Brain, P.F., Al-Maliki, S. and Benton, D. (1981). Attempts to determine the status of electroshock-induced attack in male laboratory mice. Behavioural Processes 6: 171-189.

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Brain, P.F., Al-Maliki, S. and Benton, D. (1981). Attempts to determine the status of electroshock-induced attack in male laboratory mice. Behavioural Processes 6: 171-189.
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  Behauioural Processes, 6 (1981) 171-189 Elsevier Scientific Publishing Company, Amsterdam - Printed in Belgium 171 ATTEMPTS TO DETERMINE THE STATUS OF ELECTROSHOCK- INDUCED ATTACK IN MALE LABORATORY MICE PAUL F. BRAIN, SAM1 AL-MALIKI* and DAVID BENTON+ Departments of Zoology and Psychology+, University College of Swansea, Swansea, SA2 8PP Great Britain) *Present address: College of Education, University of Basrah, Basrah (Iraq) (Accepted 17 October 1980) ABSTRACT Brain, P.F., Al-Maliki, S. and Benton, D., 1981. Attempts to determine the status of Electroshock-induced attack in male laboratory mice. Behav. Processes, 6: 171-189. An attempt was made using a combination of simple experimental manipulations and videotape recorder (VTR) analysis of bite targets employed to determine whether electro- shock-induced attack on anosmic opponents in laboratory mice was an offensive or a de- fensive behaviour. VTR analysis suggested that ventral surface biting was more evident in this form of attack than in social conflict. Individually- and group-housed males showed similar levels of fighting on exposure to electroshock, but dominant males from pairs showed greater attack than their subordinate partners. Zinc sulphate-induced anosmia, 36 h of food deprivation, castration and lithium chloride treatment reduced electroshock- induced attack. Although significant changes were not obtained, there was some evidence that acute treatment with dexamethasone or ACTH augmented this behaviour. The direc- tion of these changes is similar to that seen with social conflict, and it is suggested that electroshock-induced attack in the mouse (unlike the rat) is largely an aggressive offensive behaviour. The high incidence of ventral surface biting may be a consequence of the up- right postures assumed on subjecting the animals to electroshock. INTRODUCTION There has been much serious debate on the heterogeneity of the concept ‘a.ggression’ (Moyer, 1968). Recently, Brain (1981) has provided a critical analysis of types of situations in which attack behaviour is recorded in mice. Because of the problems associated with Moyer’s (1968) classification, he attempts to provide an alternative scheme. It has the advantage that (i) it is shorter; (ii) the categories have been evolved after reference to studies on large numbers of species, and (iii) the divisions are consistently related to the utility of the behaviour to the performing animal. Two of the categories advocated are: 0376-6357/81/0000-0000/$02.50 o 1981 Elsevier Scientific Publishing Company  172 Self defensive behaviour This category includes activities which have received labels such as ‘escape- directed’, ‘proximity (to conspecifics)-related’, and ‘pain-induced’ forms of attack because: (i) they are all in response to some threat to the individual; (ii) they all seem to be accompanied by a motivation that can be anthro- pomorphically called ‘fear’; (iii) attempted avoidance generally preceeds fighting in this type of en- counter; and (iv) attacks on ‘opponents’ rarely involve injury-limiting strategies. Although it does not fulfil all the criteria of aggression (see Brain, 1981), electroshock may be used to induce attack on anosmic male partners. In spite of its imperfections, attack-induced by electroshock is used to assess ‘aggression’ in many studies. Social conflict This category combines ‘mate selection-related’, ‘territorial’ and ‘inter- male’ forms of attack. These were grouped because: (i) these categories are not exclusive; (ii) all generally involve intraspecific competition for resources that have a direct bearing on reproductive success; (iii) attack of this kind is generally a male characteristic and is much in- fluenced by pituitary-gonadal function; (iv) these responses often utilise ‘ritualised’ forms of attack that serve to reduce the chances of serious physical damage to the conspecific; (v) seasonal variation can be evident in all three phenomena. The present series of experiments attempted to assess the effects of simple manipulations which are known to alter social conflict on electroshock- induced fighting in mice. Furthermore, a videotape analysis was employed to assess the bite targets used in these two forms of fighting. MATERIALS AND METHODS Su b et ts ‘TO’ strain albino laboratory mice were obtained from A. Tuck & Sons Ltd. (Rayleigh, Essex, England). These were bred in the Animal Facility of the University College of Swansea under highly controlled conditions (described by Al-Maliki, 1980a) to generate subjects for experiments. Mice were maintained under a reversed lighting schedule (white fluorescent lights on from 22.30-10.30 h) which meant that husbandry and behavioural observations were generally performed under dim red lighting to minimize interference. Ambient temperature was maintained between 18 and 22°C  173 as it influences fighting intensity in laboratory mice (Ginsberg and Allee, 1942). Opaque polypropylene type MI cages (North Kent