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Moes MI, Elia A, Gennser M, Eiken O, Keramidas ME. Nitrous oxide consistently attenuates thermogenic and thermoperceptual responses to repetitive cold stress in humans. J Appl Physiol (1985) 2023; 135:631-641. [PMID: 37471214 PMCID: PMC10642508 DOI: 10.1152/japplphysiol.00309.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/26/2023] [Accepted: 07/17/2023] [Indexed: 07/22/2023] Open
Abstract
Divers are at enhanced risk of hypothermia, due to the independent action of the inspired inert gases on thermoregulation. Thus, narcosis induced by acute (≤2 h) exposure to either hyperbaric nitrogen or normobaric nitrous oxide (N2O) impairs shivering thermogenesis and accelerates body core cooling. Animal-based studies, however, have indicated that repeated and sustained N2O administration may prevent N2O-evoked hypometabolism. We, therefore, examined the effects of prolonged intermittent exposure to 30% N2O on human thermoeffector plasticity in response to moderate cold. Fourteen men participated in two ∼12-h sessions, during which they performed sequentially three 120-min cold-water immersions (CWIs) in 20°C water, separated by 120-min rewarming. During CWIs, subjects were breathing either normal air or a normoxic gas mixture containing 30% N2O. Rectal and skin temperatures, metabolic heat production (via indirect calorimetry), finger and forearm cutaneous vascular conductance (CVC; laser-Doppler fluxmetry/mean arterial pressure), and thermal sensation and comfort were monitored. N2O aggravated the drop in rectal temperature (P = 0.01), especially during the first (by ∼0.3°C) and third (by ∼0.4°C) CWIs. N2O invariably blunted the cold-induced elevation of metabolic heat production by ∼22%-25% (P < 0.001). During the initial ∼30 min of the first and second CWIs, N2O attenuated the cold-induced drop in finger (P ≤ 0.001), but not in forearm CVC. N2O alleviated the sensation of coldness and thermal discomfort throughout (P < 0.001). Thus, the present results demonstrate that, regardless of the cumulative duration of gas exposure, a subanesthetic dose of N2O depresses human thermoregulatory functions and precipitates the development of hypothermia.NEW & NOTEWORTHY Human thermoeffector plasticity was evaluated in response to prolonged iterative exposure to 30% N2O and moderate cold stress. Regardless of the duration of gas exposure, N2O-induced narcosis impaired in a persistent manner shivering thermogenesis and thermoperception.
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Affiliation(s)
- Maaike I Moes
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Antonis Elia
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Mikael Gennser
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Ola Eiken
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Michail E Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
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Ballantyne JC, Sullivan MD. Is Chronic Pain a Disease? THE JOURNAL OF PAIN 2022; 23:1651-1665. [PMID: 35577236 DOI: 10.1016/j.jpain.2022.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/24/2022] [Accepted: 05/06/2022] [Indexed: 11/30/2022]
Abstract
It was not until the twentieth century that pain was considered a disease. Before that it was managed medically as a symptom. The motivations for declaring chronic pain a disease, whether of the body or of the brain, include increasing its legitimacy as clinical problem and research focus worthy of attention from healthcare and research organizations alike. But 1 problem with disease concepts is that having a disease favors medical solutions and tends to reduce patient participation. We argue that chronic pain, particularly chronic primary pain (recently designated a first tier pain diagnosis in International Diagnostic Codes 11), is a learned state that is not intransigent even if it has biological correlates. Chronic pain is sometimes a symptom, and may sometimes be its own disease. But here we question the value of a disease focus for much of chronic pain for which patient involvement is essential, and which may need a much broader societal approach than is suggested by the disease designation. PERSPECTIVE: This article examines whether designating chronic pain a disease of the body or brain is helpful or harmful to patients. Can the disease designation help advance treatment, and is it needed to achieve future therapeutic breakthrough? Or does it make patients over-reliant on medical intervention and reduce their engagement in the process of recovery?
