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Handling from weaning to adulthood does not prevent hyperdefensiveness induced by septal, medial accumbens, or medial hypothalamic lesions
BEHAVIORAL AND NEURAL BIOLOGY 4 1 , 127--134
(1984)
Handling from Weaning to Adulthood Does Not Prevent Hyperdefensiveness Induced by Septal, Medial Accumbens, or Medial Hypothalamic Lesions D. J. ALBERT, M. L. WALSH, AND W . LONOLEY 1 Psychology Department, University of British Columbia, Vancouver, British Columbia V6T 1W5, Canada Weanling male hooded rats were handled or not handled for 10 min each day, 5 days/week, for 6 weeks. At the end of this time all animals received one of the following: a septal lesion, a medial accumbens lesion, a medial hypothalamic lesion, or a sham lesion. The animals were tested for defensiveness toward the experimenter on Days 3, 7, and 14 postoperatively. All behavioral testing was done blind. Each of the three lesions increased defensiveness toward the experimenter. However, with each lesion, there was no difference in the defensiveness scores of preoperatively handled and nonhandled animals at any of the postoperative test periods. The defensiveness scores of animals w~th lesions of the medial accumbens or of the septum declined over the successive postoperative test sessions while those of animals with medial hypothalamic lesions did not. These results are consistent with observations that hyperdefensiveness occurs in human subjects following tumors in each of these brain areas in spite of their familiarity with the situation in which they are observed. They contrast with observations that mouse killing induced by septal lesions is readily prevented by preoperative exposure to a mouse. I n h u m a n s u b j e c t s , t u m o r s in t h e s e p t a l r e g i o n or t h e m e d i a l h y p o t h a l a m u s r e s u l t in a h e i g h t e n e d t e n d e n c y to r e s p o n d d e f e n s i v e l y to stimuli w h i c h p r e v i o u s l y h a v e e l i c i t e d little o r no r e s p o n s e ( A l p e r s , 1937; R e e v e s & P l u m , 1969; S z a b o r & K l e i n , 1972; Z e m a n & K i n g , 1958). T h e s e o b s e r v a t i o n s h a v e a s p e c i a l s i g n i f i c a n c e b e c a u s e t h e y c o n s t i t u t e findings p a r a l l e l to t h o s e p r o d u c e d e x p e r i m e n t a l l y in a n i m a l s . In t h e rat, l e s i o n s in e i t h e r t h e s e p t u m o r t h e m e d i a l h y p o t h a l a m u s i n c r e a s e t h e t e n d e n c y to r e s p o n d d e f e n s i v e l y to stimuli p r e s e n t e d b y the e x p e r i m e n t e r ( A l b e r t , 1980; A l b e r t & B r a y l e y , 1979; A l b e r t & C h e w , 1980; A l b e r t & R i c h m o n d , 1975; A l b e r t & W a l s h , 1982; A l b e r t & W o n g , 1978a, 1978b; B r a d y & N a u t a , 1953; H a l l o n q u i s t & B r a n d e s , 1981; P a x i n o s , 1975; S c h n u r r , 1972; S e g g i e , 1968; S i n g h , 1969; T u r n e r , 1970; V e r g n e s s & K a r l i , 1970). i Supported by a grant from the National Science and Engineering Research Council of Canada. Address reprint requests to D. J. Albert. 127 0163-1047/84 $3.00 Copyright ,~ 1984 by Academic Press, Inc. A.II rights of reproduction in any form reserved.
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A characteristic of the heightened defensiveness that can be compared across species is the extent to which it is prevented by prior experience. In humans, previous experience with a situation or individual does not prevent the heightened defensiveness induced by tumors in the septal region or in the medial hypothalamus. In rats, the heightened defensiveness following lesions of the medial hypothalamus has been found to occur in spite of prior handling by the experimenter in the test situation (Albert, Walsh, Ryan, & Siemens, 1982). However, following lesions of the septal area, one experiment has found that similar experience attenuates the lesion-induced hyperdefensiveness (Albert et al., 1982) while another experiment has not (Albert, Chew, Tobani, Walsh, Lee, & Ryan, 1981). A third experiment reports that preoperative handling results only in a more rapid postoperative decline in the lesion-induced hyperdefensiveness (Kleiner, Meyer, & Meyer, 1967). These experiments have used 5- to 12-day periods of preoperative handling by the experimenter. The ambiguity in the evidence on the effect of preoperative experience on septal-lesion-induced hyperdefensiveness in rats merits further investigation. In addition, the time span over which the effects of preoperative experience have been examined in the rat are so short that it is reasonable to question whether these results can be compared to similar effects of prior experience in humans which have taken place over many years. The present experiment examined the effect of periodic handling from the time of weaning until the septal lesions were made. An extensive period of handling has the advantage that an attenuating effect of handling on defensiveness should be maximized. It is also a procedure which makes the evidence gathered with rats more comparable to the observations that have been made on humans. Because this amount of preoperative experience has not been used in previous experiments with the hyperdefensiveness induced by lesions of the medial hypothalamus, the effect of the more extensive preoperative experience was also examined with these lesions. Finally, since lesions of the medial accumbens are also known to induce hyperdefensiveness which is similar to that induced by septal or medial hypothalamic lesions, the effect of long-term handling on the defensiveness induced by medial accumbens lesions was also examined. METHOD
The subjects were 88 male hooded rats obtained from Charles River Canada. They were 25 days old at the beginning of the experiment and were housed in groups of 5 until the surgical intervention was made. After surgery the animals were housed in individual cages. Lighting in the colony was a normal 12/12h light/dark cycle with all behavioral manipulations being done during the light phase.
