The role of group I metabotropic glutamate receptors in acquisition and expression of contextual and auditory fear conditioning in rats – a comparison

Metabotropic Glutamate 1 Receptor: Current Concepts and Perspectives

“…The novel, selective, brain-permeable, and potent mGlu1 antagonist JNJ16259685 confirmed the anxiolytic effect of mGlu1 inhibition in the Vogel test (Steckler et al, 2005). A compound structurally related to JNJ16259685, namely 3-ethyl-2-methyl-quinolin-6-yl)-(4-methoxy-cyclohexyl)-methanone methanesulfonate, although showing no activity in the elevated plus-maze test in rats, significantly inhibits fear-potentiated startle and attenuates freezing responses in the contextual fear conditioning test (Pietraszek et al, 2005;Gravius et al, 2006). In line with these findings, mGlu1-deficient mice have impairments in contextual fear conditioning (Aiba et al, 1994a).…”

“…Several studies have established the involvement of mGlu1 receptors in spatial and associative learning (Aiba et al, 1994a;Conquet et al, 1994;Nielsen et al, 1997;Steckler et al, 2005;Gravius et al, 2006). A critical role of mGlu1 receptors has been demonstrated for the acquisition of hippocampally dependent trace conditioning and for the enhancement of synaptic strength in hippocampal circuits across conditioning sessions (GilSanz et al, 2008).…”

The effects of acute treatment with escitalopram on the different stages of contextual fear conditioning are reversed by atomoxetine

“…The amygdala has an essential function in the acquisition and expression of conditioned fear to both context and cues (Ledoux 2000;Maren and Quirk 2004), whereas the hippocampus is thought to have a central role in the conditioning to context, but does not seem essential for conditioning to cues (Anagnostaras et al 2001;Knierim 2003;Maren et al 1998;Phillips and Ledoux 1992). It was reported that SSRIs reduce the conditioned freezing behavior in rats when given before the retention test (Gravius et al 2006;Hashimoto et al 1996;Inoue et al 2004), but increase this behavior when given before acquisition (Gravius et al 2006). In addition, it was shown that the acute treatment with citalopram enhances acquisition of auditory fear conditioning (Burghardt et al 2004) and enhances fear expression of tonedependent conditioned freezing (Burghardt et al 2007).…”

Effects of mGlu1 receptor blockade on working memory, time estimation, and impulsivity in rats

“…(e.g., Gravius et al 2005Gravius et al , 2006Steckler et al 2005a;Pietraszek et al 2005a;Varty et al 2005). However, similar to other glutamatergic agents, mGlu1 receptor antagonists were expected to produce side effects that had to be critically evaluated.…”