Archival ReportInfralimbic D2 Receptors Are Necessary for Fear Extinction and Extinction-Related Tone Responses
Section snippets
Subjects
Male Sprague-Dawley rats (270–320 g) were obtained, housed, and handled as described previously (20). Rats were restricted to 18 g of standard laboratory rat chow daily and were subsequently trained to bar press for food pellets on a variable interval schedule (VI 60 sec). Throughout behavioral experiments, rats were able to press for food to maintain a constant level of activity against which freezing could be reliably measured (20). All procedures were approved by the Institutional Animal
Systemic Blockade of Dopaminergic D2 Receptors Impairs Consolidation of Extinction Memory
We first examined whether dopamine, acting at D2 receptors, is necessary for extinction learning. Rats were fear conditioned on day 1 and were systemically injected with the D2 receptor antagonist raclopride (.3 mg/kg IP) or saline 10 min before extinction training on day 2. Rats injected with raclopride expressed significantly higher levels of freezing on average than rats injected with saline throughout the extinction session (Figure 1A). Analysis of variance revealed a main effect of group [F
Discussion
The present study demonstrates that D2 receptor signaling is necessary for extinction of conditioned fear. Blockade of D2 receptors in IL during fear extinction impairs later retrieval of extinction, implicating D2 receptor signaling in this structure. Although raclopride did not affect firing rate or bursting in IL, it attenuated extinction-related tone responses. Thus, D2 receptor signaling in IL promotes fear extinction, presumably by enabling tone responses during extinction that are
References (45)
- et al.
A role for dopamine D2 receptors in reversal learning
Neuroscience
(2009) - et al.
Brain mechanisms of fear extinction: Historical perspectives on the contribution of prefrontal cortex
Biol Psychiatry
(2006) The projections of the ventral tegmental area and adjacent regions: A combined fluorescent retrograde tracer and immunofluorescence study in the rat
Brain Res Bull
(1982)- et al.
Predicting how equipotent doses of chlorpromazine, haloperidol, sulpiride, raclopride and clozapine reduce locomotor activity in mice
Eur Neuropsychopharmacol
(2000) - et al.
Consolidation of fear extinction requires NMDA receptor-dependent bursting in the ventromedial prefrontal cortex
Neuron
(2007) - et al.
Inhibition of amygdaloid dopamine D2 receptors impairs emotional learning measured with fear-potentiated startle
Brain Res
(2001) - et al.
Atropine acts in the ventral striatum to reduce raclopride-induced catalepsy
Eur J Pharmacol
(2001) - et al.
D1- and D2-receptor antagonists induce catalepsy via different efferent striatal pathways [corrected]
Neurosci Lett
(1988) - et al.
Acute systemic blockade of D2 receptors does not accelerate the extinction of cocaine-associated place preference
Brain Res
(2009) - et al.
An Akt/beta-arrestin 2/PP2A signaling complex mediates dopaminergic neurotransmission and behavior
Cell
(2005)