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Preoperative Handling Half the animals were handled for 10 min each day, 5 days each week for 6 weeks. The other animals remained in their cages during the handling period and were never touched. The handling was done in a 60 x 60 x 60-cm-high gray box, which was open at the top. The floor of the box was covered with dried corn chips (Sani-Cel). The group of five animals to be handled was placed in the box for a 10-min period. During this time the animals were repeatedly picked up, squeezed, turned on their backs, dropped onto the floor, stroked, and the like. At times the animals would be handled gently and other times somewhat roughly. The intent was to expose the animals to the kind of handling that they would be subjected to during postoperative defensiveness testing.
Surgery At the end of the 6-week period of preoperative handling, both the handled and nonhandled rats were anesthetized with sodium pentobarbital anesthesia. With the aid of a Kopf stereotaxic instrument and a stainlesssteel electrode (anode) insulated to within 0.25 mm of the tip, bilateral lesions were made in the lateral septum, medial accumbens, or medial hypothalamus, or the animals were given a sham lesion. Half of the handled and nonhandled animals were each randomly assigned to the lesion groups. The coordinates for the lesions were as follows: lateral septum, 2.0 mm anterior to bregma, 0.7 mm lateral to the midline, and 5.5 mm ventral to the cortical surface (2.0 mA, 40 sec); medial accumbens, 2.9 mm anterior, 1.0 mm lateral, and 7.0 mm ventral to the cortical surface (2.0 mA, 21 sec); medial hypothalamus, 0.0 mm anterior, 0.7 mm lateral, and 9.0 mm ventral (2.0 mA, 17 sec; in all cases the mouth bar was 5.0 mm above the level of the interaural line). Sham lesions involved making a hole in the skull at one of the appropriate locations but the electrodes were not lowered into the brain. Following surgery, a small amount of antibiotic was sprinkled around the wound, the incision was closed, and the animal was returned to an individual living cage.
Behavioral Testing Defensiveness toward the experimenter was tested in the same box that the animals had been handled in and by an individual who had done part of the handling. The testing was done on Days 3, 7, and 14 postoperatively. The blind testing procedure used was such that the observer knew neither the group to which an animal belonged nor its previous test scores. The same observer did all behavioral testing. Defensiveness was assessed using a behavioral rating scale which we
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formerly regarded as a measure of reactivity but which now seems more correctly regarded as a measure of defensiveness (Albert & Chew, 1980; Albert & Walsh, 1982, 1984). The animal was taken from its living cage and placed by itself in the arena used for preoperative handling. After a 5-min habituation period, the animal was exposed to the following series of stimuli and its defensive behavior was scored on a scale of 0 to 3, 0 corresponding to little or no response and 3 indicating a defensive attack. In addition, the animal was scored from 0 to 3 on both the amount of biting and amount of vocalization emitted throughout the testing period. The stimuli used were as follows: a pencil held in front of the nose, a tap on the back with a pencil, a gloved hand placed in front of the nose, a poke in the side with a stick, holding by the tail, and grasping around the abdomen. The maximum score on this scale is 24. This scale has been described in more detail in some previous experiments (Albert & Brayley, 1979; Albert & Richmond, 1975, 1976).
Histology Following behavioral testing, each animal was sacrificed, and its brain was immediately removed and placed in formal-saline. The brains were later sectioned in a cryostat and stained with cresyl violet.
RESULTS Lesions of the septum, medial accumbens, and medial hypothalamus each increased defensiveness toward the experimenter significantly above the level of the sham-lesioned animals on the Day 3 test (Dunnett's test, all p's < .02; Fig. 1). Preoperative handling did not significantly attenuate the defensiveness induced by any of the three lesions on the first test day (F(1, 81) = .41; p > .50; individual comparisons with t tests for independent samples, all p's > .50). It is, nevertheless, noteworthy that the defensiveness scores of each of the preoperatively handled groups were slightly lower than those of its nonhandled counterpart. The number of subjects in each group were septal lesion, handled--11, nonhandled-12; medial accumbens lesion, handled--10, nonhandled--9 medial hypothalamic lesions, handled--12, nonhandled--14; sham, handled--10, nonhandled--10. The standard error of the mean defensiveness scores were reasonably consistent over days for the lesioned and sham-lesioned groups (average value over all days: lesioned groups, 1.6; sham-lesions, O.7). On the Day 7 test, the defensiveness scores of the corresponding handled and nonhandled groups again did not differ significantly (t tests, all p's > .10). Further, all groups, except for the handled animals with septal lesions, had defensiveness scores significantly higher than their corresponding sham-lesioned control group (Dunnett's test, all p's < .05).
