Electrophysiological responses to salts from antennal chaetoid taste sensilla of the ground beetle Pterostichus aethiops

• Published in: Journal of insect physiology 2004-11, Vol.50 (11), p.1001-1013
• Main Authors: Merivee, Enno, Renou, Michel, Mänd, Marika, Luik, Anne, Heidemaa, Mikk, Ploomi, Angela
• Format: Article
• Language: English
• Subjects: Acid salts; Action Potentials; Alkaline salts; Animals; Anions; antennae; Calcium Chloride; Carabidae; cations; chemical composition; chemoreceptors; Coleoptera - physiology; Divalent cations; electrophysiology; Electrophysiology - methods; Firing rate; gustatory sensilla; ionic composition; Monovalent cations; Neutral salts; Physical Stimulation; Pterostichus; Pterostichus aethiops; Salt cell; salt cells; salt concentration; Salts; sensilla; sensory neurons; Single-Sensillum recording; Sodium Chloride; Taste; Taste Buds - physiology; taste sensitivity
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2004.09.001

Antennal gustatory sensilla of the ground beetle Pterostichus aethiops (Pz., 1797) (Coleoptera, Carabidae) respond to salts, the three sensory cells, A-, B- and C-cells, producing action potentials that are distinguished by differences in their shape, amplitude, duration and polarity of spikes. The B-cell (salt cell) was highly sensitive to both ionic composition and concentration of the tested nine salt solutions showing phasic-tonic type of reaction with a pronounced phasic component. The stimulating effect was dominated by the cations involved, and in most cases, monovalent cations were more effective stimuli than divalent cations. Salt concentration/response relations were tested with NaCl at 1, 10, 100 and 1000 mmol l −1: mean firing rates increased from 0.8 to 44 spikes per first second of the response, respectively. The pH value of the stimulating solutions also influenced the B-cell rate of firing. By contrast, the pH level of stimulus solutions influenced the A-cells’ phasic-tonic response more than the ionic composition or concentration of these solutions. Compared to a standard 100 mmol l −1 salt (NaCl) solution (pH 6.3), alkaline solutions of the salts NaCH 3COO, Na 2HPO 4 and Na 2B 4O 7 (pH 7.9, 8.5 and 9.3, respectively, all 100 mmol l −1) induced remarkably stronger responses in the A-cell. On the other hand, the reaction to an acid solution of NaH 2PO 4 (pH 4.5, 100 mmol l −1) was minimal. A-cell responses to neutral salts like NaCl, KCl, CaCl 2, MgCl 2 and C 5H 14NOCl (pH 6.1–6.5) varied largely in strength. Very low or no responses were observed with chlorides of divalent cations, CaCl 2 and MgCl 2, and choline chloride (C 5H 14NOCl), indicating that the ionic composition of the solutions also affected A-cell responses. Neural activity of the C-cell was not influenced by the salt solutions tested.