Depletion of hypothalamic norepinephrine reduces the fever induced by polyriboinosinic acid: polyribocytidylic acid (Poly I:Poly C) in rats

Psychoneuroendocrine immunology: perception of stress can alter body temperature and natural killer cell activity

Psychoimmunology has been credited with using the mind as a way to alter immunity. The problem with this concept is that many of the current psychoimmunology techniques in use are aimed at alleviating stress effects on the immune system rather than at direct augmentation of immunity by the brain. Studies in animals provide a model that permits us to approach the difficulties associated with gaining an understanding of the CNS-immune system connection. A particular advantage of using animals over humans is that psychological and social contributions play a less prominent role for animals than for human subjects, since the animals are all inbred and reared under identical controlled conditions. If the insightful information provided by animal studies is correct, then psychotherapy for the treatment of diseases might be made more effective if some aspect of this knowledge is included in the design of the treatment. We emphasize conditioning as a regimen and an acceptable way to train the brain to remember an output pathway to raise immunity. We propose that a specific drug or perception (mild stress, represented by rotation, total body heating or handling) could substitute and kindle the same output pathway without the need for conditioning. If this view is correct, then instead of using conditioning, it may be possible to use an antigen to activate desired immune cells, and substitute a drug or an external environmental sensory stimulus (perception) to energize the output pathway to these cells. Alternatively, monitoring alterations of body temperature in response to a drug or perception might allow us to follow how effectively the brain is performing in altering immunity. Studies with animals suggest that there are alternative ways to use the mind to raise natural or acquired immunity in man.

Endotoxin tolerance does not alter open field-induced fever in rats

Exposure to an open field has been shown to cause a rise in the body temperature of rats. In many respects, this rise in body temperature is similar to fevers caused by endotoxin and other inflammatory stimuli. Rats repeatedly injected with endotoxin develop tolerance to the fever-inducing action of endotoxin. We hypothesized that repeated pretreatment with endotoxin would modify the fever caused by exposure to psychological stress. To test this hypothesis, we compared open field-induced fevers in rats made endotoxin tolerant to those rats not endotoxin tolerant. We found that endotoxin tolerance had no effect on open field fevers.

Sodium carbonate prevents NK cell conditioning by interfering with the US signal

The conditioned enhancement of natural killer (NK) cell activity can be blocked by the injection of sodium carbonate solution prior to the association of the camphor odor conditioned stimulus (CS) with the polyinosinic:polycytidylic acid (poly I:C) unconditioned stimulus (US). We have experimentally dissociated the memory which is formed for camphor odor from that developed for the association of camphor with the US. The memory for the odor of camphor can be allowed to develop one day before the administration of the unconditioned stimulus. Sodium carbonate appears to act within the central nervous system to block the association of the unconditioned stimulus with the conditioned stimulus. The data also suggest that in conditioning of NK cell activity, there are two specific sites for memory of the response, one for the conditioned stimulus and the other for the association of the unconditioned stimulus with the conditioned stimulus.

The identity of the unconditioned stimulus to the central nervous system is interferon-beta

The specific mechanism of interaction between the central nervous system and immune system was examined using conditioned augmentation of natural killer (NK) cell activity. This study focused on the role of interferon-beta (IFN-beta) as the unconditioned stimulus (US). IFN-beta was found to be the signal responsible for the bidirectional communication which links the central nervous system with the immune system. This was substantiated by injection of small quantities of IFN-beta directly into the cisterna magna, which activated the effector pathway from the central nervous system to the immune system. More importantly, we found that when the conditioned stimulus (CS) was paired with an injection of IFN-beta into the cisterna magna, the conditioned animals were able to raise their natural killer cell activity in response to subsequent exposure to the conditioned stimulus. These studies show the unconditioned response must be the response of the central nervous system (CNS) to the unconditioned stimulus and not the direct effect of the substance injected into the periphery.