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Affiliation(s)
- Jane C Ballantyne
- Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, Washington.
| | - Mark D Sullivan
- Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, Washington
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Ballantyne JC, Koob GF. Allostasis theory in opioid tolerance. Pain 2021; 162:2315-2319. [PMID: 33769368 DOI: 10.1097/j.pain.0000000000002280] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 03/17/2021] [Indexed: 01/29/2023]
Affiliation(s)
- Jane C Ballantyne
- Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, WA, United States
| | - George F Koob
- National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, United States
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Ramsay DS, Kaiyala KJ, Woods SC. Individual differences in biological regulation: Predicting vulnerability to drug addiction, obesity, and other dysregulatory disorders. Exp Clin Psychopharmacol 2020; 28:388-403. [PMID: 32338936 PMCID: PMC8389185 DOI: 10.1037/pha0000371] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Physiological regulation is so fundamental to survival that natural selection has greatly favored the evolution of robust regulatory systems that use both reactive and preemptive responses to mitigate the disruptive impact of biological and environmental challenges on physiological function. In good health, robust regulatory systems provide little insight into the typically hidden complex array of sensor-effector interactions that accomplish successful regulation. Numerous health disorders have been traced to defective regulatory mechanisms, and generations of scientists have worked to discover ways to correct these defects and restore normal physiological function. Despite progress, numerous chronic health disorders remain resistant to treatment, and indeed for some disorders the incidence is increasing. We propose that an individual's susceptibility to acquire certain persistent dysregulatory disorders can be traced to interindividual variation in how that individual's regulatory system responds to challenges. Preexisting reliable individual differences among regulatory systems are typically unrecognized until appropriate regulatory challenges (e.g., exposure to a drug of abuse) lead to dysregulation (e.g., drug addiction). Specific characteristics of an individual's regulatory responsiveness may include etiological factors that participate in the acquisition, escalation and maintenance of health disorders characterized by dysregulation. By appropriately challenging a healthy individual's regulatory systems to identify its underlying characteristics, it is possible to ascertain whether an individual has an elevated risk for acquiring a dysregulated health condition and thereby enable strategies designed to prevent, rather than treat, the condition. This model is applied to drug addiction, and in addition we relate this approach to other dysregulated conditions such as obesity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
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Affiliation(s)
- Douglas S. Ramsay
- Department of Oral Health Sciences, University of Washington
- Department of Orthodontics, University of Washington
- Department of Pediatric Dentistry, University of Washington
| | - Karl J. Kaiyala
- Department of Oral Health Sciences, University of Washington
| | - Stephen C. Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati Medical Center
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Pituitary Adenylate Cyclase-Activating Peptide (PACAP) Signaling and the Dark Side of Addiction. J Mol Neurosci 2018; 68:453-464. [PMID: 30074172 DOI: 10.1007/s12031-018-1147-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/27/2018] [Indexed: 12/15/2022]
Abstract
While addiction to drugs of abuse represents a significant health problem worldwide, the behavioral and neural mechanisms that underlie addiction and relapse are largely unclear. The concept of the dark side of addiction, developed and explored by George Koob and colleagues, describes a systematic decrease in reward-related processing following drug self-administration and subsequent recruitment of anti-reward (i.e., stress) systems. Indeed, the activation of central nervous system (CNS) stress-response systems by drugs of abuse is contributory not only to mood and anxiety-related disorders but critical to both the maintenance of addiction and relapse following abstinence. In both human and animal studies, compounds that activate the bed nucleus of the stria terminalis (BNST) have roles in stress-related behaviors and addiction processes. The activation of pituitary adenylate cyclase-activating peptide (PACAP) systems in the BNST mediates many consequences of chronic stressor exposure that may engage in part downstream corticotropin-releasing hormone (CRH) signaling. Similar to footshock stress, the BNST administration of PACAP or the PAC1 receptor-specific agonist maxadilan can facilitate relapse following extinction of cocaine-seeking behavior. Further, in the same paradigm, the footshock-induced relapse could be attenuated following BNST pretreatment with PAC1 receptor antagonist PACAP6-38, implicating PACAP systems as critical components underlying stress-induced reinstatement. In congruence with previous work, the PAC1 receptor internalization and endosomal MEK/ERK signaling appear contributory mechanisms to the addiction processes. The studies offer new insights and approaches to addiction and relapse therapeutics.
