Responses of cerebral GABA-containing CBM neuron to taste stimulation with seaweed extracts inAplysia kurodai

The simpler nervous systems of certain invertebrates provide opportunities to examine colocalized classical neurotransmitters in the context of identified neurons and well defined neural circuits. This study examined the distribution of γ-aminobutyric acid-like immunoreactivity (GABAli) in the nervous system of the panpulmonates Biomphalaria glabrata and Biomphalaria alexandrina, major intermediate hosts for intestinal schistosomiasis. GABAli neurons were localized in the cerebral, pedal, and buccal ganglia of each species. With the exception of a projection to the base of the tentacle, GABAli fibers were confined to the CNS. As GABAli was previously reported to be colocalized with markers for dopamine (DA) in five neurons in the feeding network of the euopisthobranch gastropod Aplysia californica (Díaz-Ríos, Oyola, & Miller, 2002), double-labeling protocols were used to compare the distribution of GABAli with tyrosine hydroxylase immunoreactivity (THli). As in Aplysia, GABAli-THli colocalization was limited to five neurons, all of which were located in the buccal ganglion. Five GABAli-THli cells were also observed in the buccal ganglia of two other intensively studied panpulmonate species, Lymnaea stagnalis and Helisoma trivolvis. These findings indicate that colocalization of the classical neurotransmitters GABA and DA in feeding central pattern generator (CPG) interneurons preceded the divergence of euopisthobranch and panpulmonate taxa. These observations also support the hypothesis that heterogastropod feeding CPG networks exhibit a common universal design.

Section: Discussionmentioning

confidence: 99%

Section: Buccal Ganglia Of Lymnaea Stagnalis and Helisoma Trivolvismentioning

confidence: 99%

GABA‐like immunoreactivity in Biomphalaria: Colocalization with tyrosine hydroxylase‐like immunoreactivity in the feeding motor systems of panpulmonate snails

Vaasjo

Quintana

Habib

et al. 2018

“…The vast majority of the GABA‐ir fibers and axons in the buccal ganglia of Nudipleura are restricted to the buccal connectives, the commissures; the neuropil region of each hemiganglion; and there is very limited GABAergic innervation of the periphery. In nudibranchs, a maximum of two GABA‐ir neurons from Ce ɣL cluster of the cerebral ganglia have axons in the CBC (Gunaratne et al, ) and GABA‐ir cerebral–buccal neurons have been shown to play important roles in initiating and regulating feeding behavior in species such as Aplysia californica (Jing et al, ; Wu et al, ), Aplysia kurodai (Narusuye et al, ), and Clione limacina (Norekian and Malyshev, ). We observed two or more GABA‐ir fibers in the CBC of all the Nudipleura species, and one of the sources of these axons may be GABA‐ir buccal–cerebral neurons.…”

Section: Discussionmentioning

confidence: 99%

Comparative Mapping of GABA‐Immunoreactive Neurons in the Buccal Ganglia of Nudipleura Molluscs

Gunaratne

Katz

2015

Phylogenetic comparisons of neurotransmitter distribution are important for understanding the ground plan organization of nervous systems. This study describes the γ-aminobutyric acid (GABA)-immunoreactive (GABA-ir) neurons in the buccal ganglia of six sea slug species (Mollusca, Gastropoda, Euthyneura, Nudipleura). In the nudibranch species, Hermissenda crassicornis, Tritonia diomedea, Tochuina tetraquetra, and Dendronotus iris, the number of GABA-ir neurons was highly consistent. Another nudibranch, Melibe leonina, however, contained approximately half the number of GABA-ir neurons. This may relate to its loss of a radula and its unique feeding behavior. The GABA immunoreactivity in a sister group to the nudibranchs, Pleurobranchaea californica, differed drastically from that of the nudibranchs. Not only did it have significantly more GABA-ir neurons but it also had a unique GABA distribution pattern. Furthermore, unlike the nudibranchs, the Pleurobranchaea GABA distribution was also different from that of other, more distantly related, euopisthobranch and panpulmonate snails and slugs. This suggests that the Pleurobranchaea GABA distribution may be a derived feature, unique to this lineage. The majority of GABA-ir axons and neuropil in the Nudipleura were restricted to the buccal ganglia, commissures, and connectives. However, in Tritonia and Pleurobranchaea, we detected a few GABA-ir fibers in buccal nerves that innervate feeding muscles. Although the specific functions of the GABA-ir neurons in the species in this study are not known, the innervation pattern suggests these neurons may play an integrative or regulatory role in bilaterally coordinated behaviors in the Nudipleura.

“…The Aplysia GABA‐ir neurons in this region that project to the buccal ganglion via the CBC were identified as the cerebral buccal interneurons, CBI‐3 and CBI‐11, both of which are involved in feeding behavior (Jing et al, ; Wu et al, ). A homologous neuron to the GABA‐ir CBI‐3 neuron was also found in the related Aplysiid, Aplysia kurodai (Narusuye et al, ). Clione also contains an identified feeding neuron (Cr‐BM) that is GABA‐ir, located in the anterior lateral cerebral ganglion, and projected to the buccal ganglia via the CBC (Norekian and Malyshev, ).…”

Section: Discussionmentioning

confidence: 99%

Comparative mapping of GABA‐immunoreactive neurons in the central nervous systems of nudibranch molluscs

Gunaratne

Sakurai

Katz

2014

The relative simplicity of certain invertebrate nervous systems, such as those of gastropod molluscs, allows behaviors to be dissected at the level of small neural circuits composed of individually identifiable neurons. Elucidating the neurotransmitter phenotype of neurons in neural circuits is important for understanding how those neural circuits function. In this study, we examined the distribution of γ-aminobutyric-acid;-immunoreactive (GABA-ir) neurons in four species of sea slugs (Mollusca, Gastropoda, Opisthobranchia, Nudibranchia): Tritonia diomedea, Melibe leonina, Dendronotus iris, and Hermissenda crassicornis. We found consistent patterns of GABA immunoreactivity in the pedal and cerebral-pleural ganglia across species. In particular, there were bilateral clusters in the lateral and medial regions of the dorsal surface of the cerebral ganglia as well as a cluster on the ventral surface of the pedal ganglia. There were also individual GABA-ir neurons that were recognizable across species. The invariant presence of these individual neurons and clusters suggests that they are homologous, although there were interspecies differences in the numbers of neurons in the clusters. The GABAergic system was largely restricted to the central nervous system, with the majority of axons confined to ganglionic connectives and commissures, suggesting a central, integrative role for GABA. GABA was a candidate inhibitory neurotransmitter for neurons in central pattern generator (CPG) circuits underlying swimming behaviors in these species, however none of the known swim CPG neurons were GABA-ir. Although the functions of these GABA-ir neurons are not known, it is clear that their presence has been strongly conserved across nudibranchs.