Some effects of exposure to a heat stressor upon the rat's subsequent reactions to that stressor

In six experiments, rats were placed on a heated plate on two occasions (test and retest), and the latencies with which they licked their paws were taken as an index of their sensitivity to nociceptive stimulation. Experiment 1 provided evidence that rats were selectively analgesic on retest depending upon the intensity of the heat experienced on the initial test. Experiment 2 showed that this analgesia was recruited rapidly and was long-lasting, as it was observed when retest was scheduled as early as 0.2 and as late as 48 h after the initial exposure to the hot-plate. Experiment 3 documented a role for conditioning processes, as this analgesia was removed by an extinction-like procedure conducted between test and retest. Experiments 4 and 5 provided evidence for a non-opioid mechanism of pain control, because the analgesia was not diminished by the opioid antagonist, naloxone, nor by a history of morphine injections. These experiments also revealed that the analgesia observed on retest was enhanced and reduced when rats were given naloxone and morphine, respectively, on the initial test. Finally, Experiment 6 showed that the analgesia on retest summated with that produced by morphine. The results were taken to mean that the hot-plate assay for analgesia can itself activate endogenous mechanisms of pain control, and some speculations were offered as to how this occurred.     

Prepared to eat: how immediate affective and motivational responses to food cues are influenced by food deprivation

Three studies examined how food deprivation influences the immediate valence of food stimuli as well as spontaneous motivational tendencies toward them. We assumed that immediate reactions towards food stimuli should be tuned to the basic needs of the organism. In Study 1, the immediate valence of food names as a function of need state was assessed using an Implicit Association Test (IAT) in a quasi‐experimental design. Food deprivation led to a more positive immediate valence of food items. In Study 2, these results were replicated using the Extrinsic Affective Simon Task. In Study 3, immediate motivational reactions toward pictorial food stimuli were assessed. As hypothesized, approach reactions were facilitated for participants tested before as compared to after lunch, even in a sample with eating disorders. We thus conclude that the immediate valence of edible objects partially reflects regulation in the service of need fulfillment. Copyright © 2006 John Wiley & Sons, Ltd.     

The effect of food and water deprivation and satiation on recognition

Food and water deprived and satiated subjects, as well as control subjects, were shown words presented tachistoscopically for .01 sec until word recognition. Five food-relevant, five water-relevant, and five neutral (animal) words of high string frequency were matched for letter confusability and letter predictability. Analyses of the data, in terms of number of presentations until recognition as well as number of words recognized at selected presentations, revealed that the amount but not the type of deprivation significantly altered word recognition. Moreover, the effect of motivation was significant already on the first slide presentation, while the effects of word characteristics (word category and generated value) occurred only after a number of presentations.