Ethanol concentration-dependent effects and the role of stress on ethanol drinking in corticotropin-releasing factor type 1 and double type 1 and 2 receptor knockout mice.

RATIONALE: Exposure to stressors promotes ethanol (EtOH) consumption and enhances drug craving during abstinence. Corticotropin-releasing factor (CRF), and in particular, CRF actions via type 1 CRF receptors (CRF(1)) are critical in behavioral responses to stressors. CRF(1) play a role in EtOH-induced behavioral neuroadaptation, in binge-like EtOH consumption, and in heightened EtOH consumption in dependent animals. OBJECTIVES: We investigated the involvement of CRF(1) in swim-stress-induced changes in EtOH consumption and in baseline consumption as a function of EtOH concentration. The role of CRF(2) in adapting to effects of the stressor was also examined. METHODS: Wild-type mice and knockout mice lacking CRF(1) were tested for two-bottle choice EtOH consumption at concentrations of 3-20%. Also, intake of 10% EtOH was examined in wild-type mice and knockout mice lacking CRF(1), or lacking both CRF(1) and CRF(2), before and after acute or repeated swim stress exposures. RESULTS: EtOH intake was reduced in CRF(1) compared with wild-type mice when presented at a concentration of 20% but not when presented at lower concentrations. No genotype-dependent effects were found for saccharin or quinine drinking. Acute swim stress had no effect, but repeated swim stress resulted in higher levels of EtOH consumption in wild-type mice, compared with both types of knockout mice. Stress effects on EtOH drinking were longer lasting in double knockout mice. CONCLUSIONS: These data suggest a prominent role of CRF(1) in stressor-induced changes in EtOH consumption, with involvement of CRF(2) in recovery from stressor effects.

A comparison of the physiological exercise intensity differences between shod and barefoot submaximal deep-water running at the same cadence.

The purpose of this investigation was to identify whether physiological exercise intensity differed with the use of aquatic training shoes (ATS) during deep-water running (DWR) compared to using a barefoot condition. Eight male intercollegiate (National Collegiate Athletic Association Division III [NCAA III]) varsity distance runners were videotaped from the right sagittal view while running on a treadmill (TR) and while barefoot in deep water at 60-70% of their TR VO2max for 30 minutes. Based on the stride rate of the barefoot DWR trial, a subsequent 30-minute session was completed while wearing ATS. Variables of interest were energy expenditure, oxygen consumption (VO2), heart rate, respiratory exchange ratio (RER), and rating of perceived exertion (RPE). Multivariate omnibus tests revealed statistically significant differences for energy expenditure (p < 0.011), VO2 (p < 0.001), RPE (p < 0.001), and RER (p < 0.002). The post hoc pairwise comparisons revealed significant differences between barefoot and shod DWR conditions for energy expenditure (p < 0.005) and VO2 (p < 0.002), representing a 9 and 7.6% increase in exercise intensity demand while running shod vs. barefoot. These comparisons also revealed significantly higher RPE and RER values while DWR than those found in TR. Wearing the ATS may be recommended as a method of statistically significantly increasing the exercise intensity while running in deep water as compared to not wearing a shoe. Shod compared to TR yields very small differences, which indicates that the shoes may help better match land-based running exercise intensities.

Corticotropin-releasing factor-1 receptor involvement in behavioral neuroadaptation to ethanol: a urocortin1-independent mechanism.

A common expression of neuroadaptations induced by repeated exposure to addictive drugs is a persistent sensitized behavioral response to their stimulant properties. Neuroplasticity underlying drug-induced sensitization has been proposed to explain compulsive drug pursuit and consumption characteristic of addiction. The hypothalamic-pituitary-adrenal (HPA) axis-activating neuropeptide, corticotropin-releasing factor (CRF), may be the keystone in drug-induced neuroadaptation. Corticosterone-activated glucocorticoid receptors (GRs) mediate the development of sensitization to ethanol (EtOH), implicating the HPA axis in this process. EtOH-induced increases in corticosterone require CRF activation of CRF1 receptors. We posited that CRF1 signaling pathways are crucial for EtOH-induced sensitization. We demonstrate that mice lacking CRF1 receptors do not show psychomotor sensitization to EtOH, a phenomenon that was also absent in CRF1 + 2 receptor double-knockout mice. Deletion of CRF2 receptors alone did not prevent sensitization. A blunted endocrine response to EtOH was found only in the genotypes showing no sensitization. The CRF1 receptor antagonist CP-154,526 attenuated the acquisition and prevented the expression of EtOH-induced psychomotor sensitization. Because CRF1 receptors are also activated by urocortin-1 (Ucn1), we tested Ucn1 knockout mice for EtOH sensitization and found normal sensitization in this genotype. Finally, we show that the GR antagonist mifepristone does not block the expression of EtOH sensitization. CRF and CRF1 receptors, therefore, are involved in the neurobiological adaptations that underlie the development and expression of psychomotor sensitization to EtOH. A CRF/CRF1-mediated mechanism involving the HPA axis is proposed for acquisition, whereas an extrahypothalamic CRF/CRF1 participation is suggested for expression of sensitization to EtOH.

Endotoxin preconditioning protects against the cytotoxic effects of TNFalpha after stroke: a novel role for TNFalpha in LPS-ischemic tolerance.

Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury. Tumor necrosis factor-alpha (TNFalpha) is protective in LPS-induced preconditioning yet exacerbates neuronal injury in ischemia. Here, we define dual roles of TNFalpha in LPS-induced ischemic tolerance in a murine model of stroke and in primary neuronal cultures in vitro, and show that the cytotoxic effects of TNFalpha are attenuated by LPS preconditioning. We show that LPS preconditioning significantly increases circulating levels of TNFalpha before middle cerebral artery occlusion in mice and show that TNFalpha is required to establish subsequent neuroprotection against ischemia, as mice lacking TNFalpha are not protected from ischemic injury by LPS preconditioning. After stroke, LPS preconditioned mice have a significant reduction in the levels of TNFalpha (approximately threefold) and the proximal TNFalpha signaling molecules, neuronal TNF-receptor 1 (TNFR1), and TNFR-associated death domain (TRADD). Soluble TNFR1 (s-TNFR1) levels were significantly increased after stroke in LPS-preconditioned mice (approximately 2.5-fold), which may neutralize the effect of TNFalpha and reduce TNFalpha-mediated injury in ischemia. Importantly, LPS-preconditioned mice show marked resistance to brain injury caused by intracerebral administration of exogenous TNFalpha after stroke. We establish an in vitro model of LPS preconditioning in primary cortical neuronal cultures and show that LPS preconditioning causes significant protection against injurious TNFalpha in the setting of ischemia. Our studies suggest that TNFalpha is a twin-edged sword in the setting of stroke: TNFalpha upregulation is needed to establish LPS-induced tolerance before ischemia, whereas suppression of TNFalpha signaling during ischemia confers neuroprotection after LPS preconditioning.

Mice deficient in corticotropin-releasing factor receptor type 2 exhibit normal ethanol-associated behaviors.

BACKGROUND: Stress is believed to influence alcohol use and relapse in alcoholics. Animal studies suggest an interaction between corticotropin-releasing factor (CRF) and its receptors and the behavioral effects and consumption of alcohol. The objective of these studies was to examine the effect of corticotropin-releasing factor receptor type 2 (CRF2) on ethanol consumption, conditioned taste aversion, sedation, and hypothermia. METHODS: CRF2-null mutant or knock-out (KO), and wild-type (WT) mice were used to assess consumption of increasing concentrations of ethanol in a two-bottle, 24-hr test and during daily limited-access sessions. Ethanol-induced conditioned taste aversion (CTA), loss of righting reflex (LORR), hypothermia, and ethanol metabolism kinetics were also examined in the CRF2 KO and WT mice. RESULTS: CRF2 KO mice did not differ from WT mice in sensitivity to ethanol-induced CTA, LORR, hypothermia, or ethanol metabolism kinetics. There was no genotypic difference in ethanol intake or preference in the 24-hr, two-bottle choice procedure, and only modestly increased [corrected] consumption of the 7.5 and 10% ethanol solutions in KO versus WT mice in the limited-access procedure. CONCLUSIONS: CRF2 deficiency had little effect on several ethanol-associated behaviors in CRF2-null mutant compared with WT mice, suggesting that this receptor does not have a primary role in modulating these behaviors. Evidence of a role for this receptor in neural circuits subserving stress-coping behaviors suggest that future studies should focus on the role of endogenous CRF2 in ethanol-associated behaviors in mice that are stressed or withdrawing from dependence on ethanol.

Corticotropin-releasing factor overexpression decreases ethanol drinking and increases sensitivity to the sedative effects of ethanol.

RATIONALE: Corticotropin-releasing factor (CRF) may play a significant role in drug and alcohol abuse. OBJECTIVE: To evaluate the role of CRF in these processes, we examined several ethanol (EtOH) related behaviors in mice that carry a transgene that causes overexpression of CRF. METHODS: We examined voluntary EtOH drinking, loss of the righting reflex (LORR), EtOH-induced conditioned taste aversion (CTA), and EtOH clearance in littermate transgenic (TG) and non-transgenic (non-TG) mice. In addition, because preliminary results indicated that age exacerbated differences in EtOH consumption between the two genotypes, we performed a cross-sectional and longitudinal evaluation of this trait at two ages ( approximately 100 and 200 days old). RESULTS: We found that TG mice consumed significantly less EtOH and had a lower preference for EtOH-containing solutions compared with their non-TG littermates. We also found that the older drug-naive TG mice drank less EtOH as compared with the younger mice of the same genotype; however, the same relationship did not exist for drug-naive non-TG mice. Prior experience in drinking EtOH when 100 days old led to decreased EtOH drinking when 200 days old in both genotypes. Duration of LORR was longer in the TG mice, EtOH-induced CTA was marginally greater in non-TG mice at the highest dose tested, and there were significant but small differences in EtOH clearance parameters. CONCLUSIONS: These data show that CRF overexpressing mice voluntarily consume less EtOH. This difference is associated with greater sensitivity to the sedative-hypnotic effects of EtOH, but not with increased sensitivity to the aversive effects of EtOH.

Activation of the CRF 2 receptor modulates skeletal muscle mass under physiological and pathological conditions.

Two receptors activated by the corticotropin-releasing factor (CRF) family of peptides have been identified, the CRF 1 receptor (CRF1R) and the CRF 2 receptor (CRF2R). Of these, the CRF2R is expressed in skeletal muscle. To understand the role of the CRF2R in skeletal muscle, we utilized CRFR knockout mice and CRF2R-selective agonists to modulate nerve damage and corticosteroid- and disuse-induced skeletal muscle atrophy in mice. These analyses demonstrated that activation of the CRF2R decreased nerve damage and corticosteroid- and disuse-induced skeletal muscle mass and function loss. In addition, selective activation of the CRF2R increased nonatrophy skeletal muscle mass. Thus we describe for the first time a novel activity of the CRF2R, modulation of skeletal muscle mass.

Corticotropin-releasing hormone-related peptides and receptors: emergent regulators of cardiovascular adaptations to stress.

Since its discovery 2 decades ago, potent effects of corticotropin-releasing hormone (CRH) on the heart and vasculature have been consistently observed. The recent discoveries of novel CRH-related peptides residing in the heart and a distinct cardiac CRH receptor (CRH-R2), have renewed interest in the role of the CRH family on cardiovascular function. This review highlights the emerging view of a peripheral, cardiac CRH system and its potential relevance in mediating the adaptive response of the heart to stress.