Glutamatergic and GABAergic modulations of ultrasonic vocalizations during maternal separation distress in mouse pups.
BACKGROUND
Dysregulation of GABAergic inhibition and glutamatergic excitation has been implicated in exaggerated anxiety. Mouse pups emit distress-like ultrasonic vocalizations (USVs) when they are separated from their dam/siblings, and this behavior is reduced by benzodiazepines (BZs) which modulate GABAergic inhibition. The roles of glutamate receptors on USVs remain to be investigated.


METHODS
We examined the roles of glutamate receptor subtypes on mouse pup USVs using N-methyl-D: -aspartate (NMDA) receptor antagonists with different affinities [dizocilpine (MK-801), memantine, and neramexane] and group II metabotropic glutamate receptor agonist (LY-379268) and antagonist (LY-341495). These effects were compared with classic BZs: flunitrazepam, bromazepam, and chlordiazepoxide. To assess the role of GABA(A) receptor subunits on USVs, drugs that have preferential actions at different GABA(A)-alpha subunits (L-838417 and QH-ii-066) were tested. Seven-day-old CFW mouse pups were separated from their dam and littermates and placed individually on a 19 degrees C test platform for 4 min. Grid crossings and body rolls were measured in addition to USVs.


RESULTS
Dizocilpine dose-dependently reduced USVs, whereas memantine and neramexane showed biphasic effects and enhanced USVs at low to moderate doses. The NMDA receptor antagonists increased locomotion. LY-379268 reduced USVs but also suppressed locomotion. All BZs reduced USVs and increased motor incoordination. Neither L-838417 nor QH-ii-066 changed USVs, but both induced motor incoordination.


CONCLUSIONS
Low-affinity NMDA receptor antagonists, but not the high-affinity antagonist, enhanced mouse pup distress calls, which may be reflective of an anxiety-like state. BZs reduced USVs but also induced motor incoordination, possibly mediated by the alpha5 subunit containing GABA(A) receptors.
Takahashi
Aki
A
Department of Psychology, Tufts University, Medford, MA 02155, USA.
Yap
Jasmine J
JJ
Bohager
Dawnya Zitzman
DZ
Faccidomo
Sara
S
Clayton
Terry
T
Cook
James M
JM
Miczek
Klaus A
KA
D000818:Animals; D000831:Animals, Newborn; D014151:Anti-Anxiety Agents / Q000009:adverse effects / Q000494:pharmacology; D001007:Anxiety / Q000523:psychology*; D001522:Behavior, Animal / Q000187:drug effects; D018682:GABA Agents / Q000494:pharmacology; D008124:Locomotion / Q000187:drug effects; D008426:Maternal Deprivation; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D021122:Protein Subunits / Q000502:physiology; D011963:Receptors, GABA-A / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology*; D013018:Sound Spectrography; D014465:Ultrasonics; D014828:Vocalization, Animal / Q000187:drug effects* / Q000502:physiology
D014151:Anti-Anxiety Agents; D018682:GABA Agents; D021122:Protein Subunits; D011963:Receptors, GABA-A; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate