Drugs affecting phospholipase C-mediated signal transduction block the olfactory cyclic nucleotide-gated current of adult zebrafish. Li Ma and William C. Michel. University of Utah School of Medicine, Department of Physiology, 410 Chipeta Way, Salt Lake City, Utah 84108.
APStracts 4:345N, 1997.
ABSTRACT
Amino acid and bile salt odorants are detected by zebrafish using relatively independent odorant receptors but the transduction cascade(s) subsequently activated by these odorants remains unknown. Electro-olfactogram recording methods were used to determine the effects of two drugs, reported to affect PLC/IP3-mediated olfactory transduction in other vertebrate species, on amino acid and bile salt-evoked responses. At the appropriate concentrations, either an IP3-gated channel blocker, ruthenium red (0.01-0.1 (M), or a PLC inhibitor, neomycin (50 (M), reduced amino acid-evoked responses to a significantly greater extent than bile salt-evoked responses. Excised patch recording techniques were used to measure the affects of these drugs on second messenger-activated currents. Ruthenium red and neomycin are both effective blockers of the olfactory cyclic nucleotide-gated (CNG) current. Both drugs blocked the CNG channel in a voltage-dependent and reversible manner. No IP3- activated currents could be recorded. The differential effects of ruthenium red and neomycin on odor-evoked responses suggest the activation of multiple transduction cascades. The non-specific actions of these drugs on odor- activated transduction pathways and our inability to record an IP3-activated current does not permit the conclusion that zebrafish, like other fish species, use a PLC/IP3-mediated transduction cascade in the detection of odorants. 

Received 9 September 1997; accepted in final form 20 November 1997.
APS Manuscript Number J476-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997