The effects of ICV-CRH on novelty-induced behavior.

To assess whether centrally administered corticotropin-releasing hormone (CRH) modulates behavioral and antinociceptive effects of exposure to a novel environment, vehicle or 0.03, 0.3, or 3.0 micrograms of CRH was administered intracerebroventricularly (ICV) to rats, which were then tested under novel or familiar conditions. Novelty decreased sleeping and grooming and increased rearing, walking, and latency to respond on the hot-plate test of analgesia. CRH increased grooming and walking, decreased rearing and sleeping, and had no effect in the hot-plate test. The lowest dose was without effect on any measure; otherwise, CRH effects generally were dose-dependent. There was no evidence that CRH selectively enhanced or interfered with novelty-induced behavioral changes; it influenced behavior to the same degree in both test conditions. However, test condition selectively modulated the degree of peptide-induced self-gnawing and burrowing.