Stimulation of cyclic AMP formation and nerve electrical activity by octopamine in the terminal abdominal ganglion of the female gypsy moth Lymantria dispar.
The biogenic amine octopamine is known to be present in the abdominal ganglia of some insects, but the expression of functional octopamine receptors in these neuronal structures has not yet been characterized. In the present study, we describe the presence in the female gypsy moth terminal abdominal ganglion (TAG), a key structure in the control of the insect reproductive behavior, of an octopamine receptor coupled to stimulation of adenylyl cyclase through the GTP-binding protein G(s). The rank order of potency of different antagonists, which discriminate between the different classes of octopamine receptors, indicated the involvement of the neuronal type 3 receptor. The octopamine-stimulated adenylyl cyclase activity was inhibited by Ca(2+) in the low micromolar range and by activation of either protein kinase A or protein kinase C. In the isolated TAG, bath application of octopamine caused an increase of the spontaneous bursting activity of the emerging nerve of the 5th pair (V), whereas the antagonist mianserin reduced the nerve spiking activity and blocked the stimulatory effect of octopamine. These data demonstrate that the gypsy moth TAG expresses functional octopamine receptors, which may participate in the neuronal control of the insect reproductive behavior.