The effects of depo-medroxyprogesterone acetate (DMPA) on copulation-related and agonistic behaviors in an island colony of stumptail macaques (Macaca arctoides)

This study examined the effects on copulation-related and agonistic behaviors of repeated DMPA (depo-Provera) treatment of adult females in a heterosexual island colony of stumptail macaques (Macaca arctoides). Comparison of mean rates revealed a decrease in male approach to females and dominant male following of females after they were treated with DMPA. As treatment did not affect female genital present, female approach or follow of males, we conclude, consistent with earlier results, that DMPA primarily reduced female sexual attractiveness. DMPA treatment was also consistently associated with increased female agonistic behavior (i.e., low-level threat, bite, and fear grimace), with aggression directed primarily at subadults, juveniles, and infants. Treatment did not alter dominance relationships. These data suggest that DMPA treatment is associated with increased low-key contact aggression.

Haloperidol does not antagonize the effects of stress on aggressive behaviour in mice

The possibility that antipsychotic drugs antagonize the behavioural effects of stress on agonistic behaviour has been explored. Male mice of the OF.1 strain were subjected to the following treatments: 1) Immobilization stress (ten or twenty minutes in duration), 2) haloperidol (three doses) and 3) immobilization stress (ten minutes) plus haloperidol. Individually housed experimental animals confronted standard opponents (anosmic animals) in ten-minute encounters in a neutral cage. Encounters were videotaped and behaviour evaluated, assigning times allocated by subjects to eleven broad behavioural categories. The data show that stress markedly decreases attack behaviour, but haloperidol does not protect against the disruptive action of immobilization. On the contrary, stress and haloperidol produced additive effects further decreasing attack and increasing immobility.

Neonatal 6-hydroxydopamine alters the behavior of enriched-impoverished rats in a novel test environment

The hypothesis that neonatal norepinephrine (NE) depletion lessens the behavioral consequences of differential housing was tested. Male Wistar rats were injected with 6-hydroxydopamine (6-OHDA) or vehicle twice within 24 hr of birth, weaned at 25 days, and reared under either impoverished (IC) or enriched conditions (EC) for 30 days. In 3 experiments, rats were tested in the Morris water maze, the colony-intruder test, and 2 tests of dominance. 6-OHDA treatment reduced cortical and hypothalamic NE concentrations and increased brainstem NE concentrations. EC housing increased cortical dopamine (DA). Behavioral differences caused by postweaning enrichment-isolation were reduced by neonatal NE depletion, primarily in early test trials. The authors conclude that forebrain NE afferents from the locus coeruleus are important for housing-related behavioral changes and responsivity to novel testing environments.

Anabolic-androgenic steroids: Effects on social behavior and baseline heart rate

Examined the effects of anabolic-androgenic steroids (AS) on behavior, baseline heart rate (HR), and stress-induced HR responses. Twenty-four cynomolgus monkeys were assigned to four mixed social groups of both AS and sham control animals. For 2 months, AS-treated monkeys received biweekly injections of testosterone, and, on an identical schedule, the control animals were injected with a sham solution. Behavioral data revealed that AS disrupted the social milieu such that all dominant animals exhibited increases in dominant behavior and subordinates manifested increased submission. These changes returned to pretest levels 8 weeks following termination of the drug intervention. Affiliative behaviors decreased on the part of all animals as a function of AS and, with the exception of play behavior, failed to return to pretest levels after the 8-week period of recovery. AS created an increase in baseline HR, particularly among the dominant animals. Interestingly, the subordinate AS animals experienced a decrease in baseline HR response. AS had no apparent influence on stress-induced HR reactivity.

Behavioral, hormonal and neurochemical characteristics of aggressive alpha-mice

The present study examined the behavioral, neurochemical and endocrinological characteristics of aggressive, male alpha-mice. These mice inflict severe bite marks on other male mice in their cage, but are not attacked themselves. The characteristics of the alpha-mice were compared with those of submissive mice, and of control mice taken from cages in which no severe fighting was observed. The behavioral tests used were Porsolt's swim test of behavioral 'despair', a plusmaze test of anxiety, a holeboard test of exploration and locomotor activity, and a test of seizure threshold to bicuculline. The alpha-mice were found to be immobile in the swim test for a shorter time than the submissive and control mice, and the submissive mice for a longer time than the controls. In the holeboard, the alpha-mice spent less time making exploratory head-dips than the other mice. Submissive mice had elevated 5-HIAA levels in the hypothalamus, hippocampus and brainstem, and the alpha mice had reduced concentrations of dopamine in the brainstem. There were no significant differences in plasma corticosterone or testosterone concentrations between the groups. These findings indicate that in alpha-mice, a number of behavioral and neurochemical characteristics appear together with the unusually high aggressiveness towards cage-mates.

