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First published online September 19, 2006
Journal of Experimental Biology 209, 3898-3912 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02432

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Perfusion with cGMP analogue adapts the action potential response of pheromone-sensitive sensilla trichoidea of the hawkmoth Manduca sexta in a daytime-dependent manner

Christian Flecke, Jan Dolzer, Steffi Krannich and Monika Stengl^*

Biologie, Tierphysiologie, Philipps-Universität Marburg, Karl-von-Frisch-Straße, D-35032 Marburg, Germany

^* Author for correspondence (e-mail: stengl{at}staff.uni-marburg.de)

Accepted 6 July 2006

Pheromone-dependent mate search is under strict circadian control in different moth species. But it remains unknown whether daytime-dependent changes in pheromone sensitivity already occur at the periphery in male moths. Because adapting pheromone stimuli cause rises of cyclic guanosine monophosphate (cGMP) in pheromone-sensitive trichoid sensilla of the night-active hawkmoth Manduca sexta, we wanted to determine whether cGMP decreases pheromone-sensitivity of olfactory receptor neurons in a daytime-dependent manner. Long-term tip recordings from trichoid sensilla were performed at the early day (ZT 1-4), when many moths are still active, and at the middle of the day (ZT 8-11), when moths are resting. A non-adapting pheromone-stimulation protocol combined with perfusion of the sensillum lymph with the membrane-permeable cGMP analogue 8bcGMP adapted the action potential response but not the sensillar potential. Perfusion with 8bcGMP decreased the initial action potential frequency, decreased the numbers of action potentials elicited in the first 100 ms of the pheromone response and attenuated the reduction of action potential amplitude. Furthermore, the decrease in 8bcGMP-dependent action potential frequency was stronger in recordings made at ZT 8-11 than at ZT 1-4. In the control recordings during the course of the day the pheromone responses became increasingly tonic and less phasic. At ZT 8-11 only, this daytime-dependent effect was further enhanced by 8bcGMP application. Thus we hypothesize that during the moths' resting phase, elevated cGMP levels underlie a daytime-dependent decrease in pheromone sensitivity and a decline in the temporal resolution of pheromone pulses.

Key words: insect olfaction, pheromone transduction, moth, cyclic nucleotide, antenna, circadian difference

This article has been cited by other articles:

				J. Dolzer, S. Krannich, and M. Stengl Pharmacological Investigation of Protein Kinase C- and cGMP-Dependent Ion Channels in Cultured Olfactory Receptor Neurons of the Hawkmoth Manduca sexta Chem Senses, July 16, 2008; (2008) bjn043v1. [Abstract] [Full Text] [PDF]

				C. Merlin, P. Lucas, D. Rochat, M.-C. Francois, M. Maibeche-Coisne, and E. Jacquin-Joly An Antennal Circadian Clock and Circadian Rhythms in Peripheral Pheromone Reception in the Moth Spodoptera littoralis J Biol Rhythms, December 1, 2007; 22(6): 502 - 514. [Abstract] [PDF]