Moreover, the inability of fenoldopam to reduce the nicotine-induced increase in sympathetic tone suggests that a postsynaptic ganglionic location can be excluded for the dopamine D1-like receptor.  The results of these "in vivo" experiments strongly suggest a presynaptic location for the ganglionic dopamine D1-like receptor, stimulation of which results in a reduction of sympathetic tone.