Predictable and Unpredictable Shock: Their Pathological Effects on Restrained and Unrestrained Rats

Abstract

The effects on rats of predictable and unpredictable shock were measured under 2 conditions: unrestrained Ss were shocked intermittently for 12/24 hr. on a 6-hr. on, 6-hr. off schedule; restrained Ss were shocked intermittently for 12/24 hr. on a 6-hr. on, 6-hr. off schedule. All Ss were shocked via tail electrode; thus, for the first time, unrestrained rats were completely unable to avoid “unavoidable” shock. Under Condition I, Ss receiving unpredictable shock lost more weight than Ss receiving predictable shock. Under Condition II, more Ss in the unpredictable-shock group developed ulcers than Ss in the predictable-shock group. The findings of Weiss (1968, 1970) were partially confirmed and extended to unrestrained Ss.

Effects of Acute Exposure to Stressors on Subsequent Avoidance-Escape Behavior*

“…Investigators have studied bodily changes resulting from differences in the ability to control a stressor (1)(2)(3)(4)(5), predictability of stressors (6)(7)(8)(9)(10), conflict (11)(12)(13)(14) and, most recently, psychological aspects of aggression (15). These studies have revealed that psychological variables are probably the major determinants of a variety of somatic stress responses, including development of gastric lesions, loss of body weight, elevation of plasma levels of steroids, and changes in norepinephrine level in the brain.…”

The Effects of Electric Shock Stress on Rapid Eye Movement (REM) Sleep in Hooded Rats

“…In light of the differential effect of predictable and unpredictable shock on a number of physiological variables (Bassett & Cairncross, 1973;Brady et al, 1962;Friedman & Ader, 1965;Mason et aI., 1961;Pare, 1964;Price, 1972;Weiss, 1970), the absence of any difference in terms of REM sleep suggests that REM suppression is not necessarily influenced in the same fashion as other stress indices.…”

“…These two kinds of shock could differentially influence REM sleep because they produce different effects on adrenocortical activation (Bassett & Cairncross, 1973), adrenomedullary activation (Mason, Mangan, Brady, Conrad, & McK. Rioch, 1961), weight loss (Brady, Thornton, & De Fisher, 1962;Friedman & Ader, 1965;Pare, 1964;Price, 1972), and gastric ulceration (Pare, 1964;Price, 1972;Weiss, 1970). In addition, predictable shock leads to a greater corticosteroid elevation than does unpredictable shock (Bassett & Cairncross, 1973), and a dose-dependent inverted relationship between corticosteroid level and amount of REM sleep has been demonstrated (Gillin, Jacobs, Fram, & Snyder, 1972;Gillin, Jacobs, Snyder, & Henkin, 1972).…”

Current animal models of anxiety, anxiety disorders, and anxiolytic drugs

“…Geller-Seifter test Punished responses for food [8] Vogel test Punished drinking [9] Four plate test Punished crossings [10] Defensive burying Shock prod burying [11] Hyponeophagia Feeding in an unfamiliar arena [12] Distress vocalization Ultrasonic vocalizations in isolated pups [13] Conditioned responses Active/passive avoidance Avoidance of aversive stimuli [14] Fear potentiated startle Startle in aversive environments [15] Conditioned fear Freezing in aversive environments [16] anxiety to test the efficacy of classical and novel anxiolytics [68][69][70]. The assumption that defense against natural threats models stress-induced anxiety better than, for example, electric shocks led to the development of predator-induced anxiety models in rats [63] and mice [71].…”

“…Overall, animal models have to fulfill three criteria: predictive validity (performance in the test predicts performance in the clinic), face validity (phenomenological similarity), and construct validity (theoretical rationale) [2]. It occurs that the 'classical' models of anxiety (Table 1) [3][4][5][6][7][8][9][10][11][12][13][14][15][16] fail to fully meet these criteria. Predictive validity may have been satisfactory with benzodiazepines, but the large discrepancies between laboratory and clinical findings suggest that the predictive power of laboratory testing is rather modest with novel compounds ( Table 2) [17][18][19][20][21]22 && , .…”