Aminergic cellular organization in the gills of Aplysia species

Abstract

The constituent elements of the gills of Aplysia kurodai and A. juliana were examined for the presence of biogenic amines using histochemical, immunocytochemical, and HPLC techniques. Aminergic elements were revealed by glyoxylic acid-induced fluorescence in the branchial nerve, branchial ganglion, branchial vessels, and pinnules in both species. Three types of fluorescent cells were found in the neural plexus of the gill in each species. Two of them might be sensory neurons. Although HPLC analysis showed the presence of serotonin and dopamine in all gill structures including fluorescent neural elements, there were regional differences in concentrations of the monoamines. It was noted in the pinnules that there was a much higher concentration of dopamine than serotonin. Serotonin immunocytochemistry revealed neural processes which were immunoreactive to antiserotonin antibody, but serotonin immunoreactivity could not be found in a population of branchioganglionic neuron (BGN) somata. Serotonergic elements in the ganglion may be processes of the central ganglion, while dopaminergic elements may be processes of neurons in the neural plexus, located beyond the branchial ganglion. BGNs were activated by bath-applied dopamine and serotonin. These results suggest that dopaminergic sensory inputs from the neural plexus and serotonergic descending inputs from the abdominal ganglion may be among the inputs received by BGNs. It was found that serotonin depressed excitatory junctional potentials in muscle cells of the efferent branchial vessel, which were induced by an identified neuron of the abdominal ganglion. The aminergic cellular organization of the gill may involve serotonergic presynaptic-inhibitory fibers arising from the abdominal ganglion.

Dopaminergic acceleration and GABAergic inhibition in extrinsic neural control of the hermit crab heart

“…For localizing GABA-like immunoreactive neural processes, methods previously described (Kurokawa et al 1989) were used with modifications in fixation according to Kuwasawa et al (1992). Paraffin serial sections were cut at a thickness of 10-15 lam.…”

Mosaic arrangement of SCP b -, FMRFamide-, and histamine-like immunoreactive sensory hair cells in the statocyst of the gastropod mollusc Pleurobranchaea japonica

“…The aforementioned dissected preparations were immersed in 4% carbodiimide [1-ethyl-3(3-dimethylaminopropyl)-carbodiimide] (Dojin-Wako) in PB for 1 h at room temperature, 4% paraformaldehyde in PB for 2-3 h, and rinsed in PB at 4°C. After washing with 0.1% PBT, preparations were treated using the peroxidase-antiperoxidase (PAP) method and stained with 3,3′-diaminobenzidine tetrahydrochloride (DAB; Kurokawa et al 1989), or double stained using fluorescein isothiocyanate (FITC) and tetrarhodamine isothiocyanate (TRITC) procedures. To detect serotonin and GABA, preparations were fixed with 4% paraformaldehyde in PB for 2-3 h. Fixed preparations were embedded in paraffin and sectioned one by one serially with a microtome at 3 µm, 5 µm, or 10 µm thickness.…”

Release of Dopamine from Carotid Sinus Nerve Fibers Innervating Type I Cells in the Cat Carotid Body

“…Our data, in con trast, suggest that in the cat, as in the rat, the expression of TH-IR in these sensory neurons reflects the capacity to synthesize CA, in par ticular DA. The existence of dopaminergic sensory neurons has already been reported for other sensory systems [30,31], Of course, the existence of dopaminergic vasomotor fibers, as described in other structures [25][26][27][28][32][33][34], also remains a possibility, but our bio chemical data from sympathectomized ani mals would indicate that if such autonomic dopaminergic fibers are present in the CSN, they do not originate from the SCG. Further more, our histological studies demonstrated no appreciable loss of axonal TH-IR following sympathectomy, although changes in the inci dence of very small caliber TH-positive post ganglionic elements cannot reliably be ascer tained utilizing the present immunocytochemical, light-microscopic techniques.…”

“…At the peripheral terminus of the sensory fiber, release of DA could be expected to act on DA autoreceptors present on the type I cells [39,40], much as the peripheral release of substance P from sensory nerve endings has been demonstrated to have an important physiological role in other sensory systems [41,42], In support of this possibility, Finley et al [14] recently reported the ultrastructural localization of TH-positive unmyelinated fi bers in contact with type I cells in sympathec tomized carotid bodies in the rat. A role for DA might also need to be considered in the central processing of chemoreceptor informa tion transmitted by CSN fibers, as has also been proposed for this CA in other sensory pathways [30,31 ].…”