The Journal of Neurophysiology Vol. 81 No. 1 January 1999, pp. 1-14
Copyright ©1999 The American Physiological Society

Cultured Insect Mushroom Body Neurons Express Functional Receptors for Acetylcholine, GABA, Glutamate, Octopamine, and Dopamine

M. Cayre, S. D. Buckingham, S. Yagodin, and D. B. Sattelle

Babraham Institute Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom

Cayre, M., S. D. Buckingham, S. Yagodin, and D. B. Sattelle. Cultured insect mushroom body neurons express functional receptors for acetylcholine, GABA, glutamate, octopamine, and dopamine. J. Neurophysiol. 81: 1-14, 1999. Fluorescence calcium imaging with fura-2 and whole cell, patch-clamp electrophysiology was applied to cultured Kenyon cells (interneurons) isolated from the mushroom bodies of adult crickets (Acheta domesticus) to demonstrate the presence of functional neurotransmitter receptors. In all cells investigated, 5 µM acetylcholine (ACh, n = 52) evoked an increase in intracellular free calcium ([Ca²⁺]_i). Similar effects were observed in response to 10 µM nicotine. The ACh response was insensitive to atropine (50 µM) but was reduced by mecamylamine (50 µM) and -bungarotoxin (-bgt, 10 µM). ACh-induced inward ion currents (n = 28, E_ACh ~0 mV) were also blocked by 1 µM mecamylamine and by 1 µM -bgt. Nicotine-induced inward currents desensitized more rapidly than ACh responses. Thus functional -bgt-sensitive nicotinic ACh receptors are abundant on all Kenyon cells tested, and their activation leads to an increase in [Ca²⁺]_i. -Aminobutyric acid (GABA, 100 µM) triggered a sustained decrease in [Ca²⁺]_i. Similar responses were seen with a GABA_A agonist, muscimol (100 µM), and a GABA_B agonist, 3-APPA (1 mM), suggesting that more than one type of GABA receptor can affect [Ca²⁺]_i. This action of GABA was not observed when the extracellular KCl concentration was lowered. All cells tested (n = 26) with patch-clamp electrophysiology showed picrotoxinin (PTX)-sensitive, GABA-induced (30-100 µM) currents with a chloride-sensitive reversal potential. Thus, an ionotropic PTX-sensitive GABA receptor was found on all Kenyon cells tested. Most (61%) of the 54 cells studied responded to L-glutamate (100 µM) application either with a biphasic increase in [Ca²⁺]_i or with a single, delayed, sustained [Ca²⁺]_i increase. Nearly all cells tested (95%, n = 19) responded to (100 µM) L-glutamate with rapidly desensitizing, inward currents that reversed at approximately 30 mV. Dopamine (100 µM) elicited either a rapid or a delayed increase in [Ca²⁺]_i in 63% of the 26 cells tested. The time course of these responses varied greatly among cells. Dopamine failed to elicit currents in patch-clamped cells (n = 4). A brief decrease in [Ca²⁺]_i was induced by octopamine (100 µM) in ~54% of the cells tested (n = 35). However, when extracellular CaCl₂ was lowered, octopamine triggered a substantial increase in [Ca²⁺]_i in 35% of the cells tested (n = 26). No octopamine-elicited currents were detected in patched-clamped cells (n = 10).

This article has been cited by other articles:

				H. Gu and D. K. O'Dowd Cholinergic Synaptic Transmission in Adult Drosophila Kenyon Cells In Situ J. Neurosci., January 4, 2006; 26(1): 265 - 272. [Abstract] [Full Text] [PDF]

				S. A. Jiang, J. M. Campusano, H. Su, and D. K. O'Dowd Drosophila Mushroom Body Kenyon Cells Generate Spontaneous Calcium Transients Mediated by PLTX-Sensitive Calcium Channels J Neurophysiol, July 1, 2005; 94(1): 491 - 500. [Abstract] [Full Text] [PDF]

				D. G. Wustenberg, M. Boytcheva, B. Grunewald, J. H. Byrne, R. Menzel, and D. A. Baxter Current- and Voltage-Clamp Recordings and Computer Simulations of Kenyon Cells in the Honeybee J Neurophysiol, October 1, 2004; 92(4): 2589 - 2603. [Abstract] [Full Text] [PDF]

				C. Wegener, Y. Hamasaka, and D. R. Nassel Acetylcholine Increases Intracellular Ca2+ Via Nicotinic Receptors in Cultured PDF-Containing Clock Neurons of Drosophila J Neurophysiol, February 1, 2004; 91(2): 912 - 923. [Abstract] [Full Text] [PDF]

				H. Su and D. K. O'Dowd Fast Synaptic Currents in Drosophila Mushroom Body Kenyon Cells Are Mediated by {alpha}-Bungarotoxin-Sensitive Nicotinic Acetylcholine Receptors and Picrotoxin-Sensitive GABA Receptors J. Neurosci., October 8, 2003; 23(27): 9246 - 9253. [Abstract] [Full Text] [PDF]

				D. Yu, G. S. Baird, R. Y. Tsien, and R. L. Davis Detection of Calcium Transients in Drosophila Mushroom Body Neurons with Camgaroo Reporters J. Neurosci., January 1, 2003; 23(1): 64 - 72. [Abstract] [Full Text] [PDF]

				S. Oleskevich Cholinergic Synaptic Transmission in Insect Mushroom Bodies In Vitro J Neurophysiol, August 1, 1999; 82(2): 1091 - 1096. [Abstract] [Full Text] [PDF]