Behavioral and electroencephalographic effects of a depot type neuroleptic fluphenazine decanoate, in rats

The behavioral and electroencephalographic (EEG) effects of intramuscular fluphenazine decanoate (Fl-D) were investigated in rats and compared with those of fluphenazine enanthate (Fl-E) and fluphenazine HCl (Fl-HCl). It was clearly observed that 1) these two depot type neuroleptics reduced open-field activity, 2) antagonized methamphetamine-induced hyperactivity, 3) inhibited the conditioned avoidance response, and 4) produced catalepsy, for a substantially long period of time (4-35 d). Although both Fl-D and Fl-E significantly inhibited muricide in olfactory bulbectomized rats and impaired rotarod performance, these effects were relatively weak in potency and short-lasting (4 h-2 d). The EEG was changed to a drowsy pattern which consisted of high voltage slow waves following the injection of Fl-D and Fl-E. Fl-D significantly inhibited the EEG arousal response to auditory stimulation, but Fl-E did not. However, neither Fl-D nor Fl-E inhibited the EEG arousal response to electrical stimulation of the midbrain reticular formation and posterior hypothalamus. These results indicate that Fl-D has the same spectrum of pharmacological activity as Fl-E, except for its longer duration of action in antagonizing methamphetamine as well as in inhibiting the EEG arousal response to auditory stimulation.

[The development of pathological forms of behavior in submissive male C57BL/6J mice during agonistic zoosocial interactions. A possible model of depression?]

It is shown that a long experience of defeats in daily zoosocial collisions (ZC) elicits changes in the structure of submissive behaviour. Male mice of C57BL/6J line after 20 defeats demonstrated poses of passive subordination instead of active defence and run away which they manifested in the first ZC. Moreover, new immobile poses appeared which were rare in the first ZC. Submissive animals (CA) demonstrated a decrease of travels in the open field test and an increase of immobility time in the Porsolt test. Chronic administration of imipramine (10 mg/kg, i.p., twice a day during two weeks against the background of repeated ZC) prevented an increase of depressivity, estimated in Porsolt test. Changes were noted in the content of serotonin and 5-HIAA in some brain structures of subordinated mice in comparison to control animals (five days of isolation). The data are discussed from a position of the development of depression in SA of C57BL/6J line as a result of a long nonavoided zoosocial stress.

Diterpene sclareol glycol inhibits clonidine-induced aggressive responses in mice

The effects of a reversible activator of adenylate cyclase sclareol glycol (SG), a semisynthetic diterpene of the labdane family, on the aggressive behavior induced by a high dose of clonidine in mice were studied. SG was applied at doses well below the lethal dose. Aggressive behavior induced by clonidine at a dose of 30 mg/kg IP was decreased in a dose-dependent manner by SG (1, 5, 25 mg/kg IP). The aggressive responses were abolished by doses of 50 and 100 mg/kg. It is suggested that the inhibitory effects of SG on clonidine-induced aggressive behavior are realized mainly via its effect on adenylate cyclase and perhaps involving synaptic transmitter action.

Kainic acid lesions of the cat's midbrain periaqueductal grey region and emotional-defensive response evoked by carbachol injection to the same loci

Injections of carbachol (CCh) through a chronic cannula into the midbrain periaqueductal grey region (PAG) of the cat induced an emotional-defensive response (EDR) which was evaluated by duration and number of growls in a 30-min experimental session. That response was examined before and after injection of kainic acid (KA) to the same loci of midbrain. Injections of this excitotoxin into the PAG decreased EDR level. The degree of changes depended on the agent dose. A low KA dose (3 microgram/2 microliters) produced only prolongation of EDR latency, whereas a high dose of KA (6 micrograms/2 microliters) brought a statistically significant reduction of response level (reaching approximately 80%). The results have demonstrated the sensitivity of these cells of the PAG that are responsible for EDR.

