POSTER PRESENTATION ABSTRACTS
Please note: All posters will be displayed in
Salons 10-12.
FRIDAY, 10:15-11:00 AM
Fu LW, Zhou W, Guo ZL, Tjen-A-Looi S, Li P, Longhurst,
J.
Role of glutamate in rVLM in electroacupuncture-modulated
visceral sympathoexcitatory reflexes.
Susan Samueli Center of Integrative Medicine,
Department of Medicine, College of Medicine, University of California,
Irvine lwfu@uci.edu
PROCEDURE: Previous studies from our laboratory
and others have shown that neurons in the rostral ventral lateral medulla
(rVLM) receive convergent input from visceral organs and somatic nerves
during electroacupuncture (EA) and that glutamate (Glu) is an important
excitatory neurotransmitter in the rVLM. Therefore, we hypothesized
that Glu in the rVLM plays an important role in EA-modulated visceral
sympathoexcitatory reflexes.
METHODS: Experiments were conducted in anesthetized
cats. Neuronal responses to iontophoresis of glutamate into the rVLM
with and without EA were evaluated by using extracellular neural recording
techniques. Cardiovascular excitatory blood pressure responses were
evoked by application of BK on the gallbladder with and without EA.
Glu concentrations [Glu] were measured by HPLC from samples collected
by microdialysis probes inserted bilaterally into the rVLM. The BK-activated
neurons in the rVLM and the relationship to opioid system were identified
by a fluorescent immunohistochemical labeling technique.
RESULTS: We observed that iontophoresis of glutamate
into the rVLM increased neuronal activity of premotor sympathetic cardiovascular
neurons and EA decreased the neuronal responses to Glu. Repeated application
of BK (5-10 _g) on the gallbladder every 30 min increased mean arterial
pressure (MAP) and [Glu] by 31±6 mmHg and 0.13±0.03 _M respectively
(n=7) and these responses to BK stimulation were repeatable. The BK-induced
Glu release in the rVLM was not altered by barodenervation (n=5). The
BK-induced increase in [Glu] was attenuated by 70% following 30 min
of EA at P 5-6 acupoints over the median nerve (n=7). Thirty min of
EA alone at the P 5-6 acupoints caused a small increase in [Glu] in
the rVLM (n=5, P>0.05). Microdialysis of naloxone (100 mM) into the
rVLM reversed acupuncture-related inhibition (n=3). Immunohistochemical
evidence showed that neurons double-labeled with c-Fos and the vesicular
glutamate transports, VGLUT3, in the rVLM were increased following BK
stimulation. Moreover the activated neurons contain opioid delta receptors.
CONCLUSION: These preliminary data suggest that
EA through the delta receptors on glutamatergic neurons in the rVLM
modulates visceral sympathoexcitatory reflex. Supported in part by HL72125
and HL 63313.
Back