Regulation Of Aggressive Behavior Research Articles

Spring and Autumn Territoriality in Song Sparrows: Same Behavior, Different Mechanisms?

Vertebrates show a diverse array of social behaviors associated with territoriality. Field and laboratory experiments indicate that underlying themes-including mechanisms-may exist. For example in birds, extensive evidence over many decades has implicated a role for testosterone in the activation of territorial aggression in reproductive contexts. Territoriality at other times of the year appeared to be independent of gonadal hormone control. One obvious question is-why this diversity of control mechanisms for an apparently similar behavior? Control of testosterone secretion during the breeding season must balance the need to compete with other males (that tends to increase testosterone secretion), and the need to provide parental care (that requires lower testosterone concentrations). Regulation of aggressive behaviors by testosterone in the non-breeding season may incur substantial costs. A series of experiments on the male song sparrow, Melospiza melodia morphna, of western Washington State have revealed possible mechanisms to avoid these costs. Song sparrows are sedentary and defend territories in both breeding and non-breeding seasons. Dominance interactions, territorial aggression and song during the non-breeding season are essentially identical to those during the breeding season. Although in the non-breeding season plasma testosterone and estradiol levels are very low, treatment with an aromatase inhibitor decreases aggression and simultaneous implantation of estradiol restores territorial behavior. These data suggest that the mechanism by which testosterone regulates territorial behavior at the neural level remains intact throughout the year. How the hormonal message to activate such behavior gets to the brain in different season does, however, appear to be different.

Co-localization of NK1-receptor mRNA with glutamate immunopositivity in cat hypothalamic neurons by the combination of in situ hybridization and immunohistochemistry

Previous studies had demonstrated that, in the cat, aggression is mediated by glutamatergic neurons in the anterior medial hypothalamus which project to the periaqueductal gray. Additionally, NK1 receptor activation in the medial hypothalamus plays a role in the regulation of aggressive behavior by the medial amygdala. In the present study, in situ hybridization and immunohistochemistry were combined in order to provide neurochemical characterization of medial hypothalamic neurons containing NK1-receptor mRNA. In order to identify NK1 receptors in cat brain, a 650-bp fragment of the cat NK1 cDNA was cloned. This fragment was used to synthesize a riboprobe for in situ hybridization. Partial DNA sequence analysis of the fragment indicated a 90% homology with human cDNA. In situ hybridization revealed the presence of NK1-receptor mRNA in cat hypothalamic neurons. Tissue used to localize NK1 receptors was also processed for glutamate immunopositivity. The results demonstrated that NK1-receptor mRNA is present in glutamate-immunopositive neurons in the anterior medial hypothalamus of cat, thus reinforcing the hypothesis that NK1 receptors play an important role in this neural circuit.

Aggressive Behavior, Increased Accumbal Dopamine, and Decreased Cortical Serotonin in Rats

Dopamine (DA) and serotonin have been implicated in the regulation of aggressive behavior, but it has remained challenging to assess the dynamic changes in these neurotransmitters while aggressive behavior is in progress. The objective of this study was to learn about ongoing monoamine activity in corticolimbic areas during aggressive confrontations in rats. Male Long-Evans rats were implanted with a microdialysis probe aimed at the nucleus accumbens (NAC) or medial prefrontal cortex (PFC); next, 10 min samples were collected before, during, and after a 10 min confrontation. Rats continued to display aggressive behavior while being sampled, and they performed two to six attack bites as well as 140 sec of aggressive acts and postures. Dopamine levels in NAC were significantly increased up to 60 min after the confrontation. Peak levels of 140% were achieved approximately 20-30 min after the confrontation. No concurrent changes in accumbal serotonin levels were seen during or after the confrontation. Dopamine and serotonin levels in PFC changed in the opposite direction, with a sustained decrease in serotonin to 80% of baseline levels during and after the confrontation and an increase in dopamine to 120% after the confrontation. The temporal pattern of monoamine changes, which followed rather than preceded the confrontation, points to a significant role of accumbal and cortical DA and 5-hydroxytryptamine in the consequences as opposed to the triggering of aggressive acts. The increase in accumbal DA in aggressive animals supports the hypothesis that this neural system is linked to the execution of biologically salient and demanding behavior.

