Neuromodulation of olfactory sensitivity in the peripheral olfactory organs of the American cockroach, Periplaneta americana.
Olfactory sensitivity exhibits daily fluctuations. Several studies have suggested that the olfactory system in insects is modulated by both biogenic amines and neuropeptides. However, molecular and neural mechanisms underlying olfactory modulation in the periphery remain unclear since neuronal circuits regulating olfactory sensitivity have not been identified. Here, we investigated the structure and function of these signaling pathways in the peripheral olfactory system of the American cockroach, Periplaneta americana, utilizing in situ hybridization, qRT-PCR, and electrophysiological approaches. We showed that tachykinin was co-localized with the octopamine receptor in antennal neurons located near the antennal nerves. In addition, the tachykinin receptor was found to be expressed in most of the olfactory receptor neurons in antennae. Functionally, the effects of direct injection of tachykinin peptides, dsRNAs of tachykinin, tachykinin receptors, and octopamine receptors provided further support for the view that both octopamine and tachykinin modulate olfactory sensitivity. Taken together, these findings demonstrated that octopamine and tachykinin in antennal neurons are olfactory regulators in the periphery. We propose here the hypothesis that octopamine released from neurons in the brain regulates the release of tachykinin from the octopamine receptor neurons in antennae, which in turn modulates the olfactory sensitivity of olfactory receptor neurons, which house tachykinin receptors.
WCU Biomodulation Major, Department of Agricultural Biotechnology, College of Agriculture & Life Sciences, Seoul, Republic of Korea.
Je Won
JW
Jung
Jin-Hee
JH
Kim
Rita
R
Pfeiffer
Young-Joon
YJ
Ahn
Terry L
TL
Page
Hyung Wook
HW
Kwon
D000818:Animals; D009655:Octopamine / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000378:metabolism; D010526:Periplaneta / Q000235:genetics / Q000378:metabolism*; D018039:Receptors, Tachykinin / Q000378:metabolism; D015320:Tachykinins / Q000378:metabolism
D018039:Receptors, Tachykinin; D015320:Tachykinins; D009655:Octopamine