Effects of alpha and beta adrenergic antagonists on aggressive behavior in male mice

Norepinephrine function in personality disorder: plasma free MHPG correlates inversely with life history of aggression

OBJECTIVE

Clinical and pre-clinical data suggest the possibility of a facilitory role for norepinephrine (NE) in impulsive-aggressive behavior. While clinical studies have focused on putative central measures of NE activity, few studies have been published using peripheral measures. In this study, the relationship between plasma free NE metabolite, plasma free 3-methoxy-4-hydroxyphenylglycol (pMHPG), and impulsive aggression was explored in subjects with personality disorder.

METHODS

Subjects were 30 male subjects with personality disorder in whom basal plasma free MHPG concentrations were obtained. Aggression was assessed using the Life History of Aggression (LHA) assessment and the Buss-Durkee Aggression scales; impulsivity was assessed using the Barratt Impulsiveness and the Eysenck Personality Questionnaire Impulsivity scales.

RESULTS

A significant inverse correlation was found between LHA-Aggression and pMHPG in these subjects. Correlations with other behavioral measures were not statistically significant. pMHPG was significantly lower among subjects with borderline personality disorder but not significantly lower after controlling for LHA-Aggression scores.

CONCLUSION

These data suggest that pMHPG is inversely correlated with life history of aggression in subjects with personality disorder and that central and/or peripheral NE may play a role in modulating aggressive behavior in these subjects.

Catecholaminergic involvement in the control of aggression: hormones, the peripheral sympathetic, and central noradrenergic systems

Noradrenaline is involved in many different functions, which all are known to affect behaviour profoundly. In the present review we argue that noradrenaline affects aggression on three different levels: the hormonal level, the sympathetic autonomous nervous system, and the central nervous system (CNS), in different, but functionally synergistic ways. Part of these effects may arise in indirect ways that are by no means specific to aggressive behaviour, however, they are functionally relevant to it. Other effects may affect brain mechanisms specifically involved in aggression. Hormonal catecholamines (adrenaline and noradrenaline) appear to be involved in metabolic preparations for the prospective fight; the sympathetic system ensures appropriate cardiovascular reaction, while the CNS noradrenergic system prepares the animal for the prospective fight. Indirect CNS effects include: the shift of attention towards socially relevant stimuli; the enhancement of olfaction (a major source of information in rodents); the decrease in pain sensitivity; and the enhancement of memory (an aggressive encounter is very relevant for the future of the animal). Concerning more aggression-specific effects one may notice that a slight activation of the central noradrenergic system stimulates aggression, while a strong activation decreases fight readiness. This biphasic effect may allow the animal to engage or to avoid the conflict, depending on the strength of social challenge. A hypothesis is presented regarding the relevance of different adrenoceptors in controlling aggression. It appears that neurons bearing postsynaptic alpha2-adrenoceptors are responsible for the start and maintenance of aggression, while a situation-dependent fine-tuning is realised through neurons equipped with beta-adrenoceptors. The latter phenomenon may be dependent on a noradrenaline-induced corticosterone secretion. It appears that by activating very different mechanisms the systems working with adrenaline and/or noradrenaline prepare the animal in a very complex way to answer the demands imposed by, and to endure the effects caused by, fights. It is a challenge for future research to elucidate how precisely these mechanisms interact to contribute to functionally relevant and adaptive aggressive behaviour.

Influence of 5-HT1A receptor antagonism on plus-maze behaviour in mice. II. WAY 100635, SDZ 216-525 and NAN-190

To understand further the role of 5-hydroxytryptamine receptor subtype 1A (5-HT1A) mechanisms in anxiety, the behavioural effects of 5-HT1A receptor antagonists with different selectivity and intrinsic activity were examined using an ethological version of the murine elevated plus-maze test. WAY 100635 (0.03-9.0 mg/kg) produced a behavioural profile indicative of an anxiolyticlike effect, with an apparent bell-shaped dose-response relationship and increases in nonexploratory behaviours at the largest dose tested. SDZ 216-525 exerted a dose-dependent antianxiety action at doses of 0.05-0.8 mg/kg, with some loss of activity at 3.2 mg/kg. In contrast, smaller doses of NAN-190 had a significant effect, whereas higher doses (2.5-10.0 mg/kg) decreased locomotor activity and other active behaviours, a profile similar to that produced by the alpha1-adrenoceptor antagonist prazosin (2.5 mg/kg), which also inhibited open arm activity. Findings are discussed in relation to 5-HT1A receptor and alpha1-adrenoceptor antagonism and corresponding neurochemical changes. The results of the present series support the view that 5-HT1A receptor antagonists have therapeutic potential in the management of anxiety.