HYPERDEFENSIVENESS
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On the Day 14 test, the defensiveness scores of the corresponding handled and nonhandled groups still did not differ in any case (t tests, all p's > .20). Only the defensiveness scores of the animals with medial hypothalamic lesions and the nonhandled animals with medial accumbens lesions were significantly greater than those of their sham-operated control group (Dunnett's test, all p's < .05). The overall analysis of variance produced a significant interaction between lesions and test days (F(6, 160) = 16.3, p < .01). Individual paired comparisons between Day 3 and Day 14 tests indicated that the defensiveness scores of the rats with medial accumbens or septal lesions (t tests, all p's < .01) but not those with medial hypothalamic or sham lesions declined significantly over this time period (t tests, all p's > .30). Examination of the histological material revealed lesions that were slightly smaller but similar in location to those whose effects have been described in a number of recent reports (Albert & Brayley, 1979; Albert et al., 1982; Albert, Walsh, & White, 1984). One or two of the animals in each group had lesions which might have lead to their exclusion if precise anatomical criteria for the lesions had been used. However. since the number of animals in this category was small and since such animals were present in each of the lesion groups, the data of no animals were discarded. The septal lesions destroyed the entire medial and lateral septal nuclei except for the most rostral and caudal portions. The fornix was spared in most cases. The lesions of the medial accumbens destroyed a substantial portion of the tissue between the rostral arm of the anterior
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ALBERT, WALSH, AND LONGLEY
commissure and the vertical limb of the diagonal band of Broca. There was usually some damage to the ventrolateral edge of the lateral septum. The lesions of the medial hypothalamus destroyed most of tissue in the ventromedial hypothalamus between the third ventricle and a vertical line through the fornix at the level of the ventromedial nucleus.
DISCUSSION A long period of preoperative experience with the experimenter and with the testing situation does not prevent the hyperdefensiveness toward the experimenter induced by lesions of the septum, medial accumbens, or medial hypothalamus in rats. This finding was obtained in spite of the fact that the period of exposure to the experimenter included the period when the rats were very young and that the preoperative handling was done in the very same situation where defensiveness was assessed postoperatively. These results extend those we have obtained previously with medial accumbens and medial hypothalamic lesions in which the period of handling was done for only a 5- to 7-day period just prior to surgery in adult animals (Albert et al., 1981, 1982). The decline in defensiveness scores over days in rats with medial accumbens but not medial hypothalamic lesions is consistent with previous observations (Albert & Brayley, 1979; Albert et al., 1981; Albert & Chew, 1980; Albert & Richmond, 1975, 1976; Albert et al., 1982; Singh, 1969; however, see also Hallonquist & Brandes, 1981). The absence of an attenuation of septal-lesion-induced hyperdefensiveness in the present experiment is surprising. Since previous evidence was split in indicating that preoperative handling did attenuate the lesioninduced hyperdefensiveness in one experiment (Albert et al., 1982) and caused a more rapid postoperative decline in hyperdefensiveness in another (Kleiner et al., 1967), it seemed reasonable to suppose that the much longer period of handling of the present experiment would result in an attenuation. Since the present observations were done using a blind procedure in which the observer was aware of neither the lesion nor previous test scores, the present results must be considered the most rigorously obtained of those presently available. Clearly, it can be inferred from these results that preoperative handling in septal-lesioned rats can produce at most an attenuation, and not a total elimination, of septallesion-induced hyperdefensiveness. The observation that the defensiveness scores decline progressively over test sessions is consistent with numerous previous observations of septal-lesioned animals (Albert & Brayley, 1979; Albert & Richmond, 1975, 1976; Albert & Walsh, 1982; Brady & Nauta, 1953; Hallonquist & Brandes, 1981; Singh, 1969). Two important conclusions are supported by the present results. First, the failure of long-term preoperative experience to block the hyperdefensiveness induced by lesions in the septum, medial accumbens, or
HYPERDEFENSIVENESS
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medial hypothalamus in rats serves to relate the results obtained from animal studies to the little evidence available from naturally occurring damage to these regions in humans. Tumors in each of these areas in humans have served to heighten defensiveness in spite of the lengthy experience the human patients had with the individuals in their environment (Alpers, 1937; Reeves & Plum, 1969; Zeman & King, 1958). We have argued previously that the most obvious manifestation of the heightened defensiveness in both humans and rats is in an increased tendency to respond defensively to stimuli which they would previously have treated as neutral (Albert & Walsh, 1982, 1984). The second important consequence of the present experiment is to further distinguish between the mouse killing and hyperdefensiveness induced by septal lesions in rats. The present experiment aids in making this distinction because while preoperative experience, even from weaning, does not eliminate the lesion-induced hyperdefensiveness, much shorter periods of preoperative exposure to a mouse are sufficient to completely prevent the septal-lesion-induced mouse killing. The latter effect has been demonstrated with preoperative exposure periods as short as 5 days (Albert et al., 1982, 1984). These observations reinforce the conclusions drawn from microinjection studies that the effects of these lesions on mouse killing and reactivity are experimentally separable and dependent on different neural circuitry (Albert & Wong, 1978a, 1978b). They also reinforce other arguments that it is the lesion-induced increase in defensiveness of the septal-lesioned animals that is most directly relevant to human behavior and not the mouse killing as is sometimes suggested (Atkinson, Atkinson, & Hilgard, 1983; McFarland, 1981; Samuel, 1975).
