Ll. Moroz et R. Gillette, FROM POLYPLACOPHORA TO CEPHALOPODA - COMPARATIVE-ANALYSIS OF NITRIC-OXIDE SIGNALING IN MOLLUSCA, Acta biologica Hungarica, 46(2-4), 1995, pp. 169-182
The distribution of putative nitric oxide synthase (NOS)-containing ce
lls has been analysed using NADPH-d histochemistry in the CNS and peri
pheral tissues in more than 20 ecologically and systematically differe
nt molluscan genera representing 3 main classes of the phylum MOLLUSCA
: Polyplacophora (Lepidopleurus, Lepidozona, Katharina), Gastropoda (L
ittorina, Lymnaea, Aplexa, Physa, Planorbarius, Planorbis, Helisoma, B
iomphalaria, Helix, Limax, Cepaea, Bulla, Aplysia, Phyllaplysia, Phili
ne, Pleurobranchaea, Tritonia Armina, Flabellina, Cadlina) and Cephalo
poda (Octopus, Sepia, Rossia, Loligo). Several species were used for m
ore detailed immunohistochemical, biochemical, biophysical and physiol
ogical studies to further assay of NOS activity and to analyse functio
nal roles of nitric oxide (NO) in these animals. The main conclusions
of our comparative analysis and literature survey can be summarised as
following: (i) There is strong evidence for the presence of NO-depend
ent signalling pathways in different molluscan species. (ii) We hypoth
esise that a general tendency in the evolution of NADPH-d-reactive cel
ls in Mollusca is a migration of nitrergic function from periphery to
the CNS. Also, different isoforms of NOS appear to be present in any o
ne species. (iii) One of the Min functional targets of NO signalling i
s the feeding system. However, there are obvious differences between p
redators (many labelled central motoneurons) and herbivorous species (
many labelled peripheral putative sensory cells) as well as between la
nd/freshwater and marine animals. Nevertheless, in all Species tested
NO-activated feeding-like motor patterns in the buccal ganglia. Additi
onal functional and cellular targets for NO in molluscs are also consi
dered. We briefly review neuromodulatory mechanisms of NO action and w
e consider molluscs as useful model systems for investigations of the
roles of NO.