Behavioral effects of low, acute doses of d-amphetamine on the dyadic interaction between mother and infant vervet monkeys (Cercopithecus aethiops) during the first six postnatal months

A behavioral mechanistic investigation of the role of 5-HT1A receptors in the mediation of rat maternal behavior

Previous work suggests that 5-HT_1A receptors play a special role in rodent maternal aggression, but not in other aspects of maternal care (e.g. pup retrieval and nest building). The present study re-assessed the basic effects of 5-HT_1A activation or blockade on various maternal responses in postpartum female rats. We also examined the possible behavioral mechanisms underlying the maternal effects of 5-HT_1A. Sprague-Dawley mother rats were injected with a 5-HT_1A agonist 8-OH-DPAT (0.1, 0.5 or 1.0 mg/kg, sc), a 5-HT_1A antagonist WAY-101405 (0.1, 0.5 or 1.0 mg/kg, sc) or 0.9% saline solution on postpartum days 3, 5, and 7. Maternal behavior was tested 30 min before, 30 min, 120 min, and 240 min after the injection. Acute and repeated 8-OH-DPAT treatment significantly disrupted pup retrieval, pup licking, nursing, and nest building in a dose-dependent fashion, whereas WAY-101405 had no effect at the tested doses. The 5-HT_1A receptor specificity of 8-OH-DPAT's action was confirmed as its maternal disruption effect was reversed by pretreatment of WAY-100635 (a highly selective 5-HT_1A receptor antagonist). Subsequent pup preference test found that 8-OH-DPAT did not decrease the pup preference over a novel object, thus no inhibition on maternal motivation or maternal affect. The pup separation test and pup retrieval on an elevated plus maze test also failed to find any motivational and motor impairment effect with 8-OH-DPAT. However, 8-OH-DPAT at the maternal disruptive dose did disrupt the prepulse inhibition (a measure of attentional function) of acoustic startle response and enhanced the basal startle response. These findings suggest that stimulation of 5-HT_1A receptors by 8-OH-DPAT impairs maternal care by partially interfering with the attentional processing or basal anxiety. More work is needed to further delineate the psychological and neuronal mechanisms underlying the maternal disruptive effect of 5-HT_1A receptor activation.

Differential effects of acute amphetamine and phencyclidine treatment and withdrawal from repeated amphetamine or phencyclidine treatment on social interaction and social memory in rats

Although animal models based on amphetamine (AMPH) or phencyclidine (PCP) treatment have been used extensively to study the neurobiological and behavioral characteristics of schizophrenia, there are conflicting reports regarding their validity in modeling the negative symptoms and cognitive deficits of schizophrenia. The present study examined how acute AMPH or PCP treatment (Experiment 1) and withdrawal from repeated AMPH treatment (Experiment 2) or PCP treatment (Experiment 3) affects social behavior and social recognition memory in male Sprague-Dawley rats. Each subject was tested on two consecutive days. On the first day, the rats were tested four times (5 min/each) at 10-min intervals with the same partner rat (termed "AAAA" day). One day later, the rats were tested with the previous partner in the first three sessions and with a new partner rat in the final session (termed "AAAB" day). The results show that acute AMPH treatment (1.5 mg/kg, sc) significantly reduced the time spent on social interaction, but did not affect social recognition on the first day. Acute AMPH only disrupted social recognition on the second day of drug testing. In contrast, acute PCP treatment (2.0 mg/kg, sc) had no effect on time spent on social interaction, but did significantly disrupt social recognition on both days. Withdrawal from repeated AMPH (3.0 mg/kg/day for 7 days, ip) or PCP (5.0 mg/kg/twice daily for 7 days, ip) treatment did not affect social interaction or social recognition, indicating a lack of long-term detrimental effect of repeated AMPH or PCP treatment. These results suggest that acute AMPH treatment at a low dose (1.5 mg/kg) may be useful in modeling social withdrawal symptoms of schizophrenia, whereas acute PCP treatment at a similar dose range (2.0 mg/kg) may be useful in modeling the social cognitive deficit of schizophrenia.

The role of mesocorticolimbic dopamine in regulating interactions between drugs of abuse and social behavior

The use of addictive drugs can have profound short- and long-term consequences on social behaviors. Similarly, social experiences and the presence or absence of social attachments during early development and throughout life can greatly influence drug intake and the susceptibility to drug abuse. The following review details this reciprocal interaction, focusing on common drugs of abuse (e.g., psychostimulants, opiates, alcohol and nicotine) and social behaviors (e.g., maternal, sexual, play, aggressive and bonding behaviors). The neural mechanisms underlying this interaction are discussed, with a particular emphasis on the involvement of the mesocorticolimbic dopamine system.

