GABA selectively controls the secretory activity of oxytocin neurons in the rat supraoptic nucleus.
Recently we reported that a single social defeat experience triggers the release of oxytocin (OXT) from somata and dendrites, but not axon terminals, of neurons of the hypothalamic-neurohypophysial system. To further investigate the regulatory mechanisms underlying this dissociated release, we exposed male Wistar rats to a 30-min social defeat and monitored release of the inhibitory amino acids gamma amino butyric acid (GABA) and taurine within the hypothalamic supraoptic nucleus (SON) using microdialysis. Social defeat caused a significant increase in the release of both GABA and taurine within the SON (up to 480%; P < 0.01 vs. prestress release). To reveal the physiological significance of centrally released GABA, the specific GABAA-receptor antagonist bicuculline (0.02 mm) was administered into the SON via retrodialysis. This approach caused a significant increase in the release of OXT both within the SON and into the blood under basal conditions and during stress (up to 300 and 200%, respectively; P < 0.05 vs. basal values), without affecting plasma vasopressin. Electrophysiological studies confirmed the selective action of bicuculline on the firing activity of OXT neurons in the SON. Taken together, our data demonstrate that GABA is released within the SON during emotional stress to act as a selective inhibitor of both central and peripheral OXT secretion.
Otto-von-Guericke-Universität Magdeburg, Institut für Medizinische Neurobiologie, Leipziger Str. 44, D-39120 Magdeburg, Germany. mario.engelmann@medizin.uni-magdeburg.de
Mario
M
Engelmann
Philip M
PM
Bull
Colin H
CH
Brown
Rainer
R
Landgraf
Thomas F W
TF
Horn
Nicolas
N
Singewald
Mike
M
Ludwig
Carsten T
CT
Wotjak
D000200:Action Potentials / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001640:Bicuculline / Q000494:pharmacology; D002766:Cholecystokinin; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004333:Drug Administration Routes; D004594:Electrophysiology / Q000379:methods; D005470:Fluorometry / Q000379:methods; D018756:GABA Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis / Q000379:methods; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000378:metabolism; D013495:Supraoptic Nucleus / Q000166:cytology* / Q000187:drug effects; D013654:Taurine / Q000378:metabolism; D014667:Vasopressins / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018756:GABA Antagonists; D014667:Vasopressins; D013654:Taurine; D018698:Glutamic Acid; D010121:Oxytocin; D005680:gamma-Aminobutyric Acid; D002766:Cholecystokinin; D001640:Bicuculline