The uptake and release of serotonin and dopamine associated with locust (Locusta migratoria) salivary glands

The uptake and release characteristics of dopamine and serotonin in the salivary glands of the locust Locusta migratoria were examined. Cyclic AMP levels were determined in salivary glands in which the salivary nerve was stimulated under different experimental paradigms. Stimulation of the salivary nerve leads to time- and frequency-dependent elevations of cyclic AMP levels in the glands. The potent and specific D1 receptor antagonist SCH-23390 is capable of partially inhibiting the electrophysiologically induced elevations of cyclic AMP levels. The salivary glands appear to possess uptake transporters for serotonin and dopamine. [3H]serotonin uptake is Na+-dependent and is composed of high- and low-affinity components. [3H]dopamine uptake is Na+-independent and can be partially reduced by a challenge with high-K+ saline and by a challenge with ice-cold saline. Uptake inhibitors are capable of blocking the uptake of radiolabelled serotonin and dopamine. There is a Ca2+-dependent efflux of [3H]serotonin and [3H]dopamine from previously loaded salivary glands in response to stimulation of the salivary nerve and to treatment with a high-K+ saline.