Octopamine and tyramine modulate pheromone-sensitive olfactory sensilla of the hawkmoth Manduca sexta in a time-dependent manner

Abstract

In moths octopamine improved pheromone-dependent mate search time dependently. In the nocturnal hawkmoth Manduca sexta long-term tip recordings of trichoid sensilla were performed to investigate whether biogenic amines modulate pheromone transduction time dependently. At three Zeitgebertimes octopamine, tyramine and the octopamine antagonist epinastine were applied during non-adapting pheromone-stimulation. At ZT 8-11, during the photophase, when sensilla were adapted, octopamine and to a lesser extent tyramine increased the bombykal-dependent sensillar potential amplitude and initial action potential (AP) frequency. In addition, during the photophase, when sensilla are less able to resolve pheromone pulses, octopamine rendered pheromone responses more phasic and sensitive, and raised the spontaneous AP frequency. During the late scotophase, at ZT 22-1, when the antenna appeared maximally sensitized for pheromone pulse detection and endogenous octopamine levels are high, exogenously applied octopamine was ineffective. Epinastine blocked the pheromone-dependent AP response at ZT 8-11 and slightly affected it at ZT 22-1, while it had no effect on the sensillar potential amplitude. Epinastine decreased the spontaneous AP activity during photophase and scotophase and rendered pheromone responses more tonic in the scotophase. We hypothesize that the presence of octopamine in the antenna is obligatory for the detection of intermittent pheromone pulses at all Zeitgebertimes.

Mind the Gap: Olfactory Trace Conditioning in Honeybees

“…In insects, the US (sucrose reward) is encoded by the octopaminergic VUMmx1 neuron, which projects to the antennal lobe (Hammer, 1993). Octopamine has excitatory effects on neural activity (Flecke and Stengl, 2009). Thus, octopamine release during US presentation may reactivate the odor trace, and thus allow for coincident activity necessary for associations.…”

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

“…Injections of OA into the haemolymph enhanced the responsiveness of male moths to pheromone in behavioural experiments (Linn and Roelofs, 1986; and sensitized ORNs of different moth species during tip recordings of pheromone-sensitive trichoid sensilla (Grosmaitre et al, 2001;Pophof, 2000;Pophof, 2002). 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).…”

“…The high 8bcAMP concentration of 10 mmol l -1 used in most of the recordings was necessary to obtain significant diffusion during the first hour of the recordings and is equal to the concentration of 8-bromo 3Ј,5Ј-cyclic guanosine monophosphate employed in an earlier study (Flecke et al, 2006). In a subset of recordings the biogenic amine OA (1mmoll -1 ) was applied in the same way (Flecke and Stengl, 2009). The Ringer solutions were prepared with Hepes (all chemicals from Sigma, Deisenhofen, Germany).…”

“…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). Furthermore, ORNs of M. sexta adapt at the beginning of the photophase and respond to pheromone stimulation with lower mean action potential (AP) frequencies at the middle of the photophase (Flecke and Stengl, 2009).…”

“…The biogenic amine octopamine (OA) was shown to modulate the sensitivity of pheromone-sensitive ORNs and is thought to affect temporal encoding of pheromone pulses time dependently (Flecke and Stengl, 2009). Injections of OA into the haemolymph enhanced the responsiveness of male moths to pheromone in behavioural experiments (Linn and Roelofs, 1986; and sensitized ORNs of different moth species during tip recordings of pheromone-sensitive trichoid sensilla (Grosmaitre et al, 2001;Pophof, 2000;Pophof, 2002).…”