Hypertension is associated with the early onset of cardiac sympathetic hyperresponsiveness and enhanced intracellular Ca²⁺ concentration [Ca²⁺]_i in sympathetic neurons from both prehypertensive and hypertensive, spontaneously hypertensive rats (SHRs). Oxidative stress is a hallmark of hypertension, therefore, we tested the hypothesis that the inhibitory action of the nitric oxide-cGMP pathway on [Ca²⁺]_i transients is impaired in cardiac sympathetic neurons from the SHR. Stellate ganglia were isolated from young prehypertensive SHRs and age-matched normotensive Wistar-Kyoto rats. [Ca²⁺]_i was measured by ratiometric fluorescence imaging. Neurons from the prehypertensive SHR ganglia had a significantly higher depolarization evoked [Ca²⁺]_i transient that was also associated with decreased expression of neuronal nitric oxide synthase (nNOS), β1 subunit of soluble guanylate cyclase and cGMP when compared with the Wistar-Kyoto rat ganglia. Soluble guanylate cyclase inhibition or nNOS inhibition increased [Ca²⁺]_i in the Wistar-Kyoto rats but had no effect in SHR neurons. A nitric oxide donor decreased [Ca²⁺]_i in both sets of neurons, although this was markedly less in the SHR. A novel noradrenergic cell specific vector (Ad.PRSx8-nNOS/Cherry) or its control vector (Ad.PRSx8-Cherry) was expressed in sympathetic neurons. In the SHR, Ad.PRSx8-nNOS/Cherry-treated neurons had a significantly reduced peak [Ca²⁺]_i transient that was associated with increased tissue levels of nNOS protein and cGMP concentration compared with gene transfer of Ad.PRSx8-Cherry alone. nNOS inhibition significantly increased [Ca²⁺]_i after Ad.PRSx8-nNOS/Cherry expression. We conclude that artificial upregulation of stellate sympathetic nNOS via targeted gene transfer can directly attenuate intracellular Ca²⁺ and may provide a novel method for decreasing enhanced cardiac sympathetic neurotransmission.