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Al-Noori S, Cimpan A, Maltzer Z, Kaiyala KJ, Ramsay DS. Plasma corticosterone, epinephrine, and norepinephrine levels increase during administration of nitrous oxide in rats. Stress 2018; 21:274-278. [PMID: 29145764 PMCID: PMC6310116 DOI: 10.1080/10253890.2017.1402175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Nitrous oxide (N2O) is a gaseous drug with abuse potential. Despite its common clinical use, little is known about whether N2O administration activates the HPA axis and/or the sympathetic adrenomedullary system. The goal of this study was to determine whether 60% N2O alters plasma concentrations of corticosterone (CORT), epinephrine (EPI), and norepinephrine (NE) in male Long-Evans rats. A gas-tight swivel assembly in the lid of a gas administration chamber allowed the remote collection of blood samples from an indwelling jugular vein catheter at four time-points: baseline and at 30, 60, and 120 min during a two-hour administration of 60% N2O. Relative to baseline, plasma CORT (n = 9) was significantly elevated at all three time-points during N2O inhalation (mixed model analysis, p = .001) and plasma EPI and NE levels were each significantly elevated (n = 8, p ≤ .001) at the 30 min assessment. EPI then declined and did not differ from baseline at the 60 and 120 min assessments (p > .05) whereas NE remained elevated (120 min, p = .001). Administration of 60% N2O increases circulating CORT, EPI, and NE, supporting N2O as a physiological stressor. An N2O-induced increase in CORT is consistent with the observation that addictive drugs typically activate the HPA axis causing increased plasma levels of glucocorticoids. Allostatic models of drug addiction typically involve stress systems and the possible role of stress hormones in N2O-induced allostatic dysregulation is discussed.
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Affiliation(s)
- Salwa Al-Noori
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
- Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Andreas Cimpan
- Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Zoe Maltzer
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
| | - Karl J. Kaiyala
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
| | - Douglas S. Ramsay
- Department of Oral Health Sciences at the University of Washington, Seattle, WA, USA
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Concentration-related metabolic rate and behavioral thermoregulatory adaptations to serial administrations of nitrous oxide in rats. PLoS One 2018; 13:e0194794. [PMID: 29672605 PMCID: PMC5909668 DOI: 10.1371/journal.pone.0194794] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 03/10/2018] [Indexed: 11/19/2022] Open
Abstract
Background Initial administration of ≥60% nitrous oxide (N2O) to rats evokes hypothermia, but after repeated administrations the gas instead evokes hyperthermia. This sign reversal is driven mainly by increased heat production. To determine whether rats will behaviorally oppose or assist the development of hyperthermia, we previously performed thermal gradient testing. Inhalation of N2O at ≥60% causes rats to select cooler ambient temperatures both during initial administrations and during subsequent administrations in which the hyperthermic state exists. Thus, an available behavioral response opposes (but does not completely prevent) the acquired hyperthermia that develops over repeated high-concentration N2O administrations. However, recreational and clinical uses of N2O span a wide range of concentrations. Therefore, we sought to determine the thermoregulatory adaptations to chronic N2O administration over a wide range of concentrations. Methods This study had two phases. In the first phase we adapted rats to twelve 3-h N2O administrations at either 0%, 15%, 30%, 45%, 60% or 75% N2O (n = 12 per group); outcomes were core temperature (via telemetry) and heat production (via respirometry). In the second phase, we used a thermal gradient (range 8°C—38°C) to assess each adapted group’s thermal preference, core temperature and locomotion on a single occasion during N2O inhalation at the assigned concentration. Results In phase 1, repeated N2O administrations led to dose related hyperthermic and hypermetabolic states during inhalation of ≥45% N2O compared to controls (≥ 30% N2O compared to baseline). In phase 2, rats in these groups selected cooler ambient temperatures during N2O inhalation but still developed some hyperthermia. However, a concentration-related increase of locomotion was evident in the gradient, and theoretical calculations and regression analyses both suggest that locomotion contributed to the residual hyperthermia. Conclusions Acquired N2O hyperthermia in rats is remarkably robust, and occurs even despite the availability of ambient temperatures that might fully counter the hyperthermia. Increased locomotion in the gradient may contribute to hyperthermia. Our data are consistent with an allostatic dis-coordination of autonomic and behavioral thermoregulatory mechanisms during drug administration. Our results have implications for research on N2O abuse as well as research on the role of allostasis in drug addiction.
