title: GABA and GAD expression in the X-organ sinus gland system of the Procambarus clarkii crayfish: inhibition mediated by GABA between X-organ neurons.
abstract: In crustaceans, the X-organ-sinus gland (XO-SG) neurosecretory system is formed of distinct populations of neurons that produce two families of neuropeptides: crustacean hyperglycemic hormone and adipokinetic hormone/red pigment-concentrating hormone. On the basis of electrophysiological evidence, it has been proposed that γ-aminobutyric acid (GABA) regulates both electrical and secretory activity of the XO-SG system. In this work we observed that depolarizing current pulses to neurons located in the external rim of the X-organ induced repetitive firing that suppressed the spontaneous firing of previously active X-organ neurons. Picrotoxin reversibly blocked this inhibitory effect suggesting that the GABA released from the stimulated neuron inhibited neighboring cells. Immunoperoxidase in X-organ serial sections showed co-localization of GABA and glutamic acid decarboxylase (GAD) including the aforementioned neurons. Immunofluorescence in whole mount preparations showed that two subpopulations of crustacean hyperglycemic hormone-containing neurons colocalized with GABA. The expression of GAD mRNA was determined in crayfish tissue and X-organ single cells by RT-PCR. Bioinformatics analysis shows, within the amplified region, 90.4% consensus and 41.9% identity at the amino acid level compared with Drosophila melanogaster and Caenorhabditis elegans. We suggest that crustacean hyperglycemic hormone-GABA-containing neurons can regulate the excitability of other X-organ neurons that produce different neurohormones.
authors.affiliation: Department of Physiology, Biophysics and Neurosciences, CINVESTAV-IPN, Mexico City, Mexico.
authors.forename: Paola
authors.initials: P
authors.lastname: Pérez-Polanco
authors.forename: Julieta
authors.initials: J
authors.lastname: Garduño
authors.forename: Jorge
authors.initials: J
authors.lastname: Cebada
authors.forename: Natanael
authors.initials: N
authors.lastname: Zarco
authors.forename: José
authors.initials: J
authors.lastname: Segovia
authors.forename: Mónica
authors.initials: M
authors.lastname: Lamas
authors.forename: Ubaldo
authors.initials: U
authors.lastname: García
mesh_terms: D000818:Animals; D060829:Arthropod Proteins / Q000096:biosynthesis / Q000378:metabolism; D003400:Astacoidea / Q000502:physiology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D007447:Invertebrate Hormones / Q000096:biosynthesis / Q000378:metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009489:Neurosecretion / Q000187:drug effects / Q000502:physiology; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D061251:Primary Cell Culture; D011817:Rabbits; D051381:Rats; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*
chemical_list: D060829:Arthropod Proteins; D007447:Invertebrate Hormones; D009419:Nerve Tissue Proteins; C015947:hyperglycemic hormone, crustacean; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase