Release of glutamate and GABA in the amygdala of conscious rats by acute stress and baroreceptor activation: differences between SHR and WKY rats.
To reveal the functional importance of amino acid neurotransmission in the amygdala (AMY) of conscious spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, the in vivo release of glutamate (GLU) and GABA in this brain structure was studied using the push-pull superfusion technique. Basal GLU and GABA release rates in the AMY were comparable in SHR and WKY rats, although arterial blood pressure (BP) in SHR (152+/-6 mmHg) was higher than in WKY rats (102+/-4 mmHg). Neuronal depolarization by superfusion with veratridine enhanced the release of GLU and GABA to a similar extent in both rat strains. On the other hand, exposure to noise stress (95 dB) for 3 min led to a tetrodotoxin-sensitive increase in GLU release in the AMY of SHR, but not WKY rats. The concurrent pressor response to noise was enhanced in SHR as compared to WKY rats. A rise in BP induced by intravenous infusion of phenylephrine for 9 min had no effect on amino acid release in the AMY of both strains. The data suggest an exaggerated stress response of glutamatergic neurons in the AMY of SHR as compared with WKY rats, which might be of significance for the strain differences in the cardiovascular and behavioural responses to stress. The results also show that, in both rat strains, glutamatergic and GABAergic neurons in the AMY are not modulated by baroreceptor activation. Moreover, hypertension in adult SHR does not seem to be linked to a disturbed synaptic regulation of glutamatergic or GABAergic transmission in the AMY.
Singewald
N
N
Department of Pharmacology and Toxicology, University of Innsbruck, Peter-Mayr-Strasse 1, A-6020, Innsbruck, Austria. nicolas.singewald@uibk.ac.at
Kouvelas
D
D
Mostafa
A
A
Sinner
C
C
Philippu
A
A
D000679:Amygdala / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D003243:Consciousness / Q000187:drug effects* / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011311:Pressoreceptors / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013312:Stress, Physiological / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D014701:Veratridine