Olfactory bulbectomy: Neural structures involved in irritability and aggression in the male rat.

Performed bilateral ablations of the main olfactory bulbs of 12 male hooded rats (main OB group), of the main and accessory bulbs of 21 Ss (OB + AOB group), of the bulbs and areas caudal to the bulbs of 20 Ss (supra-OB group), and of the caudal areas only on 9 Ss (caudal group). Sham bulbectomy was performed on 7 Ss, and 8 controls were unoperated. The supra-OB and caudal groups became extremely irritable and the OB + AOB group somewhat irritable, while the main OB group was unchanged in irritability. Mouse killing increased within all groups. Postoperative irritability, but not killing, was highly correlated with extent of brain damage, while killing was correlated with irritability. It is concluded that bulbectomy-induced irritability is dependent upon damage to areas within and caudal to the bulbs to which the stria terminalis projects, and that both the irritability and killing are the result of altering a common motivational mechanism. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The hypothalamus: Neural systems involved in feeding, irritability, aggression, and copulation in male rats.

In 3 experiments with a total of 58 male hooded rats, cuts of the ventral amygdalofugal pathway resulted in slight aphagia, and cuts anterior to the medial preoptic area resulted in transient hyposexuality. A unilateral posterior medial forebrain bundle (MFB) cut combined with a contralateral parasagittal cut resulted in severe hyposexuality if the parasagittal cut lay lateral to the anterior hypothalamic nucleus, and in irritability if the parasagittal cut lay lateral to the ventromedial hypothalamic nucleus. It is concluded that (a) the medial hypothalamic nuclei exert their effects on irritability and copulation through their lateral connections with those components of the MFB that descend on, or ascend from, the lower brain stem; and (b) the neural pathways mediating the consummatory aspects of feeding, irritability, aggression, and copulation are distinct. (58 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypothalamic knife cuts: Effects on eating, drinking, irritability, aggression, and copulation in the male rat.

Describes 2 experiments with a total of 43 male hooded rats. In Exp. I, Ss with parasagittal knife cuts that separated the medial from the lateral hypothalamic areas (a) became hyperphagic, hyperdipsic, obese, and irritable; (b) did not change their level of aggressive responses against mice; and (c) copulated at an impaired rate or not at all. In Exp. II, 2 groups of Ss were subjected to coronal cuts restricted between the fornices at levels either anterior or posterior to the ventromedial hypothalamic nuclei. Most of the anterior-cut Ss increased their food and water intake, and some became irritable. Of the posterior-cut Ss, none increased and 1/2 decreased their food intake, some became hyperdipsic, and 1 became irritable. Neither of the coronal-cut groups changed levels of aggressive or sexual responses. It is concluded that the mediolateral hypothalamic connections are important for eating, irritability, and copulation. (42 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shock-elicited copulation and aggression in male rats.

Assigned 112 male Sherman naive albino rats to 12 experimental and 2 no-shock groups. Ss were presented with a receptive female, a nonreceptive female, or a male rat in a whole or 1/2 of a circular chamber. Copulatory and aggressive responses (fighting and attack) were elicited by electric shock applied to the tail. The probability of obtaining either response could be experimentally shifted by manipulating cage size, shock frequency, and sex of the stimulus animal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypothalamic and midbrain neural pathways involved in eating, drinking, irritability, aggression, and copulation in rats.

Investigated in 3 experiments with male hooded rats (N = 61) the effects of parasagittal cuts placed at 3 anterior-posterior positions. Cuts that separated portions of the medial from the lateral hypothalamus produced severe hyposexuality if they lay lateral to the medial preoptic-anterior hypothalamic continuum. Hyperphagia, irritability, and modest sexual impairment were produced if the cuts lay lateral to the anterior tips of the ventromedial hypothalamic nuclei and slightly invaded the anterior hypothalamus. Posterior, but not anterior, medial-forebrain-bundle (MFB) cuts disrupted copulation. Central gray cuts resulted in slight hyperphagia, and reticular formation cuts resulted in hyposexuality. It is concluded that the medial hypothalamic nuclei exert their effects on eating, irritability, and copulation through their lateral connections with the lateral hypothalamus and those components of the MFB that descend on (or ascend from) the lower brainstem. (40 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of nicotine deprivation and irritability on physical aggression in male smokers.