Social withdrawal following amphetamine administration to marmosets

Approaches and leaves from social encounters by marmosets which had received amphetamine injected either intramuscularly or into the nucleus accumbens or caudate nucleus were recorded and used to determine whether social behaviour was disrupted as a result of behavioural competition or more active social withdrawal. The social isolation observed after the marmosets had received an IM injection of amphetamine (2 mg/kg) was not due to drug-induced increases in alternative behaviours. Drugged animals immediately withdrew from social encounters, interrupting their stereotypies in order to do so, whenever they were approached by an undrugged animal. In contrast, the reduced time spent in social encounters following amphetamine injections into the nucleus accumbens (10, 20 or 40 micrograms) appeared to be a direct consequence of the concurrent increase in locomotion. Animals continued to initiate social encounters despite being hyperactive. Amphetamine injections into the caudate nucleus were without effect on any of the social or individual behavioural measures.

Effects of d-amphetamine on grooming and proximity in stumptail macaques: differential effects on social bonds

An experiment was conducted to determine the effects of d-amphetamine on the expression of certain social behaviors, i.e., grooming and proximity, initiated by adult male stumptail macaques living in a large group comprised of both sexes and all ages. Traditionally, grooming behavior and proximity behavior have been considered indicators of social affinity. Under the non-drug conditions of the present study, the two types of behaviors were initiated in greatly different proportions toward individual members of the group. The acute administration of d-amphetamine (0.01-0.3 mg/kg IM) resulted in marked increases in the rate of self-grooming, i.e., the number of self-grooming bouts initiated per hour, for all subjects and in decreases in the rate at which subjects groomed other monkeys, but the drug appeared to have no effect on the rate at which a subject positioned itself near another monkey (proximity). Consequently, the drug had different effects on the two relationships represented by grooming behavior and proximity behavior. Drug administration also produced changes in the distribution of grooming and proximity initiated by the subjects toward various classes of interactants in the group. Furthermore, the changes were not of the same magnitude for the two behaviors. These data provide additional evidence that different group members receive differential behavioral interactions from drugged subjects.

Effect of d-amphetamine and diazepam on the greeting behavior of rhesus monkeys (Macaca mulatta)

The greeting behavior of rhesus monkeys (Macaca mulatta) was evaluated in a pharmacological test. It was observed in pairs of juvenile subjects reunited after a separation of two days. The observational measures were the duration of greeting behavior (social grooming, social play, and huddling) and the frequency of presentations, mounts and solicitations. d-Amphetamine (0.2 and 0.1 mg X kg-1) was found to shorten the duration of greeting behavior and increase the frequency of presentations and mounts. Diazepam (1 and 0.5 mg X kg-1) was found to prolong the duration of greeting behavior.

Stereotypy in monkeys and humans

Stereotyped movements are described in monkeys and humans and are classified as arising from constraint, sensory deprivation in infancy, amphetamine treatment or psychotic states. It is argued that, with the exception of cage stereotypies, stereotyped behaviour is evidence of abnormality in the nervous system consequent upon distorted maturational processes, organic defect or biochemical disturbance. Stereotypy is associated with a state of cognitive inflexibility and social and sensory isolation in humans and monkeys. It is suggested that, while no simple biochemical disturbance in the brain can describe these various occurrences of stereotypy, the cross-species occurrence of a syndrome of isolation, cognitive inflexibility and stereotypy implies a related mechanism mediating these divergent effects. If stereotypy is regarded as a consequence of failure to use sensory input to direct behaviour, therapeutic regimes designed to stimulate responsive behaviours and social interactions are more likely to be effective in the long run than direct attempts to suppress stereotypy.

