Behavioral and endocrine aspects of dominance and submission in male rabbits

Small all-male groups of rabbits were studied for periods of 15–20 days in a seminatural setting, giving the animals the possibility of initiating and pacing their social interactions. Behavioral observations included: intermale activity recorded daily and the reactions to the occasional introduction of an intruder female. Hormones were measured in blood samples taken at the beginning and at the end of the experimental period. A combination of behavioral and endocrine parameters, rather than single measures, was used to assign each individual its social rank within each group. Tables of concordance between behavioral and endocrine parameters were compiled to evaluate the dominance and the subordination hierarchy. Different behavioral categories and elements characterized dominance and subordination, indicating the two as district rather than simply reciprocal traits. Their endocrine basis is also different, final levels of testosterone and estradiol being associated with dominance, and corticosterone, ACTH, and androstenedione with subordination. The same hormones in the initial samples were unrelated to the subsequent social status, indicating that hormones are not prerequisites of status. The relevance of specific behavioral and endocrine parameters is discussed.     

Some consequences of aggressive behavior: A selective review of the literature on other animals

Animal experiments in which the opportunity to aggress was positively reinforcing are surveyed, with attention paid to field and laboratory reports on play and play fighting. A distinction is drawn between ways in which aggressive behavior may be elicited and factors which increase or decrease the probability that aggression will be emitted. Since aggression may be emitted and may also be reinforcing, the possibility that aggressive behavior may be self-reinforcing is mentioned. In addition to positive reinforcement, consequences of aggressive behavior are presented. These include punishment, removal of a noxious stimulus, feeding, arousal, and disinhibition.     

Relationships between testosterone metabolism in the brain,other endocrine variables and intermale aggression in mice

Relationships between some endocrine variables (plasma testosterone and estradiol; in vitro gonadal biosynthesis from pregnenolone precursor and adrenocortical biosynthesis from progesterone precursor; in vitro activity of 17β-hydroxysteroid de-hydrogenase (17β-HSDH) and of aromatizing enzymes in the subcellular fractions of the brain) and isolation-induced inter-male aggressiveness were studied. A significant positive correlation was found between fighting behavior, measured by the number of wins in a series of paired encounters, and the activity of brain 17β-HSDH. A significant inverse correlation was found between fighting behavior and the activity of aromatizing enzymes in the nuclear fraction of the brain. No significant correlations were found between fighting and the other endocrine variables investigated. These results may suggest that the conversions testosterone → androstenedione and testosterone → estradiol in the brain play a role in the control of inter-male fighting in the mouse. These results may also account for the effect of repeated wins and defeats on brain steroidogenesis.     

Accelerated muscle contractility and decreased muscle steadiness following sauna recovery do not induce greater neuromuscular fatigability during sustained submaximal contractions

Acute whole-body hyperthermia (WBH) increases blood markers concentration of stress, impairs motor drive to exercising muscles, and decreases resistance to neuromuscular fatigability. The functional natural residual consequences of WBH on neuromuscular functions remain unclear. We aimed to investigate the effects of residual WBH on voluntary and electrically induced ankle plantar flexor contractility properties, motor drive transmission (reflexes), muscle torque steadiness, resistance to neuromuscular fatigability, and markers of stress as the body temperature recovers naturally to normothermia. WBH was induced by Finnish sauna bathing in 16 apparently healthy young (24 ± 4 years) adult men. Motor performance was monitored before and 2 h after the sauna, and immediately after submaximal exercise (120 s at 50% of maximal voluntary contraction). Markers of stress were monitored before and 2 h after the sauna. Finnish sauna exposure induced moderate to severe WBH (rectal temperature, 38.5–39.6 °C). At 2 h after the sauna, rectal temperature had recovered to the preheating level (preheating 37.11 ± 0.33 °C versus postheating 37.00 ± 0.29 °C, p > .05). Post-sauna recovery was accompanied by slowed salivary free cortisol diurnal kinetics, whereas noradrenaline, dopamine, and serotonin did not persist into the 2 h recovery after the sauna. Although recovery to normothermia after a sauna led to a greater acceleration of muscle contractility properties and decreased muscle steadiness, sustained isometric submaximal contraction did not provoke greater neuromuscular fatigability.     