Plastics, Essex, England) measuring 30 X 12 X 11 cm were routinely employed in these studies. The galvanized wire tops of these structures contained an ad libitum supply of food (Pilsbury’s breeding diet) and water. Mice utilized in these experiments were primiparous progeny of individuals that had been paired at 9 weeks of age. Litters were culled at birth to 6-S pups. Fathers were generally removed 10 days after birth of the litter, as the presence of adult males augments the development of the capacity for subsequent social conflict in mice (Mugford and Nowell, 1972). At weaning (18-22 days after birth), the sex of each animal was determined and mice were allocated to two larger containers (one for males and one for females) before being randomly allocated to single-sex groups of six in cleaned cages. Established groups remained undisturbed (except for maintenance) until employed in experiments or new breeding cycle. Further description and validations are available in Al-Maliki (1980a). Electroshock induced behaviour Shock duration and frequency were controlled by a multipurpose labora- tory unit (Colne Instrument Co. Ltd.) and the shocks were generated by a constant voltage device with scrambler (Camden Instruments Ltd.). The shock generator was of sufficient voltage to preclude changes in the mouse’s resistance being of significance. The shocks were delivered to the grid floor fitted to a modified North Kent Plastics type Ml mouse box (this was em- ployed to make the arena size, i.e. 30 X 12 X 11 cm, comparable to that used in social conflict tests). The grid consisted of 1 mm stainless steel rods set 0.5 cm apart. Test animals received 10 min encounters with docile anosmic ‘standard opponents’. These males rarely directed threat and attack towards test ani- mals even when subjected to electroshock. Temporary anosmia was induced in these group-housed animals by perfusion of the nostrils with a 4% zinc sulphate solution (Brain and Al-Maliki, 1978). The effects of varying currents, voltage, frequency of shocks etc. were initially investigated. Ultimately, a 0.8 ma current of 0.5 s duration delivered to the grid floor at 5 s intervals was selected as the optimal condition for generating attack by male mice (see Fig. 1 which shows the effect of varying current (O-2.0 ma) at constant voltage and also the sex differences in this response. The data were obtained from 70 male and 70 female mice. Ten naive animals of each sex were subjected to the selected current of 0.5 s duration, at 5 s intervals. The accumulated attacking time (AAT) result is given but other measures supported the conclusions of this study). A transparent, perspex lid was placed over the shock cage to prevent escape or clinging to the wire cover and tests were carried out under red lighting  i -_. ales o- 0 Females x upper range in males lower is zero). x i i Fig. 1. Effects of differing current (at constant voltage) on the accumulated attacking times on standard opponents generated in the shock-induced situation. between 10.30 and 16.30 h. Fig. 2 illustrates some postures seen during this form of attack. An attack was only recorded when animals actually bit or struck their opponents. Preliminary investigation revealed that mice initially respond to the electroshock by jumping, rearing against the wall of the chamber and vocalization. Behavioural measures were recorded over 10 min encounters using electro- mechanical counters (c.f. Mackintosh and Grant, 1966) or videotape tech- niques (Brain et al., 1978; Childs and Brain, 1979a, b). They include the: (a) proportion of mice evidencing overt attack; (b) latency (in seconds) from introduction of the ‘standard opponent’ to the first biting attack on that animal; (c) accumulated attacking time (AAT), i.e. the total time (in seconds) the test animal spent biting it’s opponent, and (d) number of discrete bouts of biting attack on the opponent. Attacks were separated by periods of preening, digging, cage exploration, etc. EXPERIMENT I. EFFECTS OF HOUSING CONDITION ON SHOCK-INDUCED AGGRESSION IN MALE MICE Introduction Comparisons between the shock-induced attack evident in isolated and group-housed mice have yielded conflicting data. Legrand et al. (1974) re- ported that isolated CBA/BJ mice displayed fewer upright postures and biting attacks than did group-housed counterparts, whereas Al-Maliki (1980a)  11 ig. 2. Postures employed in the shock-induced behaviour situation. (1) Both experimenta animal (right) and anosmic standard opponent (left) show upright posture in response to electroshock. (2) Experimental animal (right) socially investigates the anosmic standard opponent. (3) Experimental animal (right) attacks submissive standard opponent on delivery of shock. (4) Biting attack by experimental animal (right) on the back of the anosmic standard opponent in interval between shocks. (5) Standard opponent forced into supine position by experimental animal. (6) Mutual biting attack in ‘on shock’ situa- tion. N.B. Flattened ears and closed eyes of right hand animal. found that the converse was true of ‘TO’ strain mice. The following experi- ment was designed to compare the activities of individually-housed and group-housed mice in the shock-induced situation and to determine whether generated attack employs vulnerable loci (i.e. whether it is a defensive behav- iour) as in the case of the rat (Blanchard et al., 1977).
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