title: Exposure to exogenous enkephalins disrupts reproductive development in the Eastern lubber grasshopper, Romalea microptera (Insecta: Orthoptera).
abstract: Enkephalins play a major role in reproductive physiology in crustaceans; however their role in reproductive development in insects is largely unknown. We investigated the effect of exposure to exogenous leucine-enkephalin (Leu-Enk), methionine-enkephalin (Met-Enk), and the opioid antagonist naloxone on gonad development in the Eastern lubber grasshopper, Romalea microptera. Injection of either Leu-Enk or naloxone alone significantly increased the testicular index and testicular follicular diameter in males, and the ovarian index, oocyte length, and oocyte diameter in females. In contrast, injection of Met-Enk inhibited all measures of reproductive development in both sexes. Surprisingly, co-injection of naloxone with either enkephalin enhanced the effect associated with administration of the enkephalin alone. This study clearly demonstrates the ability of enkephalins to disrupt insect sexual development and also suggests the existence of conserved enkephaline-dependent regulatory mechanisms in insects and crustaceans.
authors.affiliation: Department of Biology, University of Central Florida, Orlando, FL, USA. skumar@knights.ucf.edu
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kumar
authors.forename: Ganji Purnachandra
authors.initials: GP
authors.lastname: Nagaraju
authors.forename: Purnachandra Nagaraju
authors.initials: PN
authors.lastname: Ganji
authors.forename: Hojun
authors.initials: H
authors.lastname: Song
authors.forename: Laurence
authors.initials: L
authors.lastname: von Kalm
authors.forename: David W
authors.initials: DW
authors.lastname: Borst
mesh_terms: D000818:Animals; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology*; D005260:Female; D006110:Grasshoppers / Q000187:drug effects* / Q000254:growth & development*; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects; D010053:Ovary / Q000187:drug effects / Q000254:growth & development; D012098:Reproduction / Q000187:drug effects; D013737:Testis / Q000187:drug effects / Q000254:growth & development
chemical_list: D004745:Enkephalins; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine