Cold water swim stress increases the expression of neurotensin mRNA in thelateral hypothalamus and medial preoptic regions of the rat brain

Stress-induced analgesia is a well-documented phenomenon that occurs in all mammalian species. Forced cold water swim produces a type of stress-induce d analgesia that is independent of mu opioid receptors. The neuropeptide ne urotensin (NT) has been implicated in mu opioid-independent analgesia (MOIA ), but the circuitry of this system is largely unknown. The medial preoptic area (MPO) and lateral hypothalamus (LH) are two regions that are known to modulate pain processing. These two regions also contain neurotensinergic projections to the periaqueductal gray, a region that has been shown to pro duce MOIA upon injection of NT. The goal of this study was to determine if cold water swim (CWS) stress, which produces MOIA, activates the NT-ergic s ystems in these two regions. In situ hybridization results indicate that CW S increases the level of NT mRNA within neurons in the MPO and LH, suggesti ng that these two regions are activated during this process. (C) 2001 Elsev ier Science B.V. All rights reserved.