Volume 17, Number 23,
Issue of December 1, 1997
pp. 9367-9374
Interaction of GABA and Excitatory Amino Acids in the Basolateral
Amygdala: Role in Cardiovascular Regulation
Received July 15, 1997; revised Sept. 2, 1997; accepted Sept. 18, 1997.
Robert P. Soltis,
Jennifer C. Cook,
Adam E. Gregg, and
Brian
J. Sanders
Departments of Pharmaceutical Sciences and Psychology, Drake
University, Des Moines, Iowa 50311
Activation of the amygdala in rats produces cardiovascular
changes that include increases in heart rate and arterial pressure as
well as behavioral changes characteristic of emotional arousal. The
objective of the present study was to examine the interaction of GABA
and excitatory amino acid (EAA) receptors in the basolateral amygdala
(BLA) in regulating cardiovascular function. Microinjection of the
GABAA receptor antagonist bicuculline methiodide (BMI) or
the E A A receptor agonists NMDA or AMPA into the same region of
the BLA of conscious rats produced dose-related increases in heart rate
and arterial pressure. Injection of the nonselective EAA receptor
antagonist kynurenic acid into the BLA prevented or reversed the
cardiovascular changes caused by local injection of BMI or the
noncompetitive GABA antagonist picrotoxin. Conversely, local
pretreatment with the glutamate reuptake inhibitor
L-trans-pyrrolidine-2,4-dicarboxylic acid
enhanced the effects of intra-amygdalar injection of BMI. The
cardiovascular effects of BMI were also attenuated by injection of
either the NMDA antagonist
3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) or the
AMPA receptor antagonist
1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX). When these two EAA receptor antagonists were combined, their
ability to suppress BMI-induced tachycardic and pressor responses was
additive. These findings indicate that the cardiovascular effects
caused by blockade of GABAergic inhibition in the BLA of the rat are
dependent on activation of local NMDA and AMPA receptors.
Key words:
basolateral amygdala;
excitatory amino acids;
NMDA;
AMPA;
bicuculline;
kynurenic acid;
L-trans-PDC;
heart
rate;
arterial pressure;
cardiovascular control