Effect of juvenile hormone on the central nervous processing of sex pheromone in an insect

Abstract

Behavioral sex pheromone responsiveness in the male moth Agrotis ipsilon was previously shown to be controlled by juvenile hormone (JH). However, this morphogenetic hormone did not change the sensitivity of antennae to sex pheromones. To analyze the possible involvement of JH in the central integration of the female-produced sex pheromone, we investigated the pheromone response of olfactory antennal lobe (AL) interneurons in male A. ipsilon as a function of age and JH status by using intracellular recordings. When the antennae were stimulated with the sex pheromone blend, the sensitivity of olfactory AL neurons increased with age, as does the JH-dependent behavioral and physiological development of A. ipsilon males. Furthermore, males surgically deprived of JH showed a significant decrease in the sensitivity of the AL neurons. JH injection in operated or in young males restored or induced, respectively, a high sensitivity of the AL neurons. JH seems likely to be involved in the plasticity of the adult insect brain by modulating the central nervous processing of olfactory information, thus allowing mate recognition and reproduction at the optimal time.

Figure 1

Typical response of an AL interneuron to the female sex pheromone blend in A. ipsilon. Horizontal scale bar marks the stimulation (500 ms), vertical scale bar = 10 mV.

Figure 2

Age-dependent sensitivity of AL interneurons in A. ipsilon males to the sex pheromone blend. The proportion of responding neurons with a certain threshold in males of different ages is represented in the diagrams. Day 1, 1-day-old males, n = 60 neurons. Day 3, 3-day-old males, n = 59 neurons. Day 5, 5-day-old males, n = 67 neurons.

Figure 3

Effect of JH on the sensitivity of AL interneurons in A. ipsilon males to the sex pheromone blend. The proportion of responding neurons with a certain threshold in treated males is represented in the diagrams. Males were tested 2 days after the treatment. Day 5, −CA + oil, 3-day-old allatectomized males injected with olive oil, n = 73 neurons. Day 5, −CA + JH, 3-day-old allatectomized males injected with JH, n = 70 neurons. Day 2, + JH, 0-day-old control males injected with JH, n = 69 neurons.