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Fluegge K. Does environmental exposure to the greenhouse gas, N 2O, contribute to etiological factors in neurodevelopmental disorders? A mini-review of the evidence. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2016; 47:6-18. [PMID: 27566494 DOI: 10.1016/j.etap.2016.08.013] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Revised: 08/11/2016] [Accepted: 08/13/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND Neurodevelopmental disorders are increasing in prevalence worldwide. Previous work suggests that exposure to the environmental air pollutant and greenhouse gas - nitrous oxide (N2O) - may be an etiological factor in neurodevelopmental disorders through the targeting of several neural correlates. METHODOLOGY While a number of recent systematic reviews have addressed the role of general anesthesia in the surgical setting and neurodevelopmental outcomes, a narrative mini-review was conducted to first define and characterize the relevant variables (i.e., N2O, attention-deficit hyperactivity disorder [ADHD] and autism spectrum disorders [ASD]) and their potential interactions into a coherent, hypothesis-generating work. The narrative mini-review merges basic principles in environmental science, anesthesiology, and psychiatry to more fully develop the novel hypotheses that neurodevelopmental impairment found in conditions like ADHD and ASD may be due to exposure to the increasing air pollutant, N2O. RESULTS The results of the present mini-review indicate that exposure to N2O, even at non-toxic doses, may modulate central neurotransmission and target many neural substrates directly implicated in neurodevelopmental disorders, including the glutamatergic, opioidergic, cholinergic, and dopaminergic systems. Epidemiological studies also indicate that early and repeated exposure to general anesthesia, including N2O, may contribute to later adverse neurodevelopmental outcomes in children. CONCLUSIONS The current evidence and subsequent hypotheses suggest that a renewed interest be taken in the toxicological assessment of environmental N2O exposure using validated biomarkers and psychiatric endpoints. Given the relevance of N2O as a greenhouse gas, societies may also wish to engage in a more robust monitoring and reporting of N2O levels in the environment for climactic benefit as well.
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Affiliation(s)
- Keith Fluegge
- Institute of Health and Environmental Research, Cleveland, OH 44118, USA.
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9
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Al-Noori S, Ramsay DS, Cimpan A, Maltzer Z, Zou J, Kaiyala KJ. Brown adipose tissue thermogenesis does not explain the intra-administration hyperthermic sign-reversal induced by serial administrations of 60% nitrous oxide to rats. J Therm Biol 2016; 60:195-203. [PMID: 27503733 DOI: 10.1016/j.jtherbio.2016.07.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 07/15/2016] [Accepted: 07/18/2016] [Indexed: 02/07/2023]
Abstract
Initial administration of ≥60% nitrous oxide (N2O) to rats promotes hypothermia primarily by increasing whole-body heat loss. We hypothesized that the drug promotes heat loss via the tail and might initially inhibit thermogenesis via brown adipose tissue (BAT), major organs of thermoregulation in rodents. Following repeated administrations, N2O inhalation evokes hyperthermia underlain by increased whole-body heat production. We hypothesized that elevated BAT thermogenesis plays a role in this thermoregulatory sign reversal. Using dual probe telemetric temperature implants and infrared (IR) thermography, we assessed the effects of nine repeated 60% N2O administrations compared to control (con) administrations on core temperature, BAT temperature, lumbar back temperature and tail temperature. Telemetric core temperature, telemetric BAT temperature, and IR BAT temperature were reduced significantly during initial 60% N2O inhalation (p≤0.001 compared to con). IR thermography revealed that acute N2O administration unexpectedly reduced tail temperature (p=0.0001) and also inhibited IR lumbar temperature (p<0.0001). In the 9th session, N2O inhalation significantly increased telemetric core temperature (p=0.007) indicative of a hyperthermic sign reversal, yet compared to control administrations, telemetric BAT temperature (p=0.86), IR BAT temperature (p=0.85) and tail temperature (p=0.47) did not differ significantly. Thus, an initial administration of 60% N2O at 21°C may promote hypothermia via reduced BAT thermogenesis accompanied by tail vasoconstriction as a compensatory mechanism to limit body heat loss. Following repeated N2O administrations rats exhibit a hyperthermic core temperature but a normalized BAT temperature, suggesting induction of a hyperthermia-promoting thermogenic adaptation of unknown origin.
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Affiliation(s)
- Salwa Al-Noori
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA; Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Douglas S Ramsay
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA
| | - Andreas Cimpan
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA; Division of Biological Sciences, School of STEM, University of Washington, Bothell, WA, USA
| | - Zoe Maltzer
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA
| | - Jessie Zou
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA
| | - Karl J Kaiyala
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA.
