No evidence that post-training dopamine D2 receptor agonism affects fear generalization in male rats.

backgroundThe neurotransmitter dopamine plays an important role in the processing of emotional memories, and prior research suggests that dopaminergic manipulations immediately after fear learning can affect the retention and generalization of acquired fear.

aimsThe current study focuses specifically on the role of dopamine D2 receptors (D2Rs) regarding fear generalization in adult, male Wistar rats, and aims to replicate previous findings in mice.

methodsIn a series of five experiments, D2R (ant)agonists were injected systemically, immediately after differential cued fear conditioning (CS+ followed by shock, CS- without shock). All five experiments involved the administration of the D2R agonist quinpirole at different doses versus saline (

resultsWe found no indications for an effect of quinpirole or raclopride on fear generalization during this drug-free test. Importantly, and contradicting earlier research in mice, the evidence for the absence of an effect of D2R agonist quinpirole (1 mg/kg) on fear generalization was substantial according to Bayesian analyses and was observed in a highly powered experiment (

conclusionIn contrast with prior studies in mice, we have obtained evidence against a preventative effect of post-training D2R agonist quinpirole administration on subsequent fear generalization in rats.