REFERENCES Albert, D. J. (1980). Hyperreactivity following temporary chemical lesions in the region
ventral to the anterior septum but not in the anterior olfactory nucleus, the lateral olfactory tract or the olfactory bulb. Physiology and Behavior, 25, 481-483. Albert, D. J., & Brayley, K. N. (1979). Mouse kilhng and hyperreactivity followinglesions of the medial hypothalamus, the lateral septum, the bed nucleus of the stria terminalis. or the region ventral to the anterior septum. Physiology and Behavior, 23, 439-443. Albert, D. J. & Chew. G. L. (1980). The septal forebrain and the inhibitory modulation of attack and defense in the rat: A review. Behavioral and Neural Biology, 3, 357388. Albert, D. J., Chew. G. L., Tobani, A., Walsh, M. L., Lee, C. Y. S., and Ryan, J. (1981). Preoperative gentlingdoes not attenuate septal-lesionreducedhyperreactivity.Physiology and Behavior. 27, 387-389. Albert, D. J., & Richmond, S. E., (1975). Septal hyperreactivity: A comparison of lesions within and adjacent to the septum. Phystology and Behavior, 15, 339-347. Albert, D, J., & Richmond, S. E. (1976). Neural pathways mediating septal hyperreactivity. Physiology and Behavior, 17, 451-455. Albert, D. J., & Walsh, M. L. (1982). The inhibitory modulation of agonistic behavior in the rat brain: A review. Neuroscience and Biobehavioral Reviews, 6, 125-143. Albert, D. J., & Walsh, M. L. (1984). Neural systems and the inhibitory modulation of
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ALBERT, WALSH, AND LONGLEY agonistic behavior: A comparison of mammalian species. Neuroscience and Biobehavioral
Reviews, in press. Albert, D. J., Walsh, M. L., Ryan, J., & Siemens, Y. (1982). A comparison of the effect of preoperative gentling on the mouse killing and reactivity induced by lesions of the lateral septum, the medial accumbens nucleus, and the medial hypothalamus. Physiology and Behavior, 28, 1117-1120. Albert, D. J., Walsh, M. L., & White, R. (1984). Rearing rats with mice prevents induction of mouse killing by lesions of the septum but not lesions of the medial hypothalamus or medial accumbens. Physiology and Behavior, 32, 143-145. Albert, D. J., & Wong, R. C. K. (1978a). Hyperreactivity, muricide, and intraspecific aggression in the rat produced by infusion of local anesthetic into the lateral septum or surrounding areas. Journal of Comparative and Physiological Psychology, 92, 10621073. Albert, D. J. & Wong, R. C. K. (1978b). Interanimal aggression and hyperreactivity following hypothalamic infusion of local anesthetic in the rat. Physiology and Behavior, 20, 755-761. Alpers, B. J. (1937). Relation of the hypothalamus to disorders of personality. Archives of Neurology and Psychiatry, 38, 291-303. Atkinson, R. L., Atkinson, R. C., & Hilgard, E. R. (1983). Introduction to Psychology, 8th ed. New York: Harcourt Brace Jovanovich. Brady, J. V., & Nanta, W. J. H. (1953). Subcortical mechanisms in emotional behavior: Affective changes following septal forebrain lesions in the albino rat. Journal of Comparative and Physiological Psychology, 46, 339-345. Hallonquist, J. D., & Brandes, J. S. (1981). Housing affects hyperreactivity but not obesity induced by medial hypothalamic lesions. Physiology and Behavior, 26, 1025-1029. Kleiner, F. B., Meyer, P. M., & Meyer, D. R. (1967). Effects of simultaneous septal and amygdaloid lesions upon emotionality and retention of a black-white discrimination. Brain Research, 5, 459-468. McFarland, R. A. (1981). Physiological Psychology. The Biology of Human Behavior. Palo Alto, CA. Mayfield. Paxinos, G. (1975). The septum: Neural systems involved in eating, drinking, irritability, muricide, copulation, and activity in rats. Journal of Comparative and Physiological Psychology, 89,1154-1168. Reeves, G. A., & Plum, F. (1969). Hyperphagia, rage, and dementia accompanying a ventromedial hypothalamic neoplasm. Archives of Neurology, 20, 616-624. Samuel, W. (1975). Contemporary Social Psychology: An Introduction. Englewood Cliffs, NJ: Prentice-Hall. Schnurr, R. (1972). Localization of the septal rage syndrome in Long-Evans rats. Journal of Comparative and Physiological Psychology, 81, 291-296. Seggie, J. (1968). Effect of somatosensory stimulation on affective behavior of septal rats. Journal of Comparative and Physiological Psychology, 66, 820-822. Singh, D. (1969). Comparison of hyperemotionality caused by lesions in the septal and ventromedial hypothalamic areas. Psychonomic Science, 16, 3-4. Szabor, A., & Klein, M. (1972). Clinical features and treatment of abnormal patterns of affective behaviour associated with hypothalamic lesions. Therapia Hungarica, 20, 3-9. Turner, B. H. (1970). Neural structures involved in the rage syndrome of the rat. Journal of Comparative and Physiological Psychology, 71, 103-113. Vergnes, M., & Karli, P. (1970). Declenchement d'un comportement d'agression par stimulation electrique de l'hypothalamus median chez le rat. Physiology and Behavior, 5, 1427-1430. Zeman, W., & King, F. A. (1958). Tumors of the septum pellucidum and adjacent structures with abnormal affective behavior: An anterior midline structure syndrome. Journal of Nervous and Mental Disease. 127, 490-502.
