The Journal of Neurophysiology Vol. 77 No. 5 May 1997, pp. 2235-2251
Copyright ©1997 The American Physiological Society

Ionotropic GABA Receptor From Lobster Olfactory Projection Neurons

A. B. Zhainazarov¹, M. Wachowiak^{1, 3}, A. Boettcher¹, S. Elenes¹, and B. W. Ache^{1, 2, 3}

¹ Whitney Laboratory and ² Department of Zoology and ³ Department of Neuroscience, University of Florida, St. Augustine, Florida 32086

Zhainazarov, A. B., M. Wachowiak, A. Boettcher, S. Elenes, and B. W. Ache. Ionotropic GABA receptor from lobster olfactory projection neurons. J. Neurophysiol. 77: 2235-2251, 1997. This study reports an ionotropic GABA (-aminobutyric acid) receptor in projection neurons acutely dissociated from the olfactory lobe of the brain of the spiny lobster and analyzed by whole cell and cell-free patch-clamp recording. GABA evokes a macroscopic current in the cells that is linear from 100 to +100 mV, reverses at the imposed chloride equilibrium potential, has a permeability sequence of Cl > acetate > bicarbonate > phosphate > propionate and SCN > Br > I > Cl > F, and is reversibly blocked by the Cl channel blocker picrotoxin but not tert-butylbicyclophosphorothionate (TBPS). The current is bicuculline insensitive and activated by muscimol, isoguvacine, cis-4-aminocrotonic acid (CACA), and trans-aminocrotonic acid (TACA), as well as by the GABA_C-receptor antagonists 4,5,6,7-tetrahydroisoxazolo [5,4,-c]pyridin-3-ol (THIP), 3-amino-1-propanesulfonic acid(3-APS), and imidazole-4-acetic acid (I-4AA), but not theGABA_B-receptor agonists baclofen and 3-aminopropylphosphonic acid (3-APA). Agonist potency for the receptor is TACA > muscimol > GABA > I-4AA > isoguvacine > 3-APS > CACA > THIP. Unitary chloride currents in cell-free, outside-out patches from the cells share enough of these pharmacological properties to indicate that the channel underlies the macroscopic current. The receptor mediates an inhibitory current in the cells in vivo. The receptor is similar, if not identical, to one from neurons cultured from the thoracic ganglia of the clawed lobster. The more extensive pharmacological characterization of the receptor reported here indicates that this lobster CNS receptor is pharmacologically distinct from previously characterized ionotropic GABA receptors.

This article has been cited by other articles:

				D. Mellon Jr. Convergence of Multimodal Sensory Input Onto Higher-Level Neurons of the Crayfish Olfactory Pathway J Neurophysiol, December 1, 2000; 84(6): 3043 - 3055. [Abstract] [Full Text] [PDF]

				M. Wachowiak and L. B. Cohen Presynaptic Inhibition of Primary Olfactory Afferents Mediated by Different Mechanisms in Lobster and Turtle J. Neurosci., October 15, 1999; 19(20): 8808 - 8817. [Abstract] [Full Text] [PDF]

				S. Yagodin, C. Collin, D. L. Alkon, N. F. Sheppard Jr., and D. B. Sattelle Mapping Membrane Potential Transients in Crayfish (Procambarus clarkii) Optic Lobe Neuropils With Voltage-Sensitive Dyes J Neurophysiol, January 1, 1999; 81(1): 334 - 344. [Abstract] [Full Text] [PDF]