Don R. Justesen

Pharmacological Differentiation of Allergic and Classically Conditioned Asthma in the Guinea Pig

A whole-body plethysmographic technique was developed and then used to detect experimentally induced asthma in guinea pigs and to assess pharmacological treatments of allergic and classically conditioned attacks. Inhalation of a beta adrenergic compound (isoproterenol) controlled both forms of attack. Atropine and methscopolamine, parasympathetic blocking agents, prevented conditional but not allergic attacks; diphenhydramine, an antihistamine, prevented allergic attacks; and methysergide, which blocks serotonin (which is believed to trigger human asthma), prevented neither. The guinea pigs allergic reaction is probably the result of a bronchospasm induced by histamine released in tissue of the airway by a local combination of allergen and antibody. The conditional attack is believed to be a constriction of the airway mediated by parasympathetic fibers of central origin.

Classical and Instrumental Conditioning of Licking: A Review of Methodology and Data

One night several years ago I was part of an audience that was being entertained by the comedian Shelley Berman. During the delivery of a monologue by which he was regaling the audience with an impression of a beleaguered child psychologist, Berman suddenly interjected a comment about experimental psychologists: “... you know, those people who study rats for reasons of their own!” I confess that the feelings he invoked in me then about the sometimes seemingly abstruse activities of my discipline were later aroused again by Doctors Weijnen and Mendelson when they asked me to write a chapter on the licking behaviors of rodents. Subsequently, after reading more than 300 papers on licking that have appeared in the biopsychological literature during the past 25 years, I came to realize that the seeming abstruseness of the subject matter actually lay in the eye of the beholding psychologist.

Unavoidable gridshock without scrambling circuitry from a faradic source of low-radio-frequency current

A high-voltage radio-frequency stimulator was used as a source of motivational footshock in studies of conditional suppression. The circuit of the stimulator is presented schematically, then discussed in terms of affect induced by, gross behavioral response to, and electrical characteristics of, the stimulus. Near daily use of the stimulator across 6 months of formal assessment revealed that nonscrambled presentations of footshock via a grid of aluminum bars invariably resulted in stimulation of rat Ss and generated highly efficient conditional suppression of operant responding. While the stimulator was primarily designed to permit unconfounded presentation of gridshock in a 2,450-MHz microwave field, its simplicity and reliability suggest application in other situations requiring motivational shock.

An infrared device to monitor discrete ambulatory and stereotypic behaviors

An electronic device that can detect discrete ambulatory and stereotypic behaviors of animals is described. The system involves a minimum of two infrared (IR) beams, each connected to a set/reset flip-flop or latch. The initial occlusion of an IR beam simultaneously sets a latch, delivers a locomotion pulse output, and resets any previously set latch whose IR beam is not occluded. A set latch causes its associated IR beam to be refractory to further locomotion movements until reset by the occlusion of a second IR beam. All beams are continuously responsive to stereotypic activity.

Endogenous hyperthermia in normal human subjects. I: Experimental study of evoked potentials and reaction time

Previous work on awake guinea pigs and rats in the authors’ laboratory revealed that microwave-induced elevations of brain temperature (ΔTs from 1° to 3° C over resting baselines) are associated with reliable reductions in latencies of flash-evoked brain potentials’ (EPs). To assess the generality of this finding in the normal human being, and to avoid the ethical problem of whole-body human exposure to an intense microwave field, ΔTs were induced endogenously by vigorous exercise and by insulative and vapor-barrier clothing. Twenty male athletes, 18 to 22 years of age, were randomly but equally divided into counterbalanced experimental and control groups for a single 3-h morning or afternoon session of measurements. During baseline measures, EPs of three types were observed: flash-evoked N1, pattern-reversal P100, and event-related P300. In addition, simple reaction times (RTs) to photic stimulation were recorded. All measures were repeated after sham warming of the 10 control subjects and after tympanically indexed brain temperatures of the 10 experimental subjects were elevated by an average of 1.2° C above control values. EP and RT latencies were reliably reduced in association with the ΔTs, the mean reductions ranging from 3% to 9%. The data on the human flash-evoked N1 component compare favorably with data recorded from rats and guinea pigs that have undergone exogenous elevations of temperature by microwave irradiation. The data on RTs and other EP components are consistent with the thesis that human CNS activity in general is accelerated during a modest bout of whole-body hyperthermia.

Assessment of the contact eye cover as an effective method of restricting visual input

In the wake of several studies that have cast doubt upon the effectiveness of contact eye covers in restricting vision, we performed a series of five experiments to the end of achieving reversible blinding of the albino rat. The data of Experiment 1 indicated that the contact eye cover can be as effective as a rubber cup in restricting visual input. In Experiment 2, animals that were fitted binocularly with opaque eye covers performed as if blind on a task involving acquisition of pattern discrimination. In Experiment 3, binocular coverage with the opaque eye cover resulted in chance performance across 300 trials of a previously acquired pattern-discrimination habit. In Experiment 4, the base diameter of the eye cover was found to be a critical factor: Performance of a previously acquired brightness discrimination was reduced to chance levels by contact eye covers that approximated 7.0 mm in diameter. In Experiment 5, a smaller eye cover (6-mm diam) had no effect in limiting the visually evoked electrocortical response of the albino rat, while an eye cover of 7.2-mm diam produced a reliable attenuation of the response. The collective results indicate that appropriately fabricated contact eye covers are a viable means of restricting visual input and may justifiably be considered contact occluders.

Murine vocalizations: Experimental validation of a novel detector

A new device to detect vocalizations by mice or rats is described. Of modest cost and incorporating integrated circuits and controls that permit rapid setting of center frequency and sensitivity, the device is based on phase-locked tone decoding and can operate at sonic or ultrasonic frequencies. Circuit operation and schematics are provided, as are data from two studies of mice in which reliable discrimination of distress and submission calls from background noise was demonstrated.

Attenuation of retroactive inhibition by a single electroconvulsive shock

A retroactively interfering reversal habit, a left or right turn in a single-unit water maze, was learned by 28 rats. The interpolated habit was immediately followed in 14 of the animals by a single electroshock convulsion. Reliable “interference with retroactive interference” was found: shock animals were superior in demonstrating retention of original learning. This finding is discussed with reference to major behavioral theories of ECS and interpreted as being more nearly supportive of amnesic, as opposed to fear-induction or competing-response, mechanisms.