[Ventrolateral periaqueductal gray metabotropic glutamate receptor subtypes 7 and 8 mediate opposite effects on cardiosomatic motor reflex in rats].
OBJECTIVE
To investigate the role of ventrolateral periaqueductal gray (VL-PAG) metabotropic glutamate receptors subtype 7 and 8 (mGluR 7/8) in descending modulation of cardiosomatic motor reflex (CMR) in rats.


METHODS
AMN082 (agonist of mGluR 7) and DCPG (agonist of mGluR 8) were injected into the VL-PAG of a rat model of CMR to observe their effects in modulating CMR. The raphe magnus nucleus (NRM) or the gigantocellular reticular nucleus (Gi) was then damaged, and the changes in VL-PAG descending modulation were observed.


RESULTS
Selective activation of mGluR 7 of the VL-PAG by AMN082 obviously facilitated capsaicin (CAP)-induced CMR (P<0.05), which was suppressed by DCPG-induced mGluR 8 activation (P<0.05). These facilitatory or inhibitory effects were completely reversed by group III mGluR antagonist MSOP. Damaging the NRM of VL-PAG main relay nucleus did not significantly affect the facilitatory effect produced by AMN082 microinjection (P>0.05), but partially attenuated the inhibitory effect of DCPG microinjection (P<0.05). Both the facilitatory effect of AMN082 and the inhibitory effect of DCPG were reduced obviously after bilateral Gi damage (P<0.05).


CONCLUSIONS
VL-PAG mGluR 7 and mGluR 8 mediate biphasic regulation of CMR in rats probably through activation of different sub-nuclei and different neurons in the rostroventral medulla.
Department of Basic Medicine, Xi'an Medical University, Xi'an 710021, China. E-mail: suna1935@139.com.
Na
N
Sun
Lingheng
L
Kong
Ligang
L
Niu
Juanxia
J
Zhu
Yan
Y
Xu
Jianqing
J
Du
D000818:Animals; D001559:Benzhydryl Compounds / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D010487:Periaqueductal Gray / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000378:metabolism; D012018:Reflex / Q000502:physiology*
D001559:Benzhydryl Compounds; D001565:Benzoates; C507346:N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride; D018094:Receptors, Metabotropic Glutamate; C102719:metabotropic glutamate receptor 7; C111435:metabotropic glutamate receptor 8; D005998:Glycine