Effects of photoperiod on the circadian timing of pheromone response in male Trichoplusia ni: Relationship to the modulatory action of octopamine

SUMMARYIn the male moth, Agrotis ipsilon, mating induces a transient inhibition of behavioural and central nervous responses to sex pheromone. Newly mated males are not attracted to sex pheromone, and the sensitivity of their antennal lobe (AL) neurons is lower than in virgin males. This rapid transient olfactory inhibition prevents them from re-mating unsuccessfully until they have refilled their sex glands. We hypothesized that this olfactory 'switch off' might be controlled by neuromodulators such as biogenic amines. To test our hypothesis, we studied the effects of octopamine (OA) and serotonin (5-hydroxytryptamine, 5-HT) on the coding properties of pheromone-sensitive AL neurons in virgin and newly mated males. We show that AL neuron sensitivity increased in newly mated males after injection of OA or 5-HT, but only OA treatment affected certain response characteristics of AL neurons in virgin males. Whereas all measured AL neuron response characteristics were different between virgin and newly mated males, amine treatment in newly mated males restored only the latency and spike frequency, but not the duration of excitatory and inhibitory phases, which were initially found in virgin males. Additionally, we investigated the behavioural effects of OA and 5-HT treatments in virgin and mated males. Although OA and 5-HT enhanced the general flight activity of newly mated males, amine treatments did not restore the behavioural pheromone response of mated moths. Altogether, these results show that, although biogenic amines modulate the olfactory system in moths, OA and 5-HT are probably not involved in the post-mating inhibition of responses to sex pheromone in A. ipsilon males.

Section: R B Barrozo and Otherssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Mating-induced transient inhibition of responses to sex pheromone in a male moth is not mediated by octopamine or serotonin

Barrozo¹,

Jarriault²,

Simeone³

et al. 2010

“…Furthermore, the OA-cAMP affects ORNs time dependently dependent disadaptation is time dependent suggesting a circadian control of OA action (Flecke and Stengl, 2009). Consistent with this assumption is the finding that circadian changes of OA concentration in the haemolymph and brain correlate with circadian rhythms in mating behaviour (Linn et al, 1994;Linn et al, 1996;Lehman, 1990). Since most OA receptors are positively coupled to adenylyl cyclases (Evans and Maqueira, 2005;Farooqui, 2007), it is likely that the OA effects are mediated by increases in the cAMP concentration.…”

Section: Introductionmentioning

confidence: 89%

“…Also, male moths express circadian rhythms in their responsiveness to pheromone with maxima in the scotophase Linn et al, 1996;Rosén et al, 2003). For M. sexta it was shown that the maxima in calling behaviour of females (Itagaki and Conner, 1988) correlated with maximal male flight activity in the scotophase (Lingren et al, 1977;Sasaki and Riddiford, 1984).…”

Section: Introductionmentioning

confidence: 99%

Perfusion with cAMP analogue affects pheromone-sensitive trichoid sensilla of the hawkmothManduca sextain a time-dependent manner

Flecke

Nolte

Stengl

2010

SUMMARYOctopamine 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. Supplementary material available online at

“…For example, in the male silkworm moth (Antheraea polyphemus) octopamine enhances the sensitivity of neurons that detect pheromones (Pophof, 2000). This change in receptor sensitivity correlates with the increased behavioral sensitivity seen in males of several other moth species after octopamine injection (Linn and Roelofs, 1986;Linn et al, 1992Linn et al, , 1996. Male cabbage looper moths (Trichoplusia ni), for example, detect pheromones at a concentration two orders of magnitude lower than before injection of the modulator (Linn and Roelofs, 1986).…”

mentioning

confidence: 97%

Neuromodulation in invertebrate sensory systems: from biophysics to behavior

Birmingham

Tauck²

2003

SUMMARYNeuromodulation may enhance the ability of sensory circuits to respond appropriately to widely variable environmental stimuli. The functional significance of neuromodulation will emerge from understanding the effects of modulators not just on single cells and synapses, but also on networks and the behavior of intact animals. With their relatively simple circuitry and large identifiable cells, invertebrate nervous systems offer insights into the complex roles of neuromodulators in modifying networks to meet the changing needs of the animal. Here we describe the role of neuromodulation in several invertebrate sensory systems that have been studied at a variety of levels,from the biophysical up to the behavioral.