Dopamine System Components in Neuroendocrine Complexes in Snail Atrium

Abstract

Catecholamine dopamine (DA) is an important neurotransmitter and hormone involved in many physiological processes and stress reactions in vertebrates and invertebrates. The aim of the work was to clarify the presence and localization of dopamine system elements (tyrosine hydrokinase (TH), dopamine beta-hydrokinase (DAbetaHK), and dopamine type 1 receptors (DA-R1)) in the Achatina achatina gastropod atrial neuroendocrine complex (NEC) cells. The snail atrial NEC cells are generated by large granular cells (GCs) and nerve fibers that are in close contact with them. The methods of histochemistry, immunofluorescence staining, and immunoelectron microscopy were used. Glyoxylic acid-induced fluorescence demonstrated the presence of catecholamines in the nerve fibers and GC. TH-like and DAbetaH-like immunoreactive material was found both in nerve fibers and in GC granules. DA-R1-positive material was detected only in nerve fibers. In addition, it was demonstrated that exogenous DA induces an enhanced degranulation of GC in vivo. Data obtained indicate the involvement of dopamine system in the functioning of snail NEC.