Fig. 4

GABA-like elements in prostomium, palps and anterior body part of Pygospio elegans. a, b GABA-like elements of the palps. Yellow arrows label palp receptor cells. c Innervation of the mouth region, ventral view. d-f Partial z-projections of the brain region showing GABA-like neuronal somata (d, f) and fibers of GABA-like cells in the neuropil (e). White arrowheads – neurons at the palp base. g Innervation of the anterior part of the prostomium. h – j GABA-like elements in stomatogastric system of an intact (h) and regenerated specimens (i, j), 7 days after amputation (i lateral view, j virtual cross section through the thoracic segment). Yellow arrowheads mark neurons of the stomatogastric system. Abbreviations: dc – dorsal cerebral commissure, fpn – frontal prostomial nerve, i – intestine, ln – lateral longitudinal nerve, npc – non-receptor palp nerve cell, pcp – posterior commissure of the prostomium, phn – pharyngeal nerves, pln – palp nerve, sog – subesophageal ganglion, vc – ventral cerebral commissure. GABA-like elements – green, acetylated α-tubulin-like elements – magenta