Changes in cutaneous and body temperature during and after conditioned fear to context in the rat

Infrared thermography was used to image changes in cutaneous temperature during a conditioned fear response to context. Changes in heart rate, arterial pressure, activity and body (i.p.) temperature were recorded at the same time by radio‐telemetry, in addition to freezing immobility. A marked drop in tail and paws temperature (−5.3 and −7.5 °C, respectively, down to room temperature), which lasted for the entire duration of the response (30 min), was observed in fear‐conditioned rats. In sham‐conditioned rats, the drop was on average half the magnitude and duration. In contrast, temperature of the eye, head and back increased (between + 0.8 and + 1.5 °C), with no difference between the two groups of rats. There was a similar increase in body temperature although it was slightly higher and delayed in the fear‐conditioned animals. Finally, ending of the fear response was associated with a gradual decrease in body temperature and a rebound increase in the temperature of the tail (+ 3.3 °C above baseline). This study shows that fear, and to some extent arousal, evokes a strong cutaneous vasoconstriction that is restricted to the tail and paws. This regionally specific reduction in blood flow may be part of a preparatory response to a possible fight and flight to reduce blood loss in the most exposed parts of the rat's body in case of injury. The data also show that the tail is the main part of the body used for dissipating internal heat accumulated during fear once the animal has returned to a safe environment.

[1]  W. Blessing,et al.  5-hydroxytryptamine2A receptors regulate sympathetic nerves constricting the cutaneous vascular bed in rabbits and rats , 2003, Neuroscience.

[2]  M. Fanselow,et al.  Body temperature as a conditional response measure for pavlovian fear conditioning. , 2000, Learning & memory.

[3]  A. B. Hertzman,et al.  THE ABSENCE OF VASOCONSTRICTOR REFLEXES IN THE FOREHEAD CIRCULATION. EFFECTS OF COLD , 1942 .

[4]  Eugene Nalivaiko,et al.  Synchronous changes in ear and tail blood flow following salient and noxious stimuli in rabbits , 1999, Brain Research.

[5]  R. Bonner,et al.  The relationship of laser-Doppler skin blood flow measurements to the cutaneous microvascular anatomy. , 1998, Microvascular research.

[6]  J. Hales,et al.  Cutaneous arteriovenous anastomoses present in the tail but absent from the ear of the rat. , 1977, Journal of anatomy.

[7]  D. Dawson,et al.  Comparison of digital infrared thermal imaging (DITI) with contact thermometry: pilot data from a sleep research laboratory. , 2003, Physiological measurement.

[8]  David I. Abramson,et al.  Responses of blood vessels in the resting hand and forearm to various stimuli , 1940 .

[9]  O. Horwitz,et al.  Relationship in the toe of skin surface temperature to mean blood flow measured with a plethysmograph. , 1954, Clinical science.

[10]  D C Blanchard,et al.  Defensive behavior of laboratory and wild Rattus norvegicus. , 1986, Journal of comparative psychology.

[11]  M. A. Baker,et al.  Variability of skin temperature in the waking monkey. , 1976, The American journal of physiology.

[12]  Gerald Kastberger,et al.  Infrared imaging technology and biological applications , 2003, Behavior research methods, instruments, & computers : a journal of the Psychonomic Society, Inc.

[13]  R. F. Westbrook,et al.  Stress-induced changes in respiratory quotient, energy expenditure and locomotor activity in rats: effects of midazolam , 1994, Psychopharmacology.

[14]  W. Blessing,et al.  Cutaneous vasoconstriction in conscious rabbits during alerting responses detected by hippocampal theta-rhythm. , 1997, The American journal of physiology.

[15]  E. Nalivaiko,et al.  Tail artery blood flow measured by chronically implanted Doppler ultrasonic probes in unrestrained conscious rats , 2001, Journal of Neuroscience Methods.

[16]  P Plassmann,et al.  Digital infrared thermal imaging of human skin. , 2002, IEEE engineering in medicine and biology magazine : the quarterly magazine of the Engineering in Medicine & Biology Society.

[17]  W. Blessing,et al.  Neurons in amygdala mediate ear pinna vasoconstriction elicited by unconditioned salient stimuli in conscious rabbits , 2001, Autonomic Neuroscience.

[18]  W. Blessing,et al.  5-hydroxytryptamine(2A) receptors regulate sympathetic nerves constricting the cutaneous vascular bed in rabbits and rats. , 2003, Neuroscience.

[19]  Y. Ootsuka,et al.  Thermoregulatory Control of Sympathetic Fibres Supplying the Rat's Tail , 2002, The Journal of physiology.

[20]  P. Carrive.  Conditioned fear to environmental context: cardiovascular and behavioral components in the rat , 2000, Brain Research.

[21]  W. Blessing,et al.  Lower Brainstem Pathways Regulating Sympathetically Mediated Changes in Cutaneous Blood Flow , 2003, Cellular and Molecular Neurobiology.

[22]  J.F. Head,et al.  Infrared imaging: making progress in fulfilling its medical promise , 2002, IEEE Engineering in Medicine and Biology Magazine.

[23]  R. J. McDonald,et al.  Amygdala, hippocampus and discriminative fear conditioning to context , 2000, Behavioural Brain Research.

[24]  A. C. Burton,et al.  THE TAIL OF THE RAT, IN TEMPERATURE REGULATION AND ACCLIMATIZATION. , 1965, Canadian journal of physiology and pharmacology.

[25]  Michael Anbar,et al.  Assessment of Physiologic and Pathologic Radiative Heat Dissipation Using Dynamic Infrared Imaging , 2002, Annals of the New York Academy of Sciences.

[26]  A. B. Hertzman.  Some relations between skin temperature and blood flow. , 1953, American journal of physical medicine.

[27]  M. Verhoye,et al.  In‐vivo non‐invasive study of the thermoregulatory function of the blood vessels in the rat tail using magnetic resonance angiography , 2002, NMR in biomedicine.

[28]  M. Iriki,et al.  Thermally-induced cutaneous sympathetic activity related to blood flow through capillaries and arteriovenous anastomoses , 1978, Pflügers Archiv.

[29]  Wilfrid Jänig,et al.  Characteristics of function-specific pathways in the sympathetic nervous system , 1992, Trends in Neurosciences.

[30]  R. Wise,et al.  Brain temperature fluctuation: a reflection of functional neural activation , 2002, The European journal of neuroscience.

[31]  Christopher J. Gordon,et al.  Thermal biology of the laboratory rat , 1990, Physiology & Behavior.

[32]  P. Carrive.  Cardiovascular and behavioural components of conditioned fear to context after ganglionic and α-adrenergic blockade , 2002, Autonomic Neuroscience.

[33]  D. O'Leary,et al.  Mode of neural control mediating rat tail vasodilation during heating. , 1985, Journal of applied physiology.

[34]  P. Carrive,et al.  Role of ventrolateral periaqueductal gray neurons in the behavioral and cardiovascular responses to contextual conditioned fear and poststress recovery , 2003, Neuroscience.