[Behavioral correlates of aggressive motivation in male mice]

The behaviour was studied of male mice of CBA/Lac and C57BL/6j lines near transparent perforated partition in reaction to syngeneic partner which was in adjacent department of the common cage. The number of approaches to the partition and total time of staying near it during testing were used as behaviour parameters. Then the partition was removed and the success or defeat of each individual in agonistic collision and parameters of aggressive reaction of the winner male mouse were fixed. It turned out that future winners spent significantly more time near the partition than future losers. By the correlative analysis reliable interconnections were established between individuals activity near the partition (number of approaches or total time of staying) and intensity of aggression (number or total time of attacks) which reflects the level of the aggressive motivation. Variation is observed of individual correlating parameters depending on animals genotype and conditions of their keeping.

Alterations of serotonin neurotransmission and inhibition of mouse-killing behavior: III. Effects of minaprine, CM 30366 and SR 95191

Three closely related aminopyridazine derivatives: minaprine [3-(2-morpholino-ethylamino)-4-methyl-6-phenyl pyridazine, dihydrochloride], CM 30366 [3-(2-morpholino-ethylamino)-4-methyl-6-(4-hydroxyphenyl) pyridazine, hydrobromide] and SR 95191 [3-(2-morpholino-ethylamino)-4-cyano-6-phenyl pyridazine] were examined for their inhibitory effects on mouse-killing behavior (MKB). Three groups of killer rats were used: spontaneous killer rats (K rats) and nonkillers which became killers following para-chlorophenylalanine (PCPA) treatment or electrolytical destruction of the dorsal and median raphe nuclei. When given intraperitoneally (IP), the three drugs inhibited MKB of K rats without sedation. When given orally, minaprine showed no antimuricidal effect in K rats. After chronic IP administration of minaprine, MKB inhibition in K rats decreased after 25 days of treatment, probably because serotonin receptors became subsensitive. Minaprine and SR 95191, a derivative of minaprine, are inhibitors of type A monoamine oxidase (MAO), whereas CM 30366, a metabolite of minaprine, has no effect on MAO activity. SR 95191 displayed a similar MKB inhibition in the three groups of killer rats, and in this respect, it behaved like other type A MAO inhibitors. Minaprine and CM 30366 were less efficient in their antimuricidal effect in PCPA-treated and raphe-lesioned killer rats as compared with spontaneous killer rats. Moreover, the time courses of MKB inhibition and MAO A inhibition by minaprine did not correlate. The effects of minaprine on MKB seemed not related in a simple way to an alteration of serotonin level through MAO A inhibition, and rise the question of an alternative mechanism of antimuricidal action, until now unknown.

[Effects in animal models of depression of lisuride alone and upon coadministration with antidepressants]

Effects of lisuride, a central dopamine and serotonin agonist of the ergot type, in animal models of depression were investigated in comparison with those of desipramine, mianserin and rolipram. Lisuride, like desipramine and mianserin, inhibited reserpine-induced hypothermia in mice (0.5-5.0 mg/kg, i.p.) and suppressed muricide in olfactory bulbectomized rats (ED50 = 0.16 mg/kg, i.p.) in a dose-dependent manner. The anti-muricidal effect was slightly enhanced by the repeated administration of 0.25 mg/kg lisuride. Lisuride (0.05-0.25 mg/kg, i.p.), like desipramine, dose-dependently reduced the duration of immobility in rats forced to swim, and this effect was antagonized by haloperidol. The reduction of immobility time was enhanced by the repeated administration of lisuride; at the same time, the ambulation in rats increased. Furthermore, the immobility-reducing effects of desipramine and rolipram were markedly enhanced by the co-administration of a low dose of lisuride (0.025 mg/kg, i.p.), which by itself had no effect on the immobility time. These results indicate that lisuride may be useful for the treatment of depression and indicate that a low dose of lisuride may enhance the clinical effectiveness of antidepressants such as desipramine.