Thirty-five continuing male smokers were randomly assigned to either a deprived or a nondeprived condition. On the basis of self-reported irritability, participants were then assigned to 1 of 4 groups: deprived–high irritable, deprived–low irritable, nondeprived–high irritable, and nondeprived–low irritable. Aggression was measured with a modified version of the Taylor aggression paradigm. Self-reported smoking urge was assessed throughout the reaction time competition. Results indicated that the deprived—high irritable group displayed the highest levels of aggressive behavior. Positive associations between urge ratings and aggression indexes were detected only in the deprived—high irritable group. Results support the existence of an interactive effect of nicotine deprivation and trait irritability on physical aggression and highlight the role of smoking urge as an important factor in the deprivation-aggression link. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive functioning, irritability, and alcohol-related aggression.

The purpose of this investigation was to examine (a) whether irritability mediates the relation between executive functioning (EF) and alcohol-related aggression and (b) whether the alcohol-aggression relation is better explained by the interactive effects of EF and irritability above and beyond the effects of either variable alone. EF was measured using seven well-established neuropsychological tests. Irritability was assessed with the Caprara Irritability Scale. Participants were 313 male and female social drinkers between 21 and 35 years of age. Following the consumption of an alcohol or a placebo beverage, participants were tested on a laboratory aggression task in which electric shocks were given to and received from a fictitious opponent under the guise of a competitive reaction-time task. Aggression was operationalized as the shock intensities administered to the fictitious opponent. Results indicated that irritability successfully mediated the relation between EF and intoxicated aggression for men only. Despite the fact that irritability and EF both independently moderated the alcohol-aggression relation in previous studies, no significant interaction for their combined effect was detected here. The findings are discussed, in part, within a cognitive neoassociationistic framework for aggressive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social and developmental experience and interspecific aggression in rats.

Measured the aggressive behavior of a total of 176 male Long-Evans rats in 3 experiments. Ss raised in social isolation from weaning showed significantly more interspecific aggressive behavior than littermates raised with peers, as measured by the proportion initiating a killing attack against frogs in a 20-min arena test. Ss in 6 cross-species rearing conditions with frogs and cockroaches failed to form social attachments. When tested individually, these Ss killed the alien species as often as or more often than did controls. A significant number of adult Ss selected for nonagressive responses became killers after witnessing aggression in other Ss. (33 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The septum: Neural systems involved in eating, drinking, irritability, muricide, copulation, and activity in rats.

Measured eating, drinking, irritability, muricide, and copulation in 45 male albino Wistar rats before and after 1 of 3 coronal knife cuts in the septal region or a control operation. Activity was also measured postoperatively in the 3 experiments. Cuts posteroventral to the septum resulted in slight hypophagia, marked hyperdipsia, irritability, asexuality, and decrease in activity. Cuts of the fornix resulted only in slight decrease in activity. Cuts through the anterior septum resulted in irritability, slight hyposexuality, and slight decrease in activity. No significant correlations between the various behavioral effects were found. It is suggested that the neural pathways mediating eating, drinking, irritability, muricide, copulation, and activity are relatively distinct and that neural activity in the septal region probably does not influence behavior in any unitary fashion. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction between penile reflexes and copulation in male rats.

Placed intact, unanesthetized Long-Evans male rats in a supine position, with the penile sheath continuously retracted. Three forms of penile reflex were displayed: erections, cups, and flips. The reciprocal relation between copulation and the penile reflexes occurring in supine tests was explored in 4 experiments. In Exp I, sexual exhaustion depressed all penile reflexes, but the reflexes returned to baseline levels within 8 hrs, long before copulatory potential. In Exp II, reflexes were depressed to exhaustion levels after fewer ejaculations than were required for sexual exhaustion, an indication that reflexes are more readily evoked during copulation than in supine tests. Exp III determined that a rat's penile-reflex potential may be enhanced by placing the rat in a copulation-test cage, by allowing the male a few antecedent intromissions, or by allowing an antecedent ejaculation. The display of penile reflexes within 1 min after ejaculation suggested that the period of reduced sexual arousability following ejaculation is not due to reduced excitability in the spinal mechanisms controlling penile reflexes. In Exp IV, 1 hr of penile-reflex elicitation had no effect on subsequent copulatory behavior. Thus, sexual stimulation may increase or decrease penile-reflex potential, but a reciprocal influence was not detectable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female-enhanced aggression in male rats: Effects of genital anesthesia, castration, or preoptic lesions.