(1984)
Handling from Weaning to Adulthood Does Not Prevent Hyperdefensiveness Induced by Septal, Medial Accumbens, or Medial Hypothalamic Lesions D. J. ALBERT, M. L. WALSH, AND W . LONOLEY 1 Psychology Department, University of British Columbia, Vancouver, British Columbia V6T 1W5, Canada Weanling male hooded rats were handled or not handled for 10 min each day, 5 days/week, for 6 weeks. At the end of this time all animals received one of the following: a septal lesion, a medial accumbens lesion, a medial hypothalamic lesion, or a sham lesion. The animals were tested for defensiveness toward the experimenter on Days 3, 7, and 14 postoperatively. All behavioral testing was done blind. Each of the three lesions increased defensiveness toward the experimenter. However, with each lesion, there was no difference in the defensiveness scores of preoperatively handled and nonhandled animals at any of the postoperative test periods. The defensiveness scores of animals w~th lesions of the medial accumbens or of the septum declined over the successive postoperative test sessions while those of animals with medial hypothalamic lesions did not. These results are consistent with observations that hyperdefensiveness occurs in human subjects following tumors in each of these brain areas in spite of their familiarity with the situation in which they are observed. They contrast with observations that mouse killing induced by septal lesions is readily prevented by preoperative exposure to a mouse. I n h u m a n s u b j e c t s , t u m o r s in t h e s e p t a l r e g i o n or t h e m e d i a l h y p o t h a l a m u s r e s u l t in a h e i g h t e n e d t e n d e n c y to r e s p o n d d e f e n s i v e l y to stimuli w h i c h p r e v i o u s l y h a v e e l i c i t e d little o r no r e s p o n s e ( A l p e r s , 1937; R e e v e s & P l u m , 1969; S z a b o r & K l e i n , 1972; Z e m a n & K i n g , 1958). T h e s e o b s e r v a t i o n s h a v e a s p e c i a l s i g n i f i c a n c e b e c a u s e t h e y c o n s t i t u t e findings p a r a l l e l to t h o s e p r o d u c e d e x p e r i m e n t a l l y in a n i m a l s . In t h e rat, l e s i o n s in e i t h e r t h e s e p t u m o r t h e m e d i a l h y p o t h a l a m u s i n c r e a s e t h e t e n d e n c y to r e s p o n d d e f e n s i v e l y to stimuli p r e s e n t e d b y the e x p e r i m e n t e r ( A l b e r t , 1980; A l b e r t & B r a y l e y , 1979; A l b e r t & C h e w , 1980; A l b e r t & R i c h m o n d , 1975; A l b e r t & W a l s h , 1982; A l b e r t & W o n g , 1978a, 1978b; B r a d y & N a u t a , 1953; H a l l o n q u i s t & B r a n d e s , 1981; P a x i n o s , 1975; S c h n u r r , 1972; S e g g i e , 1968; S i n g h , 1969; T u r n e r , 1970; V e r g n e s s & K a r l i , 1970). i Supported by a grant from the National Science and Engineering Research Council of Canada. Address reprint requests to D. J. Albert. 127 0163-1047/84 $3.00 Copyright ,~ 1984 by Academic Press, Inc. A.II rights of reproduction in any form reserved.
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A characteristic of the heightened defensiveness that can be compared across species is the extent to which it is prevented by prior experience. In humans, previous experience with a situation or individual does not prevent the heightened defensiveness induced by tumors in the septal region or in the medial hypothalamus. In rats, the heightened defensiveness following lesions of the medial hypothalamus has been found to occur in spite of prior handling by the experimenter in the test situation (Albert, Walsh, Ryan, & Siemens, 1982). However, following lesions of the septal area, one experiment has found that similar experience attenuates the lesion-induced hyperdefensiveness (Albert et al., 1982) while another experiment has not (Albert, Chew, Tobani, Walsh, Lee, & Ryan, 1981). A third experiment reports that preoperative handling results only in a more rapid postoperative decline in the lesion-induced hyperdefensiveness (Kleiner, Meyer, & Meyer, 1967). These experiments have used 5- to 12-day periods of preoperative handling by the experimenter. The ambiguity in the evidence on the effect of preoperative experience on septal-lesion-induced hyperdefensiveness in rats merits further investigation. In addition, the time span over which the effects of preoperative experience have been examined in the rat are so short that it is reasonable to question whether these results can be compared to similar effects of prior experience in humans which have taken place over many years. The present experiment examined the effect of periodic handling from the time of weaning until the septal lesions were made. An extensive period of handling has the advantage that an attenuating effect of handling on defensiveness should be maximized. It is also a procedure which makes the evidence gathered with rats more comparable to the observations that have been made on humans. Because this amount of preoperative experience has not been used in previous experiments with the hyperdefensiveness induced by lesions of the medial hypothalamus, the effect of the more extensive preoperative experience was also examined with these lesions. Finally, since lesions of the medial accumbens are also known to induce hyperdefensiveness which is similar to that induced by septal or medial hypothalamic lesions, the effect of long-term handling on the defensiveness induced by medial accumbens lesions was also examined. METHOD
The subjects were 88 male hooded rats obtained from Charles River Canada. They were 25 days old at the beginning of the experiment and were housed in groups of 5 until the surgical intervention was made. After surgery the animals were housed in individual cages. Lighting in the colony was a normal 12/12h light/dark cycle with all behavioral manipulations being done during the light phase.