Dopamine autoreceptor agonists attenuate spontaneous motor activity but not spontaneous fighting in individually-housed mice

The present study was conducted to determine whether or not two behavioral characteristics of individually-housed mice, hyperactivity in a novel environment and intermale fighting, are attenuated by the dopamine (DA) agonists, apomorphine, (+)- and (-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine (3-PPP). Autoreceptor-activating doses of these drugs which reduced spontaneous activity in a novel environment did not inhibit spontaneous fighting with conspecific olfactory bulbectomized males. Individually-housed mice were more active in a novel environment and showed a significant reduction of activity at lower doses of apomorphine, (+)- and (-)-3-PPP than group-housed mice. However, the ED50's for the inhibition of spontaneous activity in a novel environment in group- and individually-housed mice were similar: apomorphine, 0.02 vs. 0.012 mg/kg, SC; (+)-3-PPP, 0.50 vs. 0.51 mg/kg, SC; and (-)-3-PPP, 1.0 vs. 0.56 mg/kg, SC, for group- and individually-housed mice respectively. A significant proportion of individually-housed mice, but not group-housed mice, displayed catalepsy in response to high doses of (-)-3-PPP. These data suggest that DA autoreceptor agonists can modulate the hyperactivity syndrome but not spontaneous fighting behavior in individually-housed mice.

Effects of the opiate antagonist naloxone upon hypothalamically elicited affective defense behavior in the cat

The opiate antagonist naloxone hydrochloride was employed in order to determine whether endogenous opioids play a role in the control of affective defense behavior elicited from the medial hypothalamus in the cat. The effects of naloxone upon quiet biting attack behavior elicited from the lateral hypothalamus were also assessed. A comparison of the differences in response latencies or thresholds before and after naloxone (i.p.) administration was made. Naloxone (1, 4 and 10 mg/kg) was found to significantly facilitate affective defense behavior in a dose- and time-dependent manner. The duration of facilitation ranged from 30 min after a 1 mg/kg injection to 180 min after a 10 mg/kg injection. The data also suggest that the effects of naloxone upon affective defense behavior are opposite to those seen with quiet biting attack. In two animals, quiet biting attack behavior was suppressed for 30 min following a 10 mg/kg injection of naloxone. Naloxone was also administered to cats in which hypothalamic stimulation elicited predatory responses coupled with components of affective defense behavior. In these cases, naloxone was ineffective in altering latencies for this 'mixed' response. These findings suggest that the opiate peptide system selectively inhibits affective defense behavior elicited from the medial hypothalamus of the cat.

Androgens, progestagens and agonistic behaviour: a review

The relationship between androgens, progestagens and agonistic behaviour is reviewed. Most literature concerned the effects of hormones on aggression; little information was available on hormonal influences on fear. Difference in aggression levels between males and females may be explained by assuming the existence of a gender difference in motivation, which, among other factors, is controlled by androgen and progestagen levels in peripheral blood. Androgens and progestagens are metabolised mainly by 5 alpha-reductase in the target organs. In the brain, aromatisation of testosterone also plays a role. The metabolites of testosterone may exert the same organising and activating influence as testosterone on juvenile and adult brain tissue, respectively. In some animal species testosterone secretion appears to be influenced by social and environmental variables. Conversely, alterations in plasma androgen levels have been found to affect behaviour. Dominant and/or aggressive individuals tend to show higher plasma testosterone levels than submissive and/or less aggressive animals. Among other mechanisms, competitive inhibition of androgen action at a central level, by progestagens acting as antagonists of androgens, may be important.

Alteration in hypnotic effect of pentobarbital following repeated agonistic confrontations in mice

We investigated how repeated agonistic confrontations affect the hypnotic effect of pentobarbital (PB) in male mice, using a resident-intruder paradigm. PB concentrations in the cortex, midbrain and brainstem were determined. Agonistic confrontations were terminated after 10 or 20 attack bites, and were repeated for 5 consecutive days. Immediately after the last encounter, PB (55 mg/kg, IP) was administered to both resident and intruder mice. Compared to the control group, intruders exposed to 20 daily attack bites showed a significant prolongation of the latency to sleep and a shortening of the duration of sleeping time. At the stage of induction, no significant difference in brain PB levels was found between the "defeated" and control intruders. At the stage of recovery, however, the "defeated" intruders showed a significantly low level of PB in all brain areas. In contrast, attacking resident mice did not show any significant changes in either the hypnotic effect or regional brain concentration of PB. Because pretreatment with naloxone prior to daily agonistic confrontation antagonized the alteration in PB-induced hypnosis, it seems that endogenous opioid mechanisms may participate in this phenomenon. The present study indicates that susceptibility to a hypnotic drug can be altered by chronic social conflict experience.

