Ethopharmacology of Flight Behaviour. In: Olivier B, Mos J, Brain PF, editors. Ethopharmacology of Agonistic Behaviour in Animals and Humans. Dordrecht: Springer Netherlands; 1987. pp. 46-79. [DOI: 10.1007/978-94-009-3359-0_4]

An evolutionary approach to behavioral pharmacology: using drugs to understand proximate and ultimate mechanisms of different forms of aggression in mice

Psychoactive drugs (Fluprazine and Chlordiazepoxide--CDP) were used as probes to test both differences or similarities in neurochemical substrates (proximal causations) and adaptive significance (ultimate causations) of different forms of intraspecific aggression in wild mice and laboratory Swiss CD-1 counterparts. Fluprazine (1-5 mg/kg) inhibited maternal attack on female, but not on male intruders. Thus, phenotypically different attack behaviors (offence and defence respectively) which have different functions may be modulated by different neurochemical substrates. Intrasexual attack and infanticide which are phenotypically different, but share similar functions (i.e. competition for mates and resources) were equally inhibited by Fluprazine (2 mg/kg) both in males and females of wild and laboratory mice. This indicates that the neural substrates of these behaviors are related and similarly regulated in the two sexes. Fluprazine was used to test the prediction of the evolutionary model on fighting strategies in male-male asymmetric contests as far as fighting ability and resource value (mating and cohabitation with a female) are concerned. Fluprazine inhibited the intensity of fighting (i.e. more 'defensive' behavioral phenotype of attack) only in animals without previous positive fighting experience, suggesting that different behavioral strategies are based on different neurochemical modulation. Experience of attack also influenced the effects of CDP (2.5-5 mg/kg) in both lactating females and male resident mice. The reported proaggressive effects of benzodiazepines were observed only in animals with prior fighting experience in both cases. Thus the understanding of the effects of drugs on behavior demands consideration of the biological variability (e.g. genetic, previous experience and/or interindividual differences) and the adaptive significance of behavior in the experimental context. On this background ethopharmacology can be defined as an evolutionary approach to the study of a drugs effect on neurochemical mechanisms and functions of behavior.

Animal models and ethological strategies for early drug-testing in humans

The preclinical evaluation of psychotropic drugs relies on the use of animal tests which are thought to generate clinically relevant information concerning the psychiatric condition for which the drug can be used. Despite their importance, views on the usefulness of animal "models" vary widely, ranging from outright negation on the grounds that human minds are unique, to the more biological view that because of a partially common phylogenetic history, animals share many behavioural features with humans, e.g. learning, attention, aggression or sociality, which are altered in psychiatric disorders. The widespread use of ethology with its emphasis upon the function and origin of behaviour, particularly social behaviour, is based upon this evolutionary view. Many ethopharmacological tests in animals use situations which bias the animal's behaviour towards flight or sociality but their validation requires clinical feedback from humans. Unfortunately, information relating to human social mechanisms is rarely obtainable from conventional clinical-assessment schemes. To help overcome this problem, we have applied ethological principles to a new Challenge Interview Situation which is designed to bias the behaviour of healthy subjects towards flight. Analysis shows that by staring, moving closer or asking the subjects to relate emotional experiences, shifts in non-verbal behaviour towards avoidance and mild social withdrawal are achieved which resemble behavioural strategies recorded ethologically in depressed patients as well as animals in an arrested flight situation. The Challenge Interview is intended for early drug studies in humans where sociality is a target and can be adapted for concomitant endocrine and biochemical studies if required.

D-cycloserine enhances social behaviour in individually-housed mice in the resident-intruder test

D-Cycloserine (DCS) has been reported to affect the central nervous system in man. To investigate whether the compound produces specific behavioural effects, DCS was administered to male mice in a resident-intruder situation and the behaviour of the interacting mice assessed using ethological analysis. Resident mice given DCS (32.0-320.0 mg/kg PO, 60 min before testing) showed dose-dependent increases in social investigation, smaller increases in sexual behaviour and decreased aggressiveness. Defensive and flight behaviour were not affected. Intruder mice showed slight increases in sexual behaviour that were not dose-dependent, and small increases in social investigation. The increases in social investigation induced by DCS (320.0 mg/kg) in resident mice were not reversible with R-HA 966 (32.0 mg/kg IP, 30 min before testing), a blocker of the strychnine-insensitive glycine modulatory site associated with the N-methyl-D-aspartate receptor, but were blocked by the GABA antagonist bicuculline (0.56 mg/kg IP, 5 min before testing). The small DCS-induced increase in sexual behaviour in residents was reversed by R-HA 966. Within the parameters of the resident-intruder situation, DCS exerts socio-sexual behaviour-enhancing effects which are dependent upon the role of the interactant, and which are mediated by an action upon multiple substrates. DCS may be regarded as another example of a sociotropic (approach-promoting) agent.