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Ramsay DS, Al-Noori S, Shao J, Leroux BG, Woods SC, Kaiyala KJ. Predicting addictive vulnerability: individual differences in initial responding to a drug's pharmacological effects. PLoS One 2015; 10:e0124740. [PMID: 25880426 PMCID: PMC4400068 DOI: 10.1371/journal.pone.0124740] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 03/04/2015] [Indexed: 12/31/2022] Open
Abstract
Considerable data suggest that individuals who appear minimally disrupted during an initial drug administration have elevated risk for abusing the drug later. A better understanding of this association could lead to more effective strategies for preventing and treating drug addiction. To investigate this phenomenon using a rigorous experimental model, we first administered the abused inhalant nitrous oxide (N2O) to rats in a total calorimetry and temperature system to identify groups that were sensitive or insensitive to the drug’s hypothermic effect. We then enrolled the two groups in a novel N2O self-administration paradigm. The initially insensitive rats self-administered significantly more N2O than sensitive rats, an important step in the transition to addiction. Continuous non-invasive measurement of core temperature and its underlying determinants during screening revealed that both groups had similarly increased heat loss during initial N2O administration, but that insensitive rats generated more heat and thereby remained relatively normothermic. Calorimetry testing conducted after self-administration revealed that whereas N2O’s effect on heat loss persisted comparably for both groups, initially insensitive rats actually over-responded by generating excess heat and becoming hyperthermic. Thus, rats with the greatest initial heat-producing compensatory response(s) appeared initially insensitive to N2O-induced hypothermia, subsequently self-administered more N2O, and developed hyperthermic overcompensation during N2O inhalation, consistent with increased abuse potential and an allostatic model of addictive vulnerability.
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Affiliation(s)
- Douglas S. Ramsay
- Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America
- * E-mail:
| | - Salwa Al-Noori
- Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America
| | - Jason Shao
- Department of Biostatistics, University of Washington, Seattle, WA, United States of America
| | - Brian G. Leroux
- Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America
- Department of Biostatistics, University of Washington, Seattle, WA, United States of America
| | - Stephen C. Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, United States of America
| | - Karl J. Kaiyala
- Department of Oral Health Sciences, University of Washington, Seattle, WA, United States of America
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Carvalho F, Kiyatkin EA, Rusyniak DE, Romanovsky AA. Temperature in the spotlight of drug abuse research. Temperature (Austin) 2015; 2:27-8. [PMID: 27226999 PMCID: PMC4843858 DOI: 10.1080/23328940.2015.1008872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Revised: 01/08/2015] [Accepted: 01/08/2015] [Indexed: 11/17/2022] Open
Abstract
This editorial summarizes Temperature's special issue entitled "Temperature and Toxicology with a Focus on Drugs of Abuse" (2014, volume 1, issue 3), dedicated to the multiple recent discoveries related to the thermoregulatory effects of xenobiotics. Several basic and clinical studies on xenobiotic-induced hyperthermia are reported that propose novel mechanisms and treatments.
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Affiliation(s)
- Félix Carvalho
- UCIBIO-REQUIMTE; Toxicology Laboratory; Department of Biological Sciences; Faculty of Pharmacy; University of Porto, Portugal
| | - Eugene A Kiyatkin
- Behavioral Neuroscience Branch; National Institute on Drug Abuse – Intramural Research Program; NIH; Baltimore, MD USA
| | - Daniel E Rusyniak
- Department of Emergency Medicine; Pharmacology and Toxicology; Indiana University School of Medicine; Indianapolis, IN USA
| | - Andrej A Romanovsky
- Systemic Inflammation Laboratory (FeverLab); Trauma Research; St. Joseph's Hospital and Medical Center; Phoenix, AZ USA
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Flouris AD. A unifying theory for the functional architecture of endothermic thermoregulation. Temperature (Austin) 2014; 1:162-3. [PMID: 27624651 PMCID: PMC5008715 DOI: 10.4161/23328940.2014.980138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Revised: 10/21/2014] [Accepted: 10/21/2014] [Indexed: 11/21/2022] Open
Abstract
Developing a unifying theory for the functional architecture of endothermic thermoregulation has been proven to be a challenging endeavor. Three papers published in this issue of Temperature take a closer look at this problem and add interesting views to our knowledge about the way that endothermic thermoregulation works.