Aminergic neuron systems of lobsters: morphology and electrophysiology of octopamine-containing neurosecretory cells.

In the American lobster (Homarus americanus) the biogenic amines serotonin and octopamine appear to play important and opposite roles in the regulation of aggressive behavior, in the establishment and/or maintenance of dominant and subordinate behavioral states and in the modulation of the associated postural stances and escape responses. The octopamine-containing neurosecretory neurons in the thoracic regions of the lobster ventral nerve cord fall into two morphological subgroups, the root octopamine cells, a classical neurohemal group with release regions along second thoracic roots, and the claw octopamine cells, a group that selectively innervates the claws. Cells of both subgroups have additional sets of endings within neuropil regions of ganglia of the ventral nerve cord. Octopamine neurosecretory neurons generally are silent, but when spontaneously active or when activated, they show large overshooting action potentials with prominent after-hyperpolarizations. Autoinhibition after high-frequency firing, which is also seen in other crustacean neurosecretory cells, is readily apparent in these cells. The cells show no spontaneous synaptic activity, but appear to be excited by a unitary source. Stimulation of lateral or medial giant axons, which excite serotonergic cells yielded no response in octopaminergic neurosecretory cells and no evidence for direct interactions between pairs of octopamine neurons, or between the octopaminergic and the serotonergic sets of neurosecretory neurons was found.

Effects of fenfluramine on ejaculatory function, luteinizing hormone and testosterone levels in men with hypogonadotropic hypogonadism and premature ejaculation.

Serotonergic neurotransmission is associated with the regulation of aggressive behaviour, anxiety and affect. Serotonin (5-HT) reuptake inhibitors (SRIs) have been extensively utilized in the treatment of affective disorders; however, their use often results in ejaculatory inhibition. Serotonin appears to modulate male sexual function through its influence on luteinizing hormone (LH) secretion but only when the steady state is altered. Premature ejaculation (PME) is defined as persistent or recurrent ejaculation with minimal sexual stimulation (DMS-III-R). While the aetiology of PME remains unclear, an underlying anxiety disorder may be a major contributing factor. It has been recently suggested that patients with premature ejaculation (PME) have an associated hypogonadotropic hypogonadism. This study was undertaken to determine whether the administration of the SRI fenfluramine would result in changes in PME (inhibitory effect) and release of LH which could be indirectly measured through an increase in the production of testosterone (disinhibitory effect). Six patients with PME and hypogonadotropic hypogonadism were treated with fenfluramine (20 mg). Both inhibition of PME (based on graded couple's responses) and increased plasma LH and testosterone levels occurred following treatment. These observations strongly suggest a role for serotonergic modulation in the occurrence of PME.

Nuclear receptor-mediated transcriptional control during organogenesis

The teleost fish nonapeptides, arginine vasotocin (AVT) and isotocin (IT), have been implicated in the regulation of social behavior. These peptides are expected to be involved in acute and transient changes in social context, in order to be efficient in modulating the expression of social behavior according to changes in the social environment. Here we tested the hypothesis that short-term social interactions are related to changes in the level of both nonapeptides across different brain regions. For this purpose we exposed male zebrafish to two types of social interactions: (1) real opponent interactions, from which a Winner and a Loser emerged; and (2) mirror-elicited interactions, that produced individuals that did not experience a change in social status despite expressing similar levels of aggressive behavior to those of participants in real-opponent fights. Non-interacting individuals were used as a reference group. Each social phenotype (i.e. Winners, Losers, Mirror-fighters) presented a specific brain profile of nonapeptides when compared to the reference group. Moreover, the comparison between the different social phenotypes allowed to address the specific aspects of the interaction (e.g. assessment of opponent aggressive behavior vs. self-assessment of expressed aggressive behavior) that are linked with neuropeptide responses. Overall, agonistic interactions seem to be more associated with the changes in brain AVT than IT, which highlights the preferential role of AVT in the regulation of aggressive behavior already described for other species.

