Meeting Abstract

P1.177  Friday, Jan. 4  The Distrubution of GABAergic Neurons in The CNS of Nudibranch Molluscs CAIN, SD; ZUNGUL-HASTY, LS; KELSEY, P*; Eastern Oregon University; Eastern Oregon University; Eastern Oregon University shaun.cain@eou.edu

The neurotransmitter GABA is known to play a role in the transmission of information in the central nervous systems of many animals, including molluscs. GABA can function as an inhibitory transmitter both at metabotropic and ionotropic synapses, activating either chloride or potassium conductances. Therefore, it is thought that this neurotransmitter is typically inhibitory at GABAergic synapses. Indeed, GABA plays an inhibitory role in interactions between the visual and vestibular system in the nudibranch Hermissenda crassicornis. However, GABA can also play an excitatory role mediated by sodium conducting channels as shown in the feeding circuit of Clione limacina or through reduction of a potassium current in photoreceptors in Hermissenda. Given the different roles GABA plays in the neural circuits underlying behavior in molluscs, we investigated the distribution of GABAergic neurons in the monophyletic clade Nudibranchia. Neurons both within the brain and buccal ganglia that contain GABA were identified using immunohistochemistry. In all species we investigated, GABA-like immunoreactive neurons were found in both the brain and buccal ganglia. The distribution in the brain was variable while the number and distribution in the buccal was similar in all species (4-6 neurons per gangion). This might indicate that the role of GABA in the feeding rhythm is more highly conserved then that in other parts of the nervous system of nudibranchs.