Opposite effects of pentylenetetrazol on self-defensive and submissive postures in the rat

In a previous work, using the resident-intruder situation, we have shown that a benzodiazepine inverse agonist could exert a "fear-promoting" effect, in decreasing self-defensive behaviours while increasing submissive postures. To further test this hypothesis, the effects of pentylenetetrazol on different forms of defensive behaviour were examined in male intruder rats confronted with offensive residents. Administration of pentylenetetrazol (10 and 20 mg/kg, IP) increased submissive postures such as immobility and on-the-back, but reduced self-defensive postures. Other active behaviours were not reduced, thus excluding a non-specific behavioural suppression. These results suggest that self-defensive and submissive behaviours can be dissociated and that anxiogenic compounds are more likely to increase submissive behaviours than self-defensive ones.

Beta--CCE and FG 7142 increase defensiveness during intraspecies encounters in mice

The effects were ascertained of two partial inverse agonists at benzodiazepine receptors (beta-CCE and FG 7142) on the incidence of timid (defensive-escape), aggressive, sociable and locomotor activities in both timid and aggressive singly-housed male mice, treated with drugs in paired interactions with untreated non-aggressive males. FG 7142 (5 mg/kg) and beta-CCE (8 mg/kg) increased defenses and escapes without producing other behavioral changes in timid mice. FG 7142 (20 mg/kg) and beta-CCE (1-8 mg/kg) moderately increased defenses and alert postures in aggressive mice and this effect was associated with marked reduction of aggressive behavior. FG 7142 (20 and 80 mg/kg) also decreased walking across cage in aggressive mice. It is concluded that beta-CCE and FG 7142 produced behavioral changes which could be interpreted as "anxiogenic".

Opposite effects of agonist and inverse agonist ligands of benzodiazepine receptor on self-defensive and submissive postures in the rat

The effects of benzodiazepine receptor ligands on different types of defensive behaviours were examined in intruder male rats confronted with offensive residents. Chronic administration, via a subcutaneous silastic pellet, of a full agonist (diazepam) for 15 days increased self-defensive postures as well as social and non-social behaviour whereas submissive postures and flight were reduced. Acute administration of a partial agonist (ZK 91296) resulted in a similar increase in self-defensive postures and a decrease of submission and non-social elements. Acute administration of a partial inverse agonist (FG 7142) reduced defensive postures and social behaviour whereas submissive postures were increased. These results show that activation of benzodiazepine receptors by full or partial agonists increased self-defensive responses to attacks by a conspecific, while decreasing submissive postures. On the contrary, "inverse activation" of these receptors by an inverse agonist increased submissive postures while decreasing self-defensive responses. These data suggest that benzodiazepine receptors are involved in the control of the animal's strategy to respond to an attack of another rat.

Differential effects of six structurally related benzodiazepines on some ethological measures of timidity, aggression and locomotion in mice

The effects were compared of three 2' chlorophenyl-benzodiazepines (triazolam, clonazepam and lorazepam) and three corresponding 2' deschloro-phenyl-derivatives (alprazolam, nitrazepam and oxazepam, respectively) on the incidence of six ethological elements in both timid and aggressive singly-housed male mice, treated with drugs in paired interactions with untreated non-aggressive males. Alprazolam and oxazepam reduced defensive upright postures and escapes at doses which did not reduce rearing and actually increased walking, while their chlorinated counterparts (triazolam and lorazepam, respectively) decreased incidence of defenses and escapes mostly at doses decreasing locomotor acts involving a similar movement (rears and walks, respectively). Alprazolam and oxazepam also reduced attacks at doses not reducing rears, in contrast to triazolam and lorazepam which reduced attacks only at doses suppressing rearing. Nitrazepam stimulated sniffing partners much more than its chlorinated counterpart clonazepam. The 2' deschloro-phenyl-benzodiazepines were more potent in reducing defensive-escape activities than attacks or locomotion. Yet, none of the benzodiazepines tested produced a complete inhibition of timid defensive-escape behavior at non-sedative doses. The present study suggests that 2' deschloro-phenyl-benzodiazepines are less "sedative" with respect to their "anxiolytic" activity.

Serotonergic modulation of social interactions in isolated male mice

Several serotonergic drugs were tested in isolation-induced aggressive behavior in male mice using ethological methodology. Eltoprazine, a mixed 5-HT1 agonist, reduced aggression but enhanced social interest and exploration. Several 5-HT1A agonists (8-OH-DPAT, ipsapirone, buspirone, 5-Me-ODMT) and a 5-HT uptake blocker (fluvoxamine) also reduced aggression. Although these drugs somewhat differentially affect aggressive behavior, the isolation-induced paradigm alone is not sensitive enough to successfully differentiate and screen the various serotonergic drugs with regard to their influence on social behavior in mice. It is argued that various animal paradigms in several species are necessary to describe specific effects of serotonergic drugs.