Effects of Steroid Hormone Interaction on Activity and Home-Range Size of Male Lizards

Steroid hormones play a major role in influencing the physiology and behavior of all animals, including reptiles. Oftentimes, it is an interaction between two or more hormones that is ultimately responsible for the observed response or behavior. We designed a pair of field studies on adjacent communities of side-blotched lizards ( Uta stansburiana) to provide insight into the interrelationship of testosterone (T) and corticosterone (B) in regulating aggressive behavior. On one site, males were implanted with either T or saline (s), while on the other site males received either two S implants or both a T and a B implant (T + B). T increased both activity (by 31%) and home-range size (by 150%), whereas Simplanted cohorts exhibited a reduction in both of these parameters (by 24 and 50%, respectively). However, when B was given in combination with T, not only were the positive effects of T eliminated, but there was a reduction in activity (31%) and home-range size (72%) similar to that reported in lizards that received B implants alone. S-implanted cohorts in the T + B experiment increased their activity and home-range size by 15 and 43%, respectively. Although these latter changes in the S-implanted males are not statistically significant, they are indicative of a compensatory increase similar to that seen in the T and previously reported B outcrop experiments. Taken together, these results illustrate that regulation of aggressive behavior is complicated, with both hormonal and social interactions playing critical roles in determining an individual's home-range size and, hence, reproductive success.

GABA-mediated regulation of feline aggression elicited from midbrain periaqueductal gray

The midbrain periaqueductal gray (PAG) is now recognized as a critical structure for the initiation and regulation of aggressive behavior in the cat. The PAG is also known to be rich in γ-aminobutyric acid (GABA) receptors. In the present study, we sought to examine the possible role of this putative neurotransmitter in the modulation of affective defense and quiet biting attack behavior elicited by electrical stimulation of the PAG. Cannula-electrodes were employed for electrical stimulation as well as for microinjections of a GABA agonist (muscimol: 3, 12 and 22 pmol/0.25 μl) and GABA antagonist (bicuculline: 22 and 68 pmol/0.25 μl). After establishing predrug response threshold values for affective defense and quiet biting attack, these drugs were microinjected into the PAG sites from which these responses were elicited. Microinjections of muscimol (12 and 22 pmol) significantly suppressed the affective defense response in a dose- and time-dependent manner. Pretreatment with bicuculline (68 pmol) blocked the suppressive effects of muscimol (12 pmol) upon affective defense behavior. In contrast, this dose of muscimol failed to alter the response threshold for quiet biting attack behavior. Microinjections of vehicle alone (0.25 μl of saline,pH= 7.4) did not modify the thresholds for either of these responses. These results indicate that, at the level of the PAG, GABA-ergic mechanisms are selectively involved in the regulation of affective defense behavior in the cat.

The measurement of suicidality, aggressivity and impulsivity

Plutchik, Robert and van Praag, Herman: The Measurement of Suicidality, Agressivity and Impulsivity. Prog Neuro-Psychopharmacol & Biol Psychiat, 1989, 13 (Suppl): S23–S34) 1. 1. From an evolutionary point of view aggressive behavior increases the chances of individual survival as well as inclusive fitness. 2. 2. There are brain structures and biochemical systems that are involved in the regulation of aggressive behavior. 3. 3. Genetic studies have revealed genetic contributions to aggressive as well as impulsive behaviors. 4. 4. Research has demonstrated correlations betwen measures of suicidality, violence and impulsivity. 5. 5. A two-step model of countervailing forces has been developed that identifies amplifiers and attenuators of the aggressive impulse. This model has enabled us to determine a set of variables that influence suicide but not violence and another set that influences violence but not suicide.

