The onset of sympathetic innervation has been shown to play a role in the development of postsynaptic reactivity to stimulation. In the current study, we examined whether this relationship extends to responses evoked by hormonal stimuli. Rats denervated at birth by 6-hydroxydopamine treatment showed an impaired ability of vasopressin or angiotensin to stimulate cardiac ornithine decarboxylase activity. In the kidney, responsiveness was affected only for vasopressin and in the lung denervation had only transient effects on the hormonal responses. These results confirm that sympathetic input is required for proper development of some, but not all hormonal responses; the tissue specificity suggests a role of neural factors selective for cardiac development.