Effects of CRF on Spontaneous and Sensory-Evoked Activity of Locus Coeruleus Neurons
The isolation and characterization of corticotropin-releasing factor (CRF), while relatively recent, has generated a vast literature describing aspects of CRF localization, behavioral effects, autonomic effects, endocrine effects, and cellular mechanisms for adrenocorticotropic hormone release. Preliminary findings suggest that increased spontaneous discharge rate of locus coeruleus (LC) neurons is a direct effect of CRF. The unanesthetized rat is a better preparation in which to study CRF effects on LC sensory-evoked activity because LC neurons are responsive to multimodal nonnoxious stimuli in the unanesthetized state. The mechanism by which CRF alters LC activity is merely speculative since such studies are lacking. The finding that CRF increases LC spontaneous discharge as do stressful stimuli suggest that these particular stimuli produce their electrophysiological effects by releasing CRF from fibers localized within the LC. The importance of CRF activation of LC discharge is determined by the influence of LC discharge on its diverse target cells.