title: Brain GABA and glutamate levels in workers of two ant species (Hymenoptera: Formicidae): interspecific differences and effects of queen presence/absence.
abstract: Presence of amino acid neurotransmitters gamma-aminobutyric acid (GABA) and glutamate (Glu) in ant brains was reported in very few studies. To learn more about factors influencing GABA and Glu levels in ant brains, we applied high-performance liquid chromatography to measure levels of these compounds in single brains of workers of 2 ant species, Myrmica ruginodis (subfamily Myrmicinae) and Formica polyctena (subfamily Formicinae) taken from queenright/queenless colony fragments and tested in dyadic aggression tests consisting of an encounter with a nestmate, an alien conspecific or a small cricket. Brain glutamate levels were higher than those of GABA in both tested species. Brain GABA levels (in μmol/brain) and GABA : Glu ratio were higher in M. ruginodis (a submissive species) than in F. polyctena (a dominant, aggressive species) in spite of smaller brain weight of M. ruginodis. Brain glutamate levels (in μmol/brain) did not differ between the tested species, which implies that glutamate concentration (in μmol/mg of brain tissue) was higher in M. ruginodis. Queen absence was associated with increased worker brain GABA levels in F. polyctena, but not in M. ruginodis. No significant effects of opponent type were discovered. As GABA agonists enhance friendly social behavior in rodents, we hypothesize that elevated brain GABA levels of orphaned workers of F. polyctena facilitate the adoption of a new queen. This is the first report providing information on GABA and glutamate levels in single ant brains and documenting the effects of queen presence/absence on brain levels of amino acid neurotransmitters in workers of social Hymenoptera.
authors.affiliation: Laboratory of Ethology, Department of Neurophysiology, Nencki Institute of Experimental Biology PAS, Warsaw; Department of Pharmacology and Physiology of the Nervous System, Institute of Psychiatry and Neurology, Warsaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wnuk
authors.forename: Wojciech
authors.initials: W
authors.lastname: Kostowski
authors.forename: Julita
authors.initials: J
authors.lastname: Korczyńska
authors.forename: Anna
authors.initials: A
authors.lastname: Szczuka
authors.forename: Beata
authors.initials: B
authors.lastname: Symonowicz
authors.forename: Przemysław
authors.initials: P
authors.lastname: Bieńkowski
authors.forename: Paweł
authors.initials: P
authors.lastname: Mierzejewski
authors.forename: Ewa Joanna
authors.initials: EJ
authors.lastname: Godzińska
mesh_terms: D000374:Aggression; D000818:Animals; D001000:Ants / Q000502:physiology*; D001921:Brain / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D018698:Glutamic Acid / Q000378:metabolism*; D015398:Signal Transduction; D012919:Social Behavior; D013045:Species Specificity; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid
keywords: Formica polyctena; GABA; Myrmica ruginodis; glutamate; interspecific differences; queen