HYPERDEFENSIVENESS
129
Preoperative Handling Half the animals were handled for 10 min each day, 5 days each week for 6 weeks. The other animals remained in their cages during the handling period and were never touched. The handling was done in a 60 x 60 x 60-cm-high gray box, which was open at the top. The floor of the box was covered with dried corn chips (Sani-Cel). The group of five animals to be handled was placed in the box for a 10-min period. During this time the animals were repeatedly picked up, squeezed, turned on their backs, dropped onto the floor, stroked, and the like. At times the animals would be handled gently and other times somewhat roughly. The intent was to expose the animals to the kind of handling that they would be subjected to during postoperative defensiveness testing.
Surgery At the end of the 6-week period of preoperative handling, both the handled and nonhandled rats were anesthetized with sodium pentobarbital anesthesia. With the aid of a Kopf stereotaxic instrument and a stainlesssteel electrode (anode) insulated to within 0.25 mm of the tip, bilateral lesions were made in the lateral septum, medial accumbens, or medial hypothalamus, or the animals were given a sham lesion. Half of the handled and nonhandled animals were each randomly assigned to the lesion groups. The coordinates for the lesions were as follows: lateral septum, 2.0 mm anterior to bregma, 0.7 mm lateral to the midline, and 5.5 mm ventral to the cortical surface (2.0 mA, 40 sec); medial accumbens, 2.9 mm anterior, 1.0 mm lateral, and 7.0 mm ventral to the cortical surface (2.0 mA, 21 sec); medial hypothalamus, 0.0 mm anterior, 0.7 mm lateral, and 9.0 mm ventral (2.0 mA, 17 sec; in all cases the mouth bar was 5.0 mm above the level of the interaural line). Sham lesions involved making a hole in the skull at one of the appropriate locations but the electrodes were not lowered into the brain. Following surgery, a small amount of antibiotic was sprinkled around the wound, the incision was closed, and the animal was returned to an individual living cage.
Behavioral Testing Defensiveness toward the experimenter was tested in the same box that the animals had been handled in and by an individual who had done part of the handling. The testing was done on Days 3, 7, and 14 postoperatively. The blind testing procedure used was such that the observer knew neither the group to which an animal belonged nor its previous test scores. The same observer did all behavioral testing. Defensiveness was assessed using a behavioral rating scale which we
130
ALBERT, WALSH, AND LONGLEY
formerly regarded as a measure of reactivity but which now seems more correctly regarded as a measure of defensiveness (Albert & Chew, 1980; Albert & Walsh, 1982, 1984). The animal was taken from its living cage and placed by itself in the arena used for preoperative handling. After a 5-min habituation period, the animal was exposed to the following series of stimuli and its defensive behavior was scored on a scale of 0 to 3, 0 corresponding to little or no response and 3 indicating a defensive attack. In addition, the animal was scored from 0 to 3 on both the amount of biting and amount of vocalization emitted throughout the testing period. The stimuli used were as follows: a pencil held in front of the nose, a tap on the back with a pencil, a gloved hand placed in front of the nose, a poke in the side with a stick, holding by the tail, and grasping around the abdomen. The maximum score on this scale is 24. This scale has been described in more detail in some previous experiments (Albert & Brayley, 1979; Albert & Richmond, 1975, 1976).
Histology Following behavioral testing, each animal was sacrificed, and its brain was immediately removed and placed in formal-saline. The brains were later sectioned in a cryostat and stained with cresyl violet.
RESULTS Lesions of the septum, medial accumbens, and medial hypothalamus each increased defensiveness toward the experimenter significantly above the level of the sham-lesioned animals on the Day 3 test (Dunnett's test, all p's < .02; Fig. 1). Preoperative handling did not significantly attenuate the defensiveness induced by any of the three lesions on the first test day (F(1, 81) = .41; p > .50; individual comparisons with t tests for independent samples, all p's > .50). It is, nevertheless, noteworthy that the defensiveness scores of each of the preoperatively handled groups were slightly lower than those of its nonhandled counterpart. The number of subjects in each group were septal lesion, handled--11, nonhandled-12; medial accumbens lesion, handled--10, nonhandled--9 medial hypothalamic lesions, handled--12, nonhandled--14; sham, handled--10, nonhandled--10. The standard error of the mean defensiveness scores were reasonably consistent over days for the lesioned and sham-lesioned groups (average value over all days: lesioned groups, 1.6; sham-lesions, O.7). On the Day 7 test, the defensiveness scores of the corresponding handled and nonhandled groups again did not differ significantly (t tests, all p's > .10). Further, all groups, except for the handled animals with septal lesions, had defensiveness scores significantly higher than their corresponding sham-lesioned control group (Dunnett's test, all p's < .05).
