Introduction: Two distinct types of spontaneous electrical activity can be recorded from the guinea-pig prostate, slow waves and pacemaker potentials. Slow waves arise from smooth muscle cells while pacemaker potentials are believed to arise from prostatic interstitial cells (PICs). These c-kit positive cells are mainly located between the glandular epithelial and smooth muscle layers of the guinea-pig prostate and provide the depolarising pulse to neighbouring smooth muscle cells to initiate slow waves. Aim and Methods: In this study the effects of phenylephrine on the spontaneous electrical activity in the guinea-pig prostate was investigated using intracellular microelectrodes to record changes in membrane potentials. Paired Student’s t-test was used for tests of significance, values are expressed as mean ± SEM and p<0.05 was considered to be significant. Results: Phenylephrine (1μM) increased the frequency of slow wave activity from 3.9 ± 0.9 min^-1 to 9.4 ± 2.2 min^-1 (n=6, p<0.05) and pacemaker activity from 6.8 ± 1.0 min^-1 to 9.0 ± 0.9 min^-1 (n=3, p<0.05) without affecting other measured parameters. In the presence of nifedipine (1μM), phenylephrine also increased the frequency of both waveforms and in addition caused a membrane depolarisation from -53.4 ± 1.7 mV to -51.0 ± -1.9 mV in slow waves (n=8, p<0.05) and -51.4 ± 2.8 mV to -47.6 ± 2.5 mV in pacemaker potentials (n=3, p<0.05). In cells where nifedipine abolished the spontaneous electrical activity, phenylephrine was able to restore activity which was associated with a resting membrane depolarisation of 2-4mV (n=7, p<0.05). In the presence of nifedipine, cyclopiazonic acid (CPA, 10μM), carbonyl cyanide 3-chlorophenylhydrazone (CCCP, 1-10μM) or niflumic acid (10-100μM) abolished electrical activity. In the presence of CPA or CCCP, phenylephrine further depolarised the membrane potential by 6mV (n=5, p<0.05) and 4mV (n=5, p<0.05), respectively, however, was unable to restore the abolished electrical activity. Phenylephrine restored the electrical activity blocked by niflumic acid, with most measured parameters comparable to those in nifedipine alone. Conclusion: Altogether, these results suggest that the increased slow wave frequency observed by the addition of phenylephrine is likely due to its effects on PICs as phenylephrine increased the frequency of both pacemaker potentials and slow waves. The effects of phenylephrine were dependent upon Ca²⁺ cycling by internal Ca²⁺ stores within the endoplasmic reticulum and mitochondria, but not by the activation of Cl^– channels.