Male rats that had cohabited with ovariectomized females for 2 weeks became more aggressive toward male intruders after a novel estrous female had been placed in their home cages for a period of 4 hr on the previous day. No increase in aggression was seen in males exposed to anestrous females. Genital anesthesia did not attenuate the female-enhanced aggression effect. By contrast, no enhancement of aggression was observed in long-term castrated males after 24 hr of exposure to estrous females. Rats with bilateral electrolytic lesions in the medial preoptic area showed a normal female-enhanced aggression effect. The observations that exposure to females facilitates aggression in males subjected to genital anesthesia and in males with preoptic lesions raise the possibility that copulatory cues are not always required for the effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of olfactory stimuli during copulation in male and female rats.

Describes 3 experiments with a total of 74 gonadally-normal male and 29 ovariectomized female Long-Evans rats. Male and female reactions toward odors from novel and original partners were observed prior to the male's attaining his 1st or 2nd ejaculation. The male's reaction depended upon the sexual condition of the female. Only prior to their initial ejaculation did the males prefer their original partner's odors to those of novel females and only if the odors were collected from the females prior to copulation. This finding corresponded with observations of the male's random choice of partner during copulation. Females responded nonpreferentially if they had copulated prior to testing and showed a marked decrease in responsiveness as copulation continued. Prior to copulation females preferred the odors from males which had not copulated to those of males which had. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of alcohol on aggression in male social drinkers.

Assigned 96 male undergraduates to 1 of 8 groups in a 2 * 2 * 2 factorial design. To control fully for expectation effects, 48 Ss were led to believe that they would be drinking alcohol (vodka and tonic), and 48 believed they would be drinking only tonic water. Within each of these 2 groups, 24 Ss actually received alcohol, but 24 were given only tonic. Following the beverage administration, 48 Ss were provoked to aggress by exposing them to an insulting confederate, whereas control Ss experienced a neutral interaction. Aggression was assessed by the intensity and duration of shocks administered to the confederate on a modified version of A. H. Buss's aggression apparatus. The only significant determinant of aggression was the expectation factor: Ss who believed they had consumed alcohol were more aggressive than Ss who believed they had consumed a nonalcoholic beverage, regardless of the actual alcohol content of the drinks. Ss receiving alcohol, however, showed a significant increase in a reaction time measure, regardless of the expectation condition. Provocation to aggress was also a significant determinant of aggression, but it did not interact with the beverage conditions. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Induction of female and male mating patterns in female rats by gonadal steroids: Effects of neonatal or adult olfactory bulbectomy.

Three experiments evaluated hormonally mediated sexual response patterns in Long-Evans female rats receiving olfactory bulb ablations neonatally (Day 2) or in adulthood. In a test of Ss' reactivity to a caged male in an open field, estrogen and progesterone treatments increased the number of squares entered and the number of cage contacts, but olfactory bulb removal had no effect on these measures. During mating tests, the feminine sexual behavior of Ss' bulbectomized on Day 2 was similar to that of control-operated Ss, whereas Ss bulbectomized as adults displayed enhanced levels of lordosis, darting, and ear wiggling. Lordosis varied with estrogen dose, whereas darting was progesterone-dependent. In tests of masculine copulatory behavior, the proportion of bulbectomized Ss (Day 2 and adult) that mounted was significantly lower than that of control-operated Ss. The effects of olfactory bulb removal, which vary with the age at ablation and the behavioral system investigated, are not mediated by a single neuroendocrine system and cannot be interpreted in terms of a unitary "arousal" construct. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory repeated discrimination reversal in rats: Effects of chlordiazepoxide, dizocilpine, and morphine.