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On the Day 14 test, the defensiveness scores of the corresponding handled and nonhandled groups still did not differ in any case (t tests, all p's > .20). Only the defensiveness scores of the animals with medial hypothalamic lesions and the nonhandled animals with medial accumbens lesions were significantly greater than those of their sham-operated control group (Dunnett's test, all p's < .05). The overall analysis of variance produced a significant interaction between lesions and test days (F(6, 160) = 16.3, p < .01). Individual paired comparisons between Day 3 and Day 14 tests indicated that the defensiveness scores of the rats with medial accumbens or septal lesions (t tests, all p's < .01) but not those with medial hypothalamic or sham lesions declined significantly over this time period (t tests, all p's > .30). Examination of the histological material revealed lesions that were slightly smaller but similar in location to those whose effects have been described in a number of recent reports (Albert & Brayley, 1979; Albert et al., 1982; Albert, Walsh, & White, 1984). One or two of the animals in each group had lesions which might have lead to their exclusion if precise anatomical criteria for the lesions had been used. However. since the number of animals in this category was small and since such animals were present in each of the lesion groups, the data of no animals were discarded. The septal lesions destroyed the entire medial and lateral septal nuclei except for the most rostral and caudal portions. The fornix was spared in most cases. The lesions of the medial accumbens destroyed a substantial portion of the tissue between the rostral arm of the anterior
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commissure and the vertical limb of the diagonal band of Broca. There was usually some damage to the ventrolateral edge of the lateral septum. The lesions of the medial hypothalamus destroyed most of tissue in the ventromedial hypothalamus between the third ventricle and a vertical line through the fornix at the level of the ventromedial nucleus.
DISCUSSION A long period of preoperative experience with the experimenter and with the testing situation does not prevent the hyperdefensiveness toward the experimenter induced by lesions of the septum, medial accumbens, or medial hypothalamus in rats. This finding was obtained in spite of the fact that the period of exposure to the experimenter included the period when the rats were very young and that the preoperative handling was done in the very same situation where defensiveness was assessed postoperatively. These results extend those we have obtained previously with medial accumbens and medial hypothalamic lesions in which the period of handling was done for only a 5- to 7-day period just prior to surgery in adult animals (Albert et al., 1981, 1982). The decline in defensiveness scores over days in rats with medial accumbens but not medial hypothalamic lesions is consistent with previous observations (Albert & Brayley, 1979; Albert et al., 1981; Albert & Chew, 1980; Albert & Richmond, 1975, 1976; Albert et al., 1982; Singh, 1969; however, see also Hallonquist & Brandes, 1981). The absence of an attenuation of septal-lesion-induced hyperdefensiveness in the present experiment is surprising. Since previous evidence was split in indicating that preoperative handling did attenuate the lesioninduced hyperdefensiveness in one experiment (Albert et al., 1982) and caused a more rapid postoperative decline in hyperdefensiveness in another (Kleiner et al., 1967), it seemed reasonable to suppose that the much longer period of handling of the present experiment would result in an attenuation. Since the present observations were done using a blind procedure in which the observer was aware of neither the lesion nor previous test scores, the present results must be considered the most rigorously obtained of those presently available. Clearly, it can be inferred from these results that preoperative handling in septal-lesioned rats can produce at most an attenuation, and not a total elimination, of septallesion-induced hyperdefensiveness. The observation that the defensiveness scores decline progressively over test sessions is consistent with numerous previous observations of septal-lesioned animals (Albert & Brayley, 1979; Albert & Richmond, 1975, 1976; Albert & Walsh, 1982; Brady & Nauta, 1953; Hallonquist & Brandes, 1981; Singh, 1969). Two important conclusions are supported by the present results. First, the failure of long-term preoperative experience to block the hyperdefensiveness induced by lesions in the septum, medial accumbens, or
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medial hypothalamus in rats serves to relate the results obtained from animal studies to the little evidence available from naturally occurring damage to these regions in humans. Tumors in each of these areas in humans have served to heighten defensiveness in spite of the lengthy experience the human patients had with the individuals in their environment (Alpers, 1937; Reeves & Plum, 1969; Zeman & King, 1958). We have argued previously that the most obvious manifestation of the heightened defensiveness in both humans and rats is in an increased tendency to respond defensively to stimuli which they would previously have treated as neutral (Albert & Walsh, 1982, 1984). The second important consequence of the present experiment is to further distinguish between the mouse killing and hyperdefensiveness induced by septal lesions in rats. The present experiment aids in making this distinction because while preoperative experience, even from weaning, does not eliminate the lesion-induced hyperdefensiveness, much shorter periods of preoperative exposure to a mouse are sufficient to completely prevent the septal-lesion-induced mouse killing. The latter effect has been demonstrated with preoperative exposure periods as short as 5 days (Albert et al., 1982, 1984). These observations reinforce the conclusions drawn from microinjection studies that the effects of these lesions on mouse killing and reactivity are experimentally separable and dependent on different neural circuitry (Albert & Wong, 1978a, 1978b). They also reinforce other arguments that it is the lesion-induced increase in defensiveness of the septal-lesioned animals that is most directly relevant to human behavior and not the mouse killing as is sometimes suggested (Atkinson, Atkinson, & Hilgard, 1983; McFarland, 1981; Samuel, 1975).
