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Neuromodulator Permeability of a Ganglionic Sheath in the Lobster, Homarus americanus
Author(s) -
Keller L,
Christie A,
Dickinson P
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.686.12
Subject(s) - stomatogastric ganglion , proctolin , homarus , biophysics , neuropeptide , biology , ventral nerve cord , chemistry , anatomy , microbiology and biotechnology , medicine , nervous system , neuroscience , crustacean , biochemistry , rhythm , receptor , ecology , central pattern generator
Rhythmic movements, controlled by hard‐wired neuronal networks, must be flexible in order to respond to environmental changes. Neuromodulators, released either locally within the nervous system or hormonally, provide one source of flexibility. The pyloric motor pattern, which is generated in the lobster stomatogastric ganglion (STG) and controls rhythmic movements of the foregut, is extensively modulated by neuropeptides. However, the STG is encased in a connective tissue sheath that can limit access to the ganglion; medium‐sized, hydrophobic crustacean cardioactive peptide can permeate the sheath but large, hydrophilic Val 1 ‐SIFamide cannot. We hypothesize that size and hydrophobicity, which can be combined as total polar surface area (TPSA), are two factors that dictate this selective permeability. The pyloric pattern was recorded extracellularly in the isolated stomatogastric nervous system. Neuropeptides spanning a range of TPSA values were superfused over the STG; the threshold concentration for activation and the intensity of activation for each peptide were compared with the sheath intact and after its removal. The modulatory threshold for both red pigment concentrating hormone, a large, hydrophobic peptide with a medium TPSA, and proctolin, a small, hydrophilic peptide with a small TPSA, was between 10 ‐9 and 10 ‐8 M both with and without the sheath present. However, the intensity of activation for proctolin was greater without the sheath than with, indicating the sheath may partially block proctolin. These results suggest that TPSA is a possible determinant of the permeability of the connective tissue sheath encasing the STG. Support: APS UGSRF, NIH 5P20‐RR‐016463, 8P20‐GM‐103423 (INBRE)