Age-dependent plasticity of sex pheromone response in the moth, Agrotis ipsilon : combined effects of octopamine and juvenile hormone
Hormones and Behavior. 2009-06-01; 56(1): 185-191
DOI: 10.1016/j.yhbeh.2009.04.005
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Male moths use sex pheromones to find their mating partners. In the moth, Agrotis
ipsilon, the behavioral response and the neuron sensitivity within the primary
olfactory centre, the antennal lobe (AL), to sex pheromone increase with age and
juvenile hormone (JH) biosynthesis. By manipulating the JH level, we previously
showed that JH controls this age-dependent neuronal plasticity, and that its
effects are slow (within 2 days). We hypothesized that the hormonal effect might
be indirect, and one neuromodulator candidate, which might serve as a mediator,
is octopamine (OA). Here, we studied the effects of OA and an OA receptor
antagonist, mianserin, on behavioral and AL neuron responses of mature and
immature males during stimulation with sex pheromone. Our results indicate that,
although OA injections enhanced the behavioral pheromone response in mature
males, OA had no significant effect on behavior in immature males. However,
mianserin injections decreased the behavioral response in mature males. AL neuron
sensitivity increased after OA treatment in immature males, and decreased after
mianserin treatment in mature males. Determination of OA levels in ALs of
immature and mature males did not reveal any difference. To study the possible
interactive effects of JH and OA, the behavioral pheromone response was analyzed
in JH-deprived mature males injected with OA, and in immature males injected with
fenoxycarb, a JH agonist, and mianserin. Results show that both JH and OA are
necessary to elicit a behavioral response of A. ipsilon males to sex pheromone.