The direction of the conditioned natural killer cell response can be re-directed with indomethacin and/or handling

We have used the pairing of camphor odor conditioned stimulus (CS) and injection of poly I:C unconditioned stimulus (US) in a short 3 day single trial conditioning paradigm. Conditioning was done by exposing mice to the CS/US combination on day 0 and reexposing the conditioned animals to the CS on day 2. This results in a conditioned augmentation of the natural killer (NK) cell response. Indomethacin treatment and/or handling stress induced by simply measuring rectal temperature was found to dramatically alter the direction of the conditioned NK cell response. Conditioning of indomethacin treated mice produced a conditioned suppression of the NK cell response mimicking a conditioned tolerance response. If handling stress was superimposed on day 2 the conditioned suppression response was replaced by a conditioned augmentation of the NK cell response. Even with one trial conditioning, drugs and handling stress can serve as additional cues to alter the direction of the conditioned response. The studies also show that the conditioning of the fever response is independent of conditioning of the NK cell response.

Indomethacin and sodium carbonate effects on conditioned fever and NK cell activity

The augmentation of natural killer (NK) cell activity and elevation of body temperature (fever) can both be conditioned using camphor odor as the conditioned stimulus (CS) and poly I:C as the unconditioned stimulus (US). While both responses can be conditioned in parallel fashion as shown previously, our results indicate the conditioned learning of these responses may not follow along a common path. We found that injection of a 1% solution of sodium carbonate was able to consistently block the CS/US learning of the NK cell response but did not block conditioning of the fever response. In contrary fashion, mice treated with indomethacin (which inhibits prostaglandin-induced fever) dissolved in the sodium carbonate solution did not learn in consistent fashion the fever response. However, indomethacin-treated animals were able to recall the NK cell response. These results support the view that although the same mediator, IFN-beta, is responsible for the conditioned learning of the NK cell and fever responses both the learning and recall of the responses are initiated along separate pathways.

Influence of noradrenergic input into the hypothalamic paraventricular nucleus on fever in the guinea-pig

The febrile response of guinea-pigs to a bacterial pyrogen was tested under different experimental conditions: (1) during electrical stimulation of the hypothalamic paraventricular nucleus (PVN), (2) after destruction of noradrenergic afferents into the PVN by 6-hydroxydopamine (6-OHDA), (3) during a microinfusion of noradrenaline (NA) into the PVN. Electrical stimulation of the PVN neurons by implanted microelectrodes reduced the febrile response to 45% of the control values. This confirmed the proposed antipyretic function of these neurons. Chronic destruction of noradrenergic afferents to the PVN by microinjected 6-OHDA also resulted in a significant reduction of febrile responses to 38% of the control values. A microinfusion of NA into the PVN enhanced the febrile responses to bacterial endotoxin by 39% in comparison to animals microinfused with the solvent (0.9% NaCl). Immunoreactivity to an antiserum against arginine vasopressin (AVP) was compared in PVN neurons of 6-OHDA-treated and of control animals. The number of AVP-immunoreactive perikarya and the intensity of immunoreactivity were increased in the animals treated with 6-OHDA, especially in the medial part of the PVN. Since fever was increased by microinfused NA and decreased by 6-OHDA treatment, we assume an inhibitory influence of noradrenergic brain stem afferents on the proposed antipyretic vasopressinergic system of the PVN.

Conditioning the elevation of body temperature, a host defensive reflex response

We hypothesize that a number of host defense responses such as natural killer (NK) cell activity, cytotoxic lymphocyte (CTL) activity, antibody production, and elevated body temperature (TR) might be conditionable. We have designated such specifically learned response to be a defensive reflex response. Here we describe a simple single trial association paradigm for conditioning the TR response in BALB/c mice. Animals are conditioned on day 0 by exposing them to the odor of camphor for 1 hr, followed by injection of the pyrogen poly I:C 20 microgram ip. Control groups are injected with either poly I:C or saline and not exposed to the camphor odor. Reexposure of all groups to the conditioned stimulus (CS) on day 2 or 3 cause elevation of body temperature in the conditioned group mice but not in the nonconditioned or saline control groups. Since we have conditioned the natural killer cell response with the same paradigm, these results suggest that multiple defensive responses might be conditionable simultaneously and they might have important survival value for the species.