Defense reaction induced by a metabotropic glutamate receptor agonist microinjected into the dorsal periaqueductal gray of rats.
The behavioral effects of trans-(+/-)-1-amino-1, 3-cyclopentanedicarboxylic acid (t-ACPD), a metabotropic glutamate receptor (mGluR) agonist, or 0.9% (w/v) saline, injected into the dorsal periaqueductal gray (DPAG), was investigated. Male Wistar rats showed defense reactions characterized by jumps toward the top edges of the cages (saline = 0 vs t-ACPD = 6.0, medians P<0.05) and gallops (saline = 0 vs t-ACPD = 10.0, medians P<0.05) during the 60-s period after the beginning of the injection. In another experiment animals were placed inside an open arena for 5 min immediately after injection. Their behavior was recorded by a video camera and a computer program analyzed the videotapes. Eleven of fifteen rats injected with t-ACPD showed a short-lasting (about 1 min) flight reaction. No saline-treated animal showed this reaction (P<0.0005, chi-square test). The drug induced an increase in turning behavior (P = 0.002, MANOVA) and a decrease in the number of rearings (P<0.001, MANOVA) and grooming episodes (P<0.001, MANOVA). These results suggest that mGluRs play a role in the control of defense reactions in the DPAG.
Molchanov
M L
ML
Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
Guimarães
F S
FS
D000818:Animals; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003674:Defense Mechanisms; D004924:Escape Reaction / Q000187:drug effects; D008297:Male; D008845:Microinjections; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010487:Periaqueductal Gray; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists*
D018696:Neuroprotective Agents; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane