Comparative contractile responses among ventral, dorsal, and lateral lobes of the rat prostate

Prostatic zonal heterogeneity as a factor influencing urogenital smooth muscle contractile mechanisms was evaluated in the dorsal, lateral, and ventral lobes of the sexually mature rat. Additionally, using the ventral lobe, we assessed the role of the prostatic capsule to determine its contribution to tissue contractility. Smooth muscle contractile responses were determined for the alpha-adrenergic agonists norepinephrine and methoxamine; the cholinergic agonist carbamylcholine; the alpha 2-adrenergic agonist UK-14,304; serotonin; and potassium chloride. The dorsal, lateral, and ventral lobes contracted in response to all agonists. In the three lobes, norepinephrine was the most potent contractile agent; alpha 2 receptor activation with UK-14,304 resulted in the lowest maximum response. Carbamylcholine and serotonin were only weak contractile agonists in all three lobes. Maximum contractile responses to alpha agonists were greatest in the ventral prostate relative to the other two lobes, based on contractile responses to norepinephrine and methoxamine relative to KCl. The contractions of the ventral lobe in the presence and absence of the capsule were similar; thus the observed responses were not enhanced by the capsule but were attributable primarily to the presence of prostatic smooth muscle. Insofar as these studies with anatomically distinct lobes in the rat may reflect zonal homology in other species, these results support the contention that all zones may contribute to prostatic contractility.