Disruption of primate social behavior by d-amphetamine and cocaine: differential antagonism by antipsychotics

Psychostimulants lead to withdrawal from social interactions and to a decline of affective behavior in squirrel monkeys. These changes, in addition to motor stereotypies, may be related to stimulant-induced psychosis in humans. In the first of two series of experiments, 1 mg/kg d-amphetamine or 10 mg/kg cocaine, administered orally three times over 24 h to one adult male member of an established group (n = 6-9), engendered stereotyped movements of the head and hands, reduced rest postures, and greatly reduced all forms of social initiatives. Chlorpromazine (0.25-1.0 mg/kg), haloperidol (0.25, 0.5 mg/kg), and physostigmine (0.04, 0.08 mg/kg), administered before the third amphetamine or cocaine injection, blocked the motor stereotypies and hyperactivity. Chlorpromazine, haloperidol, and physostigmine did not reliably antagonize the pronounced reduction in social behavior. The second series of experiments focused on agonistic behavior in the context of resident-intruder confrontations and on affiliative behavior toward group members. d-Amphetamine (3 X 0.5 mg/kg) and, to a lesser extent, cocaine (3 X 10 mg/kg) decreased affiliative and agonistic behavior. Chlorpromazine (0.5, 1.0 mg/kg) and haloperidol (0.1, 0.25 mg/kg) did not block the severe disruption of the affiliative and agonistic behavior in amphetamine-treated monkeys; physostigmine (0.06 mg/kg) reversed the decline in time spent close to the familiar monkey in amphetamine-treated monkeys. By contrast, stimulant-induced stereotypies were effectively antagonized by chlorpromazine, haloperidol, and physostigmine. These results suggest that psychostimulant-induced changes in primate social behavior may be mediated by mechanisms other than those underlying motor stereotypies.

Analysis of amphetamine effects on agonistic and affiliative behavior in squirrel monkeys (Saimiri sciureus)

Two series of experiments were performed to differentiate the effects of d-amphetamine on social interactions from those on solitary motor behavior in adult and juvenile squirrel monkeys. In the first experiment, d-amphetamine (3x0.5 mg/kg, PO) induced pronounced stereotyped movements of the head, limbs and torso. When confronted in the colony room with an intruder monkey, the amphetamine-treated resident monkey showed reduced threat and attack behavior. In a separate test for affiliation, amphetamine nearly abolished the affiliative response toward a familiar group member. In a second series of experiments, d-amphetamine (0.3, 1.0 mg/kg, IM) decreased the affiliative behavior of juvenile monkeys towards their mothers; yet, in the presence of an unfamiliar adult male, the detrimental effect of amphetamine on affiliative behavior was prevented. Morphine (0.5, 2.0 mg/kg) increased the affiliative response toward the mother, and chlordiazepoxide (5, 10 mg/kg) was without effect in this situation. These observations suggest that amphetamine impairs a range of social behavior in adult and juvenile monkeys. The general disruption of agonistic and affiliative behaviors due to amphetamine appears to be based on mechanisms which differ from those mediating stereotyped movements. Stimulant-induced changes in social interactions in primates may be linked to disturbed affect.

Amphetamine and maternal behavior: dose response relationships

Primiparous rats received 0.05, 0.25, 0.50, or 1.50 mg d-amphetamine/kg body weight, injected IP, when offspring reached 3-4 and 10-11 days of age. A multidimensional analysis of their maternal behavior revealed that at doses as low as 0.25 mg/kg, amphetamine had a disruptive effect on mother-pup intercontact interval, retrieval latency, inter-retrieval interval, number of pup retrieved and number of corners to which they were retrieved, time nest building, number of paper strips used, nursing time, time in motion, and number of squares entered. Disruption was dose-dependent for all the preceding except number of corners and time nest building. Amphetamine had no effect on the rate of maternal locomotion. The impact of amphetamine on nursing was significantly greater at pup ages of 3-4 days than at 10-11 days. Drug-induced augmentation of arousal exceeding optimal levels for adequate care-giving and locomotor stimulation incompatible with elements of maternal behavior may account for dose-dependent impairment in the range of 0.25 to 1.50 mg/kg d-amphetamine.

Social isolation and other behavioral changes in groups of adult vervet monkeys (Cercopithecus aethiops) produced by low, nonchronic doses of d-amphetamine

Doses (0.1--0.7 mg/kg body weight) d-amphetamine were administered to three independent groups of green vervet monkeys (Cerecopithecus aethiops). Each group formed a triad with one male and two females. Amphetamine changed both the individual and the social behavior patterns significantly. Stereotypy and social isolation (withdrawal) were characteristic features of the amphetaminized animals. Also stereotyped social grooming was observed. The results are discussed in relation to behavior changes seen in amphetamine psychoses and in naturally occurring endogenous psychoses. It is emphasized that the study of patterns of behavior is an important object of research and relevant line in future investigations on psychopathology.