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ventral to the anterior septum but not in the anterior olfactory nucleus, the lateral olfactory tract or the olfactory bulb. Physiology and Behavior, 25, 481-483. Albert, D. J., & Brayley, K. N. (1979). Mouse kilhng and hyperreactivity followinglesions of the medial hypothalamus, the lateral septum, the bed nucleus of the stria terminalis. or the region ventral to the anterior septum. Physiology and Behavior, 23, 439-443. Albert, D. J. & Chew. G. L. (1980). The septal forebrain and the inhibitory modulation of attack and defense in the rat: A review. Behavioral and Neural Biology, 3, 357388. Albert, D. J., Chew. G. L., Tobani, A., Walsh, M. L., Lee, C. Y. S., and Ryan, J. (1981). Preoperative gentlingdoes not attenuate septal-lesionreducedhyperreactivity.Physiology and Behavior. 27, 387-389. Albert, D. J., & Richmond, S. E., (1975). Septal hyperreactivity: A comparison of lesions within and adjacent to the septum. Phystology and Behavior, 15, 339-347. Albert, D, J., & Richmond, S. E. (1976). Neural pathways mediating septal hyperreactivity. Physiology and Behavior, 17, 451-455. Albert, D. J., & Walsh, M. L. (1982). The inhibitory modulation of agonistic behavior in the rat brain: A review. Neuroscience and Biobehavioral Reviews, 6, 125-143. Albert, D. J., & Walsh, M. L. (1984). Neural systems and the inhibitory modulation of
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ALBERT, WALSH, AND LONGLEY agonistic behavior: A comparison of mammalian species. Neuroscience and Biobehavioral
Reviews, in press. Albert, D. J., Walsh, M. L., Ryan, J., & Siemens, Y. (1982). A comparison of the effect of preoperative gentling on the mouse killing and reactivity induced by lesions of the lateral septum, the medial accumbens nucleus, and the medial hypothalamus. Physiology and Behavior, 28, 1117-1120. Albert, D. J., Walsh, M. L., & White, R. (1984). Rearing rats with mice prevents induction of mouse killing by lesions of the septum but not lesions of the medial hypothalamus or medial accumbens. Physiology and Behavior, 32, 143-145. Albert, D. J., & Wong, R. C. K. (1978a). Hyperreactivity, muricide, and intraspecific aggression in the rat produced by infusion of local anesthetic into the lateral septum or surrounding areas. Journal of Comparative and Physiological Psychology, 92, 10621073. Albert, D. J. & Wong, R. C. K. (1978b). Interanimal aggression and hyperreactivity following hypothalamic infusion of local anesthetic in the rat. Physiology and Behavior, 20, 755-761. Alpers, B. J. (1937). Relation of the hypothalamus to disorders of personality. Archives of Neurology and Psychiatry, 38, 291-303. Atkinson, R. L., Atkinson, R. C., & Hilgard, E. R. (1983). Introduction to Psychology, 8th ed. New York: Harcourt Brace Jovanovich. Brady, J. V., & Nanta, W. J. H. (1953). Subcortical mechanisms in emotional behavior: Affective changes following septal forebrain lesions in the albino rat. Journal of Comparative and Physiological Psychology, 46, 339-345. Hallonquist, J. D., & Brandes, J. S. (1981). Housing affects hyperreactivity but not obesity induced by medial hypothalamic lesions. Physiology and Behavior, 26, 1025-1029. Kleiner, F. B., Meyer, P. M., & Meyer, D. R. (1967). Effects of simultaneous septal and amygdaloid lesions upon emotionality and retention of a black-white discrimination. Brain Research, 5, 459-468. McFarland, R. A. (1981). Physiological Psychology. The Biology of Human Behavior. Palo Alto, CA. Mayfield. Paxinos, G. (1975). The septum: Neural systems involved in eating, drinking, irritability, muricide, copulation, and activity in rats. Journal of Comparative and Physiological Psychology, 89,1154-1168. Reeves, G. A., & Plum, F. (1969). Hyperphagia, rage, and dementia accompanying a ventromedial hypothalamic neoplasm. Archives of Neurology, 20, 616-624. Samuel, W. (1975). Contemporary Social Psychology: An Introduction. Englewood Cliffs, NJ: Prentice-Hall. Schnurr, R. (1972). Localization of the septal rage syndrome in Long-Evans rats. Journal of Comparative and Physiological Psychology, 81, 291-296. Seggie, J. (1968). Effect of somatosensory stimulation on affective behavior of septal rats. Journal of Comparative and Physiological Psychology, 66, 820-822. Singh, D. (1969). Comparison of hyperemotionality caused by lesions in the septal and ventromedial hypothalamic areas. Psychonomic Science, 16, 3-4. Szabor, A., & Klein, M. (1972). Clinical features and treatment of abnormal patterns of affective behaviour associated with hypothalamic lesions. Therapia Hungarica, 20, 3-9. Turner, B. H. (1970). Neural structures involved in the rage syndrome of the rat. Journal of Comparative and Physiological Psychology, 71, 103-113. Vergnes, M., & Karli, P. (1970). Declenchement d'un comportement d'agression par stimulation electrique de l'hypothalamus median chez le rat. Physiology and Behavior, 5, 1427-1430. Zeman, W., & King, F. A. (1958). Tumors of the septum pellucidum and adjacent structures with abnormal affective behavior: An anterior midline structure syndrome. Journal of Nervous and Mental Disease. 127, 490-502.