電撃提示部位関数としてのシロネズミの胃損傷に及ぼす信号-電撃随伴確率の効果

津田 彰; 平井 久

doi:10.4992/jjpsy.47.258

EFFECTS OF SIGNAL-SHOCK CONTINGENCY PROBABILITY ON GASTRIC LESIONS IN RATS AS A FUNCTION OF SHOCK REGION

AKIRA TSUDA, HISASHI HIRAI

Author information

JOURNAL FREE ACCESS

1976 Volume 47 Issue 5 Pages 258-267

DOI https://doi.org/10.4992/jjpsy.47.258

Details

Published: January 20, 1977 Received: January 14, 1976 Available on J-STAGE: July 16, 2010 Accepted: - Advance online publication: - Revised: -
Correction information
Date of correction: July 16, 2010 Reason for correction: - Correction: ABSTRACT Details: Wrong : Fear is known to produce psychosomatic diseases, such as gastric lesions or bradycardic responses. But how devastating and debilitating a given stress is, depends markedly on whether the animal can “prepare itself” for the stressor.
This proposition has been verified experimentally by Weiss (1970); he gave restrained rats signalled or unsignalled shocks through fixed tail electrodes. Shocks occurred once a minute for 19hrs. Rats that received shocks unpredictably showed greater somatic stress reactions than animals that received the same shocks but could predict their occurrence by a signal. In contrast to this result, Brady et al. (1962) and Paré (1964) reported greater weight losses in rats receiving predictable shocks than in rats receiving unpredictable shocks. Therefore, experiments which studied the effects of signalled vs. unsignalled shocks have not reported consistent results.
It may be noted that the inconsistent effects of shock predictability may be due to the procedure used to deliver the reinforcing stressor (electric shock), In studies reporting deleterious effects of anxiety elicited by a signal, electric shock was presented through a grid floot to the foot pads of relatively unrestrained subjects, whereas with the exception of the Imada (1972) and the Seligman (1968) experiments, in the studies reporting stress-reduced effects of predictable shock, shock was presented through small electrodes attached to the tail of highly restrained rats.
The present study using 77 rats examined the effects of the signal-shock contingency probability on stress pathology, such as lesions in the stomach or body weight changes, as a function of stressor region. For pursuing this purpose, three degrees of signal-shock contingency probability (100, 50, or 0%) were factonally combined with two regions of stressor (tail shock, TS; or foot shock, FS) (Table 1). All subjects were deprived of food for 24hrs preceding the experimental session. The animals were then placed in the rat holders for 1hr habituation followed by a 23hrs stress period. Rats in the 100PS group were presented with a tone 10sec before the onset of a 2sec 2.6-mA mean TS (or FS). Paired tone-shock presentations occurred on a VI 50sec schedule over 23hrs consecutive hours. Subjects in the NPS group received the same number of signalled shock presentations as did 100PS group. However, the presentations of the signal bore no systematic relationships to the TS (or FS) onset. The 50PS group received TS (or FS) following a random 50% of the signal presentation while the rest of the signal occurred randomly with no relationship to the scheduling of the TS (or FS). The NS group rats were maintained in their restrainers for 23hrs receiving signals but no TS (or FS) exposure. Following the experimental session, subjects were returned to their home-cages for 3hrs with water ad lib. but no food. At the end of 3hrs, subjects were sacrificed.
Analysis of gastric lesions (Figs. 1 & 2) and body weightchanges, shown in Figs. 3 and 4, indicated that animals in NPS and 50PS groups which received unpredictable TS developed considerably more pathology than animals which received either the same TS preceded by a tone or no TS. However, the 100PS group that received FS predictably resulted in significantly greater gastric lesions and body weight losses, than NPS and 50PS groups that received the same FS but could not predict their occurrence by a tone.
These reversal effects show that the interaction between shock regions and signal shock contingency probability plays an important role, which seems to converge the inconsistent effects of shock predictability which were previously reported by some investigators. In other words, these findings could be reconciled by assuming that the signal-shock contingency probability has opposite effects on stress-induced physiological changes as a function of the shock regions.
Right : Effects of signal-shock contingency probability on stress pathology were studied with 2 regions of electric shock and with (a) only sound signal presentations (NS), (b) unrelated presentations of the signal and tail shock (TS) or foot shock (FS) (NPS), (c) signal presentations all of which were paired with the TS or FS (100PS), or (d) signal presentations, 50% of which were paired with a TS or FS (50PS). Rats in NPS and 50PS groups with TS showed more stress-induced pathology than animals in the 100PS group with TS. However, the 100PS group with FS resulted in greater gastric lesions than NPS, 50PS, or NS group. The interaction between shock region and signal-shock contingency probability plays an important role.

Abstract

Effects of signal-shock contingency probability on stress pathology were studied with 2 regions of electric shock and with (a) only sound signal presentations (NS), (b) unrelated presentations of the signal and tail shock (TS) or foot shock (FS) (NPS), (c) signal presentations all of which were paired with the TS or FS (100PS), or (d) signal presentations, 50% of which were paired with a TS or FS (50PS). Rats in NPS and 50PS groups with TS showed more stress-induced pathology than animals in the 100PS group with TS. However, the 100PS group with FS resulted in greater gastric lesions than NPS, 50PS, or NS group. The interaction between shock region and signal-shock contingency probability plays an important role.

Corresponding author

Correction information

Register with J-STAGE for free!