Indications for a hormonal function of dopamine in the central nervous system of the snail Lymnaea stagnalis

In the present paper we collected evidence for the occurrence of D2-like dopamine receptors on the cell bodies of the neuroendocrine growth hormone-producing cells (GHCs) in the central nervous system (CNS) of the snail Lymnaea stagnalis. Measurements of the membrane potential of GHCs in situ as well as isolated GHCs revealed that stimulation of these dopamine receptors results in a hyperpolarization. Although immunohistochemical analysis of the CNS of L. stagnalis clearly revealed the occurrence of dopamine containing cells and nerve fibers, no projections of dopamine immunopositive fibers to the GHC cell bodies could be observed. By using HPLC with electrochemical detection we found that the blood concentration of dopamine in L. stagnalis is in the range of concentrations hyperpolarizing GHCs in vitro (0.1-10 microM). On the basis of these findings it is proposed that dopamine is involved in hormonal communication in the CNS of L. stagnalis.