Perfusion with cAMP analogue affects pheromone-sensitive trichoid sensilla of the hawkmoth Manduca sexta in a time-dependent manner.
Octopamine causes time-dependent disadaptation of pheromone-sensitive olfactory receptor neurons (ORNs) of Manduca sexta. Because the majority of insect octopamine receptors are positively coupled to adenylyl cyclases we examined whether cyclic adenosine monophosphate (cAMP) mimics octopamine-dependent modulation of pheromone transduction in a time-dependent manner. Long-term tip recordings of single trichoid sensilla of Manduca sexta were performed during three zeitgeber times (ZTs, ZT 0=lights on), while stimulating the sensilla with two doses of the main pheromone component bombykal in a non-adapting protocol. The membrane-permeable cAMP analogue 8bcAMP increased the normalized sensillar potential amplitude in a time- and bombykal dose-dependent way. At the higher bombykal dose only, the applied 8bcAMP antagonized an endogenous decrease in the mean sensillar potential amplitude at ZT 1-4 and ZT 8-11 when ORNs were adapted but not at ZT 22-1, when ORNs were sensitized. In contrast to octopamine, 8bcAMP did not consistently affect the initial pheromone-dependent action potential frequency, the phasic/tonic response pattern, or the time-dependent shift to lower mean action potential frequencies at ZT 8-11. Furthermore, 8bcAMP increased the spontaneous action potential frequency time dependently, but differently from octopamine. In conclusion, our results show that cAMP only partly mimics the octopamine-dependent disadaptation of olfactory receptor neurons during photophase, apparently due to another missing octopamine-dependent synergistic factor such as defined intracellular calcium levels.
Biologie, Tierphysiologie, Philipps-Universität Marburg, 35032 Marburg, Germany.
Christian
C
Flecke
Andreas
A
Nolte
Monika
M
Stengl
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects / Q000528:radiation effects; D000466:Alkadienes / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D008027:Light; D008297:Male; D018402:Manduca / Q000187:drug effects* / Q000502:physiology* / Q000528:radiation effects; D009655:Octopamine / Q000494:pharmacology; D018034:Olfactory Receptor Neurons / Q000187:drug effects* / Q000502:physiology* / Q000528:radiation effects; D010477:Perfusion; D010675:Pheromones / Q000494:pharmacology*; D013997:Time Factors
D000466:Alkadienes; D010675:Pheromones; D009655:Octopamine; D015124:8-Bromo Cyclic Adenosine Monophosphate; C066482:bombykal