Ultrasonic vocalizations and aggressive behavior in male rats

The aim of the present study was to know whether 22–28-kHz vocalizations have any communicatory role in the regulation of aggressive behavior in male rats of the Wistar strain. In pairs of intact rats 22–28-kHz vocalizations showed a positive correlation with the extent of aggressive behavior. The pattern of aggressive behavior during ultrasonic vocalizations was different from that just before and just after the vocalizations. However, surgically deafened rats were less active in aggressive behavior and more active in ambulatory activity in the open field than the controls. Muted rats were not different from the controls in both aggressive behavior and ambulatory activity. The present result that the deprivation of ultrasonic signals failed to increase aggressive behavior does not support the classical hypothesis that ultrasonic vocalizations inhibit the initiation of aggressive behavior. It is concluded that ultrasounds emitted during aggressive encounters may have little communicative value in male rats.

Role of the serotonin2-receptors in regulation of aggressive behavior.

1. Pirenperone, an antagonist of the serotonin2-receptors, in contrast to haloperidol, is a selective antagonist of apomorphine aggressiveness. Prolonged joint administration of definite doses of naloxone with apomorphine induces various subtypes of serotonin2-receptors, which is expressed in an inhibition of head shakings and the appearance of spontaneous aggressiveness after the administration of quipazine, a stimulator of serotonin2-receptors. 2. Cholecystokinin tetrapeptide significantly enhances the electrical pain aggressiveness and, in the same doses, decreases the number of head shakings induced by quipazine. Pirenperone is a selective blocker of the action of cholecystokinin tetrapeptide. 3. Cholecystokinin tetrapeptide may be an endogenous modulator of the sensitivity of the serotonin receptors. It is suggested that its functional role consists of activation of the serotonin2-receptors that turn on the defensive aggressive reactions.

The effects of apomorphine, d-amphetamine and chlorpromazine on the aggressiveness of isolated Aequidens pulcher (Teleostei, Cichlidae).

Apomorphine, d-amphetamine, chlorpromazine and dopamine, added to the aquarium water, were tested for their effects on the aggressive responses of isolated fish to mirrors and to models, compared with the responses of the same fish as non-treated controls tested at the start of, in the middle, and at the end of the experiment (Experiment 1). The effects of d-amphetamine administered by intracranial injection were also evaluated for responses to mirror presentations (Experiment 2). The three sets of controls in Experiment 1 indicate that the responses of the fish apparently changed over the 32-day experiment: they became more aggressive to mirrors whilst reacting less to models. Dopamine had no behavioural effect. Immersion in either apomorphine or d-amphetamine resulted in increased swimming activity, accompanied by apparent behavioural stereotypy. Immersion in apomorphine (Experiment 1) and intracranial injections of d-amphetamine (Experiment 2) also resulted in reduced aggression. Likewise, chlorpromazine also reduced some measures of overt aggression, whilst the appearance of other behaviours suggested that there is also an increased tendency to withdraw from the stimulus. It is concluded that the dopaminergic system plays an important role in the regulation of aggressive behaviour in this cichlid fish.

Memorisation des marques olfactives chez la Genette (Genetta genetta L.): durée de reconnaissance par les femelles de marques olfactives de males

Abstract and SummaryMemorization of Scent Marks in Genets (Genetta genetta L.): Duration of Female Memory of Male Scent Marks The aim of this work was to study the memorization of scent marks of known males by females in genets (Genetta genetta L.). An attempt was made to determine how long, after separation from a given male, females could discriminate between his scent marks and those of strange males. Significant differences in sniffing duration at the scent marks were observed nine weeks after separation. These results showed that olfactory cues could permit individual recognition in genets, and that memorizing the scent marks could also act in the regulation of aggressive behaviour in free‐living animals.

Effects of electrical stimulation of the medial aspect of the prefrontal cortex upon attack behavior in cats

An experiment was performed in order to determine the role of the medial aspect of the prefrontal cortex in the regulation of aggressive behavior in the cat. The results of this study demonstrated that electrical stimulation of the medial prefrontal cortex suppressed quiet biting attack, affective display elicited from electrical stimulation of the hypothalamus, and spontaneously elicited quiet biting attack. In contrast, stimulation of the prefrontal cortex did not measurably affect flight responses elicited from stimulation of the hypothalamus. The results of anatomical studies in the cat have suggested that inhibition of aggression is mediated indirectly upon the hypothalamus via the mediodorsal thalamic nucleus.

