Role of corticotropin-releasing factor and urocortin within the basolateral amygdala of rats in anxiety and panic responses

The amygdala is a critical temporal lobe structure involved in the expression of anxiety and stress responses. The basolateral nucleus (BLA) of the amygdala in particular, may play a key role in anxiety. Furthermore, corticotropin-releasing factor (CRF), a 41 amino acid peptide, has been strongly implicated in the regulation of stress and anxiety responses. Centrally administered CRF has been shown to increase the anxiety-like behaviors of rodents in several animal models. A recently cloned related peptide, Urocortin (Ucn), appears to have similar affinity for the CRF 1 receptor, but higher affinity at the CRF 2 receptor. When microinjected into the BLA, we found Ucn was substantially more potent than CRF in producing anxiogenic-like behavior as assessed in the social interaction test. Furthermore, repetitive administration of subthreshold doses of Ucn and CRF resulted in `priming'. Once primed, these animals exhibited behavioral and cardiovascular responses to intravenous sodium lactate, a panicogenic agent in susceptible human patients. These results suggest central CRF and Ucn play a role in generating anxiety which may be similar to that seen in pathological conditions such as panic disorder.