Defense reaction induced by a metabotropic glutamate receptor agonist microinjected into the dorsal periaqueductal gray of rats

Abstract

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.

Role of nitric oxide in the periaqueductal gray in defensive behavior in mice: influence of prior local N-methyl-D-aspartate receptor activation and aversive condition

“…The excitatory amino acid induced a sudden sequence of jumping and running behaviors that were followed by a period of freezing. These results corroborate many previous studies (Bandler, 1988;Bandler & Carrive, 1988;Beckett et al, 1992;De Oliveira et al, 2001;Molchanov & Guimaraes, 1999), which demonstrated that intra-PAG injections of glutamate receptor agonists produce defensive reactions in rodents. NPLA antagonized these NMDA-induced behavioral effects, suggesting that NO release within the PAG plays a role in defensive behavior.…”

Role of nitric oxide in the periaqueductal gray in defensive behavior in mice: Influence of prior local N-methyl-D-aspartate receptor activation and aversive condition.

“…The excitatory amino acid induced a sudden sequence of jumping and running behaviors that were followed by a period of freezing. These results corroborate many previous studies (Bandler, 1988;Bandler & Carrive, 1988;Beckett et al, 1992;De Oliveira et al, 2001;Molchanov & Guimaraes, 1999), which demonstrated that intra-PAG injections of glutamate receptor agonists produce defensive reactions in rodents. NPLA antagonized these NMDA-induced behavioral effects, suggesting that NO release within the PAG plays a role in defensive behavior.…”

Effects of intra-infralimbic prefrontal cortex injections of cannabidiol in the modulation of emotional behaviors in rats: Contribution of 5HT1A receptors and stressful experiences

“…This inactivation would lead to reduction in the activation of glutamatergic projections from IL to encephalic regions associated with anxiety such as the dorsolateral periaqueductal gray (dlPAG). Electrical and chemical stimulation of this region causes defensive responses [68,69,70] whereas its inhibition induces anxiolytic effects [71][72][73][74][75]. Therefore, intra-IL CBD could lead, depending on the animal model used, to preferential activation/inactivation of different structures such as the amygdala in CFC and the dlPAG in the EPM.…”