Neural Pathways from Thalamus Associated with Regulation of Aggressive Behavior

Small electrolytic lesions were made through electrodes in the thalamus of cats at sites where electrical stimulation elicited attack on a rat. Staining by modified Nauta reduced silver methods revealed that significant degeneration passed caudally from the lesions and entered the midbrain dorsal central gray region. Electrical stimulation of this dorsal midbrain region elicited attack on a rat, and destruction of this region suppressed the attack elicited by thalamic stimulation.

Ultrasonic studies in binary solutions of pyridine with water, methanol, and ethanol : Thomas, K.N., Stumpf, F.B., 53 (March 1973) 714–718

This experiment investigated the effects of rearing piglets in a multi-litter lactation system on piglet aggression at weaning. The following four pre-weaning treatments were applied to 72 sows and their litters (n = 642 piglets); (1) Farrowing crate (‘FC’ − n = 24 sows), (2) PigSAFE pens, in which sows and piglets are loose housed, (‘PS’ − n = 24 sows), (3) Farrowing crate and group lactation (‘GLFC’ − n = 12 sows), and (4) PigSAFE and group lactation (‘GLPS’ − n = 12 sows). FC and PS piglets remained in treatment from birth (day 0) until weaning (day 27). GLFC and GLPS piglets were housed in FC and PS, respectively, from day 0 to 14 after which they were transferred (with their dams) to group lactation pens (n = 6 sows and litters/pen), where they remained until weaning. Piglet weights were recorded at day 13 and 26. At weaning piglets were mixed into pens of four litters from FC, PS, or GL (2 GLFC litters and 2 GLPS litters) treatments and behaviour was continuously recorded for 2 h. Aggression (reciprocal and non-reciprocal aggression of duration <5 s) and fights (reciprocal aggression of duration ≥5 s; frequency; total and average duration, latency to fight) were recorded for each litter. Six piglets from each litter were randomly selected for skin lesion scoring on day 26 and 24 h post-weaning. GLFC and GLPS piglets had a lower growth rate than FC and PS piglets from day 13 to 26 (P < 0.01) but there was no difference in weight at day 13 (P = 0.11) or day 26 (P = 0.17), or in skin lesions at day 26 (P = 0.26). GL piglets delivered fewer bouts of aggression (P < 0.01), fought less frequently in the 2 h post-mixing at weaning (P < 0.01) and had sustained fewer skin lesions 24 h later (P < 0.01) than FC or PS piglets. GL piglets also had shorter fights (P < 0.01) and spent less total time fighting (P = 0.04) than FC, but not than PS, piglets. These results highlight the possible importance of the early social environment on the development and regulation of aggressive behaviour in the pig. Due to the implications of aggression and injury on both animal welfare and productivity, there is a need for further investigation into the effects of housing piglets in multi-litter lactation systems.

Efectos de la administración de LY354740, un agonista selectivo del grupo II de receptores metabotrópicos de glutamato, sobre la conducta agresiva en ratones

Estudios recientes han demostrado una implicación de los receptores metabotrópicos mGlu1 y mGlu5 en la regulación de la conducta agresiva. Este trabajo examina el efecto de la administración de LY354740 (4-16 mg/kg i.p.), un agonista selectivo de los receptores metabotrópicos del grupo II (mGlu2/3), en encuentros agonísticos entre ratones macho, utilizando un modelo de agresión inducida por aislamiento. 30 min tras de la administración del fármaco se llevaron a cabo interacciones agonísticas de 10 min de duración entre un animal aislado y un oponente anósmico en un área neutral. Dichos encuentros fueron grabados para su posterior análisis etológico, estimándose el tiempo pasado por los ratones en cada una de diez categorías conductuales. LY354740 (12 y 16 mg/kg) redujo significativamente las conductas ofensivas, sin afectar a la motilidad, en comparación con el grupo control. Estos resultados sugieren una implicación de los receptores mGlu del grupo II en la modulación de la agresión.