Temporal and sequential patterns of agonistic behavior: effects of alcohol, anxiolytics and psychomotor stimulants

Social and agonistic interactions are composed of a range of species-typical acts, postures, displays and other communicative signals that follow characteristic patterns. Descriptive and analytic methods permit an assessment of the temporal and sequential features of highly probable patterns of agonistic interactions. Analysis of the intervals that separate consecutive attacks by a resident mouse or rat toward an intruder identifies bursts or epochs of attacks. Amphetamine (1.25, 2.5 mg/kg), but not diazepam or alcohol, alters the burst pattern of attack behavior. Higher doses of alcohol, but not diazepam, in either resident male rats or in lactating rats confronting an intruder, reduce the sequences of aggressive acts and postures with high transition probabilities as identified by lag sequential analysis. These results suggest that temporal and sequential patterning mechanisms may be differentially altered by amphetamine- and alcohol-type substances. These neural for many types of behavior.

Facilitatory effects of caerulein on hypothalamic defensive attack in cats

Effects of intraventricularly microinjected caerulein (0.1, 1.0 and 10.0 micrograms) on the thresholds for hypothalamically elicited defensive attack and influences of haloperidol (0.5 mg/kg, i.p.) on the effects were studied in chronic cats. Directed attack and hissing were selected for threshold determination, and thresholds for these responses were measured under two situations: one with provocations by a human, and the other without such provocation. Results were as follows. (1) Caerulein lowered all thresholds in generally equal decrements and in a dose-related manner, accompanied by a general behavioral arousal. (2) Prior injection of haloperidol prevented the effects of caerulein, suggesting an antagonism-like interaction between haloperidol and caerulein. (3) Observed facilitatory effects of caerulein on the hypothalamic defensive attack were very similar to those observed with dopamine (DA) agonists such as methamphetamine and apomorphine and opposite to those with DA antagonists such as haloperidol and chlorpromazine. These findings suggest that caerulein exerts its facilitatory effects on the excitability of the ventromedial hypothalamic nucleus through its synergistic interaction with DA.

[Comparative characteristics of the parameters of an aggressive reaction in 2 mouse genotypes]

The parameters have been studied of the aggressive reaction of male mice of CBA/Lac and C57BL/6J lines differing by olfactory sensitivity to zoosocial pheromone stimuli. It has been shown that CBA males, characterized by a high olfactory sensitivity, have lower latency of the first attack than C57BL males with low olfactory sensitivity. A prolonged distant exposition to an unknown litter and male appearance lowers the latency of the first attack in mice of the studied lines proportionally to their meanings demonstrated after short time exposition. The number of attacks and total time of attacking is considerably higher in C57BL mice during the whole test period (15 min) than in CBA mice in which aggressivity is already sharply lowered after 5 min of agonistic interactions. The factors are discussed, influencing the parameters of mice aggressive reaction.

Effects of opiate agonists and antagonists on aggressive encounters and subsequent opioid-induced analgesia, activity and feeding responses in male mice

The effects of peripheral administration of the mu, kappa and sigma opiate agonists, levorphanol (1.0 mg/kg), U-50,488 (1.0 and 10.0 mg/kg), (+/-) SKF-10,047 (10.0 and 30.0 mg/kg), respectively, as well as the delta opiate antagonists, ICI-154,129 (10.0 mg/kg), and the prototypic antagonist, naloxone (1.0 mg/kg), on the agonistic behaviors and subsequent analgesic, locomotory and ingestive responses of subordinate mice were examined in a "resident-intruder" paradigm. The latter behaviors were examined in both defeated and nondefeated mice that had received an equivalent level of aggression. The mu and delta opiate antagonists decreased, while the mu, kappa, and sigma opiate agonists selectively increased aggressive behavior (number of bouts of aggressive interactions, number of bites to defeat, time to defeat). Both naloxone and the delta antagonist suppressed defeat- and aggression-induced activity and feeding, while only naloxone blocked the analgesic response. Levorphanol enhanced, U-50,488 had variable dose related effects, and SKF-10,047 decreased the defeat and aggressive-induced responses. These results indicate that various opioid systems and opiate receptors are differentially involved in the mediation of various components of the agonistic encounters and in the expression of the consequences of social conflict and defeat-induced opioid activation.