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Affiliation(s)
- Andreas D Flouris
- FAME Laboratory; Department of Exercise Science; University of Thessaly ; Trikala, Greece
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Ramsay DS, Woods SC, Kaiyala KJ. Repeated nitrous oxide exposure in rats causes a thermoregulatory sign-reversal with concurrent activation of opposing thermoregulatory effectors. Temperature (Austin) 2014; 1:257-267. [PMID: 25938127 PMCID: PMC4414259 DOI: 10.4161/23328940.2014.944809] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Initial administration of 60% nitrous oxide (N2O) to rats at an ambient temperature of 21°C decreases core temperature (Tc), primarily via increased heat loss (HL). Over repeated N2O administrations, rats first develop tolerance to this hypothermia and subsequently exhibit hyperthermia (a sign-reversal) due primarily to progressive increases in heat production (HP). When rats initially receive 60% N2O in a thermal gradient, they become hypothermic while selecting cooler ambient temperatures that facilitate HL. This study investigated whether rats repeatedly administered 60% N2O in a thermal gradient would use the gradient to behaviorally facilitate, or oppose, the development of chronic tolerance and a hyperthermic sign-reversal. Male Long-Evans rats (N = 16) received twelve 3-h administrations of 60% N2O in a gas-tight, live-in thermal gradient. Hypothermia (Sessions 1–3), complete chronic tolerance (Sessions 4–6), and a subsequent transient hyperthermic sign-reversal (Sessions 7–12) sequentially developed. Despite the progressive recovery and eventual hyperthermic sign-reversal of Tc, rats consistently selected cooler ambient temperatures during all N2O administrations. A final 60% N2O administration in a total calorimeter indicated that the hyperthermic sign-reversal resulted primarily from increased HP. Thus, rats did not facilitate chronic tolerance development by moving to warmer locations in the gradient, and instead selected cooler ambient temperatures while simultaneously increasing autonomic HP. The inefficient concurrent activation of opposing effectors and the development of a sign-reversal are incompatible with homeostatic models of drug-adaptation and may be better interpreted using a model of drug-induced allostasis.
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Affiliation(s)
- Douglas S Ramsay
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA ; Department of Orthodontics, University of Washington, Seattle, WA, USA ; Department of Pediatric Dentistry, University of Washington, Seattle, WA, USA
| | - Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, Ohio, USA
| | - Karl J Kaiyala
- Department of Oral Health Sciences, University of Washington, Seattle, WA, USA
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14
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Kaiyala KJ, Woods SC, Ramsay DS. Persistence of a hyperthermic sign-reversal during nitrous oxide inhalation despite cue-exposure treatment with and without a drug-onset cue. Temperature (Austin) 2014; 1:268-275. [PMID: 25938128 PMCID: PMC4416485 DOI: 10.4161/23328940.2014.944811] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/19/2014] [Accepted: 06/26/2014] [Indexed: 11/19/2022] Open
Abstract
We asked whether chronic tolerance and the hyperthermic sign-reversal induced by repeated 60% N2O exposures could be extinguished using a cue-exposure paradigm. Rats received 18 N2O administrations in a total calorimetry system that simultaneously measures core temperature (Tc), metabolic heat production (HP), and body heat loss (HL). Each exposure entailed a 2-h baseline period followed by a 1.5-h N2O exposure. The 18 drug exposures induced a robust intra-administration hyperthermia in which the initial hypothermic effect of N2O inverted to a significant hyperthermic sign-reversal during N2O inhalation due primarily to an acquired robust increase in HP. The rats were then randomized to one of three extinction procedures (n=8/procedure) over a 20-d interval: 1) a N2O-abstinent home-cage group (HC) that received only the usual animal care; 2) a cue-exposure group (CEXP) in which the animals were placed in the calorimeter 8 times but received no N2O; and 3) a drug-onset-cue group (DOC) in which animals received a brief N2O exposure in the calorimeter that mimicked the first 3 min of an actual 60% N2O trial. Following the extinction sessions, all rats received a 60% N2O test trial and Tc, HP and HL were assessed. The hyperthermic sign-reversal remained fully intact during the test trial, with no significant differences observed among groups in any post-baseline change in any thermal outcome. These data suggest that cue exposure may not be an efficacious strategy to reduce sign-reversals that develop with chronic drug use.
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Affiliation(s)
- Karl J Kaiyala
- Department of Oral Health Sciences; University of Washington; Seattle, WA USA
| | - Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience; University of Cincinnati; Cincinnati, OH USA
| | - Douglas S Ramsay
- Department of Oral Health Sciences; University of Washington; Seattle, WA USA
- Department of Orthodontics; University of Washington; Seattle, WA, USA
- Pediatric Dentistry; University of Washington; Seattle, WA USA
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