Effects of a benzodiazepine (chlordiazepoxide), an N-methyl-D-aspartate receptor antagonist (dizocilpine), and an opiate agonist (morphine) were studied with a procedure designed to assess effects of drugs and other manipulations on nonspatial learning in rats. In each session, rats were exposed to 2 different 2-choice odor-discrimination problems with food reinforcement for correct responses. One problem (performance discrimination) remained the same throughout the study. That is, 1 odor was always correct (S+) and the other was never correct (S-). For the other problem (reversal discrimination), stimuli changed every session. Six different odors were used to program the reversal discrimination; on any given session, S+ was a stimulus that had served as S- the last time it had appeared, S- was a stimulus that had been S+ on its last appearance. Thus, in each session, learning a discrimination reversal could be studied along with the performance of a comparable, but previously learned, discrimination. Chlordiazepoxide interfered with reversal learning at doses that had no effect on the performance discrimination. Morphine and dizocilpine also impaired reversal learning but only at doses that also affected performance of the well-learned performance discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of erotic stimuli on male aggression toward females.

To examine the effects of highly erotic films on aggression toward females, 72 male undergraduates were first either angered or treated in a neutral manner by a male or female confederate. After viewing a highly erotic or a neutral film, Ss were given an opportunity to both aggress against and reward the confederate. Erotic films were found to increase aggression overall, but there was no indication of differential aggression as a function of sex of target. Results for physiological arousal, however, suggested that aggression was possibly inhibited for Ss exposed to an erotic film and paired with a female. Suggestions for future lines of research based on the notion of inhibition are offered, along with observations regarding the sexual arousal and aggression relationship. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of septal lesions on inter- and intraspecies aggression in rats.

Conducted 3 experiments with septally lesioned and sham-operated male Sprague-Dawley albino rats (n = 97). Septal lesions affected shock-induced fighting, mouse killing, and fighting in a dominance situation differentially, depending on situational and temporal variables. Immediately following the lesion, preoperatively dominant Ss became submissive in a food competition test, displayed increased fighting in response to electric shock, and killed mice. 15 days after surgery, these effects on fighting behavior were no longer present. If tested for the 1st time 10-15 days after the lesion, septal Ss maintained their dominance in the food competition test, did not show an increase in shock-elicited fighting, and did not turn into "killer" rats. The effects on the muricide response were not reversible once they had been induced. (32 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory cues and movement: Stimuli mediating intraspecific aggression in the wild Norway rat.

Established male sibling pairs of laboratory-bred wild rats (R. norvegicus) in enclosures and in 4 experiments observed their aggressive, amicable, and sexual behavior following the introduction of conspecifics. Intact male Ss behaved amicably toward familiar male conspecifics, both aggressively and sexually towards unfamiliar anestrous and estrous female conspecifics, and aggressively toward unfamiliar male conspecifics. Anosmic males exhibited amicable and sexual behavior toward unfamiliar males, but did not initiate aggression toward them. The storing of a member of a resident pair in a cage with or without wood shavings, urine, and feces from a foreign colony did not affect behavior toward him by his cage mate. The storing of a foreign male in the wood shavings, urine, and feces of a colony did not affect behavior of that colony toward him. Cessation of movement on the part of an intruder of either sex inhibited attack, while immobile anesthetized male intruders elicited aggression. When presented simultaneously with moving and anesthetized intruders, resident Ss attacked only the former. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory discrimination, reversal learning, and stimulus control in rats.

Conducted 3 experiments with a total of 21 Wistar rats. In Exp I Ss were trained to discriminate lights, tones, or odors and then given a series of discrimination reversals. Only Ss trained with odors showed positive transfer on the first reversal and acquisition of a reversal set. Other experiments demonstrated that (a) Ss preferentially attended to odors when presented in compound with lights or tones; (b) odors exerted more discriminative control than tones in tests using compound stimuli of competing sign; and (c) after pretraining on the positive stimulus, acquisition of an odor but not a light discrimination occurred with virtually no errors. These results demonstrate the importance of stimulus modality in the establishment of stimulus control and the need for more careful analysis of stimulus factors in cross-species comparisons of learning ability. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)