Following sinoaortic denervation (SAD) rats present intense arterial pressure lability without sustained hypertension. This study aimed to verify the effects of heptanol (a putative gap-junction blocker) and tetraethylammonium (TEA, a putative gap-junction activator) on rhythmic contractions (RCs) and vascular reactivity in the aortas isolated from SAD and Sham-operated (SO) rats. Rhythmic contractions were observed with phenylephrine in endothelium-removed aortic rings from SAD rats. We evaluated the effects of the gap-junction modulators heptanol or TEA on the frequency and amplitude of these oscillations. Additionally, concentration–response curves were constructed to TEA and KCl and in pre-contracted arteries (with phenylephrine or KCl) to heptanol in order to verify the effects of those gap-junction modulators. Comparatively, rhythmic contractions were observed in 10/10 SAD rat aortas vs. 2/10 controls. Heptanol decreased the frequency of oscillations in a concentration-dependent manner. TEA increased the amplitude and frequency of RCs. In the experiments of concentration–response curves to TEA, the maximal contractile effect was similar in both groups, although the potency was lower in SAD than in SO rat aortas. The relaxation to heptanol was different between the groups only after pre-contraction induced by phenylephrine. Heptanol showed higher potency in SAD as compared to SO rat aortas. In conclusion, arterial pressure lability occurs only in SAD rats, and their isolated aortas exhibit intense RCs. These RCs seem to be dependent of the gap-junction communication, since these oscillations are intensified by TEA and inhibited by heptanol. After SAD, aortas are more sensitive to heptanol and less sensitive to TEA.