Neural regulation of sex-pheromone glands in Lepidoptera

Abstract

Substantial progress has been made toward understanding the neuroendocrine regulation of sexpheromone glands in Lepidoptera, but several recent studies have revealed that direct contact of the pheromone gland with blood-borne factors is not necessary to induce pheromone biosynthesis and release in some species. The nervous system provides an alternate route of activanon. Evidence from several species indicates that the pheromone gland IS innervated and regulated by neural activity. Electrical stimulation of efferent axons arising from the terminal abdominal ganglion results in a significant increase in pheromone production, and neural stimulation furthermore evokes the rapid release of pheromone taro the surrounding air. In some heliothine moths, the biogemc monoamine octopamme stimulates pheromone production, and octopamine has also been isolated from pheromone gland tissue. Moreover. the critical period for maximal ocropamine action mirrors the time when peak levels of octopamme are present tn the gland. These findings suggest that octopamine is involved in the regulation of pheromone biosvnthesis and/or release but its acnons depend on additional factors associated with age and photoperiod. The combined evidence using anatomical, electrophysiological, and biochemical methods indicates that the pheromone gland is innervated and regulfited by neurons that arise in the terminal abdominal ganglion. Indirect evidence suggests that at least some of this mnervanon is ocropammergic. In these respects, the pheromone gland in Lepidoptera exhibits characteristics of other neuroeffector systems m insects.

Neuroendocrine control of pheromone production in moths

“…It has been proposed, however, that the innervation of the pheromone gland is crucial for pheromonotropic activity and that the biogenic amine, octopamine, may be involved as an intermediate messenger during the stimulation of sex pheromone production in Lepidoptera (Christensen et al, 1991(Christensen et al, , 1992Christensen and Hildebrand, 1995). Ventral nerve cord (VNC) stimulation and injections of octopamine to mid-photophase females resulted in the stimulation of pheromone biosynthesis (Christensen et al, 1991).…”

Neuroanatomy and immunocytochemistry of the median neuroendocrine cells of the subesophageal ganglion of the tobacco hawkmoth,Manduca sexta: Immunoreactivities to PBAN, and other neuropeptides

“…Hormonal regulation of the sex-pheromone gland of M. sextu does not preclude the possibility that the gland is also regulated, in part, by a descending neural pathway. The evidence for neural regulation of the sexpheromone gland of moths has been reviewed by Christensen and Hildebrand (1995), and these authors report that bath application of PBAN to the terminal abdominal ganglion of M. sextu results in activation of certain efferent cells of this ganglion. Moreover, Thyagaraja and Raina (1994) have shown that in L. dispar, severance of the ventral nerve cord blocks pheromone production and application of PBAN to the severed terminal abdominal ganglion results in significant pheromone production.…”

“…There remain uncertainties regarding the role of PBAN in the control of the pheromone gland of female Lepidoptera (Christensen and Hildebrand, 1995). In addition, PBAN is known to occur in larvae and in adult male Lepidoptera, but its function in these insects is unknown.…”

The pheromonal gland of Lymantria dispar: Morphology and evidence for its innervation

“…This assumption has been corroborated by subsequent work (Hollander and Yin, 1985;Tang et al, 1987;Thyagaraja and Raina, 1994) and a neuronal input descending from the brain/subesophageal ganglion and intact connections all the way to the TAG seem required in the regulation of the gypsy moth pheromone production (Thyagaraja and Raina, 1994). Evidence from several moth species indicates that the pheromone gland is innervated and regulated by TAG neurons and that neural stimulation from the TAG significantly increases the pheromone production and dispersal (see Christensen et al, 1991;Christensen and Hildebrand, 1995). Interestingly, the biogenic monoamine octopamine appears involved in this process in some moths (Christensen et al, 1991(Christensen et al, , 1992Christensen and Hildebrand, 1995).…”

“…Evidence from several moth species indicates that the pheromone gland is innervated and regulated by TAG neurons and that neural stimulation from the TAG significantly increases the pheromone production and dispersal (see Christensen et al, 1991;Christensen and Hildebrand, 1995). Interestingly, the biogenic monoamine octopamine appears involved in this process in some moths (Christensen et al, 1991(Christensen et al, , 1992Christensen and Hildebrand, 1995). We have detected octopamine-like immunoreactive neurons in the L. dispar TAG, as well as colocalization of octopamine-like immunoractive material and the retrogradely transported tracer tetramethylrhodamineconiugated dextran amine (TMR-DA) in a number of TAG neurons TMR-DA backfilled via the 4th-6th TAG nerves (Boi et al, 2006).…”