Understanding and Preventing Violence, Volume 2: Biobehavioral Influences (1994)
Chapter: INFRAHUMAN PRIMATE STUDIES
Because of the need to examine the effects of antihormones on ethologically assessed behavior, several reinvestigations have recently been conducted with rats and mice, in which the resultant behavior in a variety of pairings has been analyzed in detail using videotaped records. These studies on the antiandrogen cyproterone acetate, antiestrogens (tamoxifen and CI 680), and progesterone are listed in Table 6. The basic conclusions are that cyproterone acetate suppresses "hostility" in rodents only by reducing the production of androgen-dependent "pheromones" (odor cues). Tamoxifen and CI 680, on the other hand, seem to have real potential as antihostility agents in some forms of attack as assessed in laboratory rodents. Progesterone (and progesterone derivatives such as MPA) produce antiandrogenic effects, blocking the production of gonadal and adrenal androgens in male animals. They also possibly exert calming effects via an anesthetic action (P'an and Laubach, 1964), a property that has been said to account for the hormone's induction of lordosis in rats (Meyerson, 1967).
It is interesting to note that Poshivalov (1982) reported that acute injections of LHRF enhanced intermale social aggression in laboratory mice. Lincoln (1987) similarly found that the LHRF agonist buserelin increased both testosterone levels and aggressive behavior in male red deer (Cervus elaphus).
One should comment that the consequences of winning or losing encounters on the HPA and HPG axes, as well as on the secretion of medullary hormones in male lower vertebrates, generate patterns of changes that seem likely to intensify dominance-subordination polarities and/or facilitate social group living. The "winner" tends to show relatively augmented testosterone (increasing male dominance and masculine cues), relatively reduced adrenocortical activity (facilitating body weight increases and gonadal function), and increased norepinephrine (again related to increased active aggressiveness). The "loser" shows the opposite responses and generally becomes more passive, ''learns" submissive responses, and elicits less attack.
INFRAHUMAN PRIMATE STUDIES
Dixson (1980) reviewed the data suggesting that intermale aggression increases during the mating season in a number of primate species including Lemur catta, Saimiri sciureus, and Macaca mulatta. It is established that testosterone levels increase at this time. Dixson stressed that these correlations do not demonstrate a causal relationship between changes in testosterone and aggressive
TABLE 6 Recent Ethoexperimental Studies with Antihormones in Rodents
|
Authors |
Material Studied |
Male Subjects |
Impact on Subject's Sex Accessory Weights |
Impact on Behavior |
|
Simon et al. (1987) |
Cyproterone acetate |
Paired individually housed mice |
Suppresses weights |
Reductions in offense only when both animals received drug. The antiandrogen augments threat and attack in encounters with non-drug-treated opponents and influences sexual activity, social investigation, and immobility. |
|
Brain et al. (1988) |
Tamoxifen |
Lister hooded rats |
No great influence |
Markedly reduces time allocated to offense. |
|
Hasan et al. (1988) |
Tamoxifen |
TO strain mice |
No great influence |
Dose dependent effects—but generally reduces offense—changing investigatory behavior at lower doses. |
|
Brain et al. (1988) |
CI 680 |
OFI strain mice |
No great influence |
Reduces time allocated to offense. |
|
Brain and Hasan (1989) |
Progesterone |
Lister hooded rats |
Suppresses weights |
Progesterone reduces offense but also produces pronounced immobility and suppresses sexual behavior. |
