Effects of infusion of corticotropin-releasing factor antagonist into the locus coeruleus on freezing behavior and brain catecholamines in rats

Administration of 0.2 μg of alpha-helical CRF9-41 (corticotropin-releasing factor receptor antagonist, ahCRF9-41) into the locus coeruleus (LC) region significantly reduced footshock-induced freezing behavior in adult male rats. Changes in the concentrations of noradrenaline (NA), dopamine and their catabolites in cortex, hippocampus and hypothalamus of footshocked rats were reminiscent of those observed in stressed animals. Rats injected with ahCRF prior to footshock displayed cerebral catecholamine responses that were not different from controls injected with vehicle. The results confirm earlier findings that CRF receptors at the LC region may mediate freezing and behavioral expression of fear. However, the results also suggest that though CRF receptors within the LC region mediate footshock-induced behavior, they are not necessarily involved in the short-term catecholamine response to footshock.