title: Acetylcholine receptors in spider peripheral mechanosensilla.
abstract: Peripherally located parts of spider mechanosensory neurons are modulated by several neurotransmitters released from apposed efferent fibers. Activities of acetylcholine (ACh) synthesizing enzyme choline acetyltransferase (ChAT) and ACh degrading enzyme acetylcholine esterase (AChE) were previously found in some efferent fibers. ChAT activity was also present in all the mechanosensory neurons, while AChE activity was only found in some. We show that spider mechanosensory neurons and probably some efferent neurons are immunoreactive to a monoclonal antibody against muscarinic ACh receptors (mAChRs). However, application of muscarinic agonists did not change the physiological responses or membrane potentials of neurons in the lyriform organ VS-3. Similarly, the sensitivities of the neurons of trichobothria (filiform hairs) remained unchanged after application of these agonists. Therefore, activation of mAChRs may only modulate the function of spider mechanosensory neurons indirectly, for example, by affecting the release of other transmitter(s). However, a subgroup of VS-3 neurons was inhibited by ACh, which also depolarized the membrane similar to these neurons' responses to GABA, suggesting that ACh activates anion channels in these neurons. Interestingly, all of the neurons responding to ACh were the rapidly adapting Type A neurons that were previously shown to express AChE activity.
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, B3H 1X5 Halifax, Nova Scotia, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Widmer
authors.forename: Izabela
authors.initials: I
authors.lastname: Panek
authors.forename: Ulli
authors.initials: U
authors.lastname: Höger
authors.forename: Shannon
authors.initials: S
authors.lastname: Meisner
authors.forename: Andrew S
authors.initials: AS
authors.lastname: French
authors.forename: Päivi H
authors.initials: PH
authors.lastname: Torkkeli
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D008465:Mechanoreceptors / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D018721:Muscarinic Agonists / Q000494:pharmacology; D009475:Neurons, Afferent / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D009476:Neurons, Efferent / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology; D010095:Oxotremorine / Q000031:analogs & derivatives / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000502:physiology*; D013112:Spiders / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D018721:Muscarinic Agonists; D018377:Neurotransmitter Agents; D011950:Receptors, Cholinergic; D005680:gamma-Aminobutyric Acid; D010095:Oxotremorine; C042743:oxotremorine M; D000109:Acetylcholine