Prenatal sex hormones and human aggression: A review,and new data on progestogen effects

We review data on aggression from psychological studies of offspring from two categories of abnormal prenatal sex hormone conditions: 1) endocrine disorders, and 2) hormone treatment during pregnancy. Both sources yield trends and some significant findings that are in line with the animal research based expectations of a positive androgen effect on the development of aggressive behavior. However, the available studies have many methodological weaknesses, and the results are not strong and open to interpretations by factors other than prenatal hormones. Potential modes of prenatal sex hormone effects are also discussed. In the second part, we present data on 13 boys and 15 girls who had been exposed to medroxyprogesterone acetate (MPA) in utero and on 28 closely pair-matched controls. The double-blind follow-up examination at age 9 to 14 years included questionnaires, half-structured interviews with mother and child separately, and a battery of psychological tests. Interviews were tape-recorded and rated by two independent raters. The results show weak but consistent differences, with the MPA-exposed subjects being lower in self- or mother-reported aggression than the controls. The results cannot be accounted for by differences in aggression-related rearing styles. However, the influence of pregnancy pathology cannot be totally excluded. We conclude that the available data are compatible with the hypothesis that prenatal sex hormones influence the development of human aggressive behavior. More sophisticated research studies are needed, however, to demonstrate hormonal effects and their mechanism of action in a reliable and valid fashion.     

Olfactory stimuli and intermale aggression in androgen-treated castrated sheep

The ability of olfactory stimuli to elicit aggression in male sheep was assessed in testosterone-treated castrates. Ablation of the olfactory bulbs (Exp. 1) did not reduce the capacity of sheep to participate in aggressive behaviour after testosterone treatment. Topical application of urine from castrates treated with propionated testosterone, 5α-dihydrotestosterone, 17β-oestradiol, or an oil vehicle to the fleeces of untreated castrates (Exp. 2) did not result in different levels of aggressive responsiveness in testosterone-treated castrates.     

The nature of sexual reinforcement.

Sexual reinforcers are not part of a regulatory system involved in the maintenance of critical metabolic processes, they differ for males and females, they differ as a function of species and mating system, and they show ontogenetic and seasonal changes related to endocrine conditions. Exposure to a member of the opposite sex without copulation can be sufficient for sexual reinforcement. However, copulatory access is a stronger reinforcer, and copulatory opportunity can serve to enhance the reinforcing efficacy of stimulus features of a sexual partner. Conversely, under certain conditions, noncopulatory exposure serves to decrease reinforcer efficacy. Many common learning phenomena such as acquisition, extinction, discrimination learning, second-order conditioning, and latent inhibition have been demonstrated in sexual conditioning. These observations extend the generality of findings obtained with more conventional reinforcers, but the mechanisms of these effects and their gender and species specificity remain to be explored.     

A multicomponent investigation of the interaction of generalized anxiety and phobia

Forty female undergraduates forming four groups, high or low trait anxiety with or without a specific fear (rats), participated in a psychophysiological assessment of their response to the phobic object, a neutral object (rabbit), and to a general anxiety-induction procedure (threat of shock). Subjects also completed a number of tasks requiring sustained attention. Blood samples were drawn to determine thyroid hormone (T3 and T4) levels. Trait anxiety was found to interact with specific fear in response to the feared object. The high-trait anxious/high-fear group was most physiologically responsive to the rat. Trait- anxious subjects were more responsive to the threat of shock and showed performance deficits on reaction time, vigilance, and backward digit span tasks. These subjects also had significantly higher T3 and T4 levels. The findings are discussed with regard to the role of general anxiety in the etiology and/or maintenance of specific fears and the role of thyroid hormones in accentuating physiological response to feared stimuli.     

Maternal Care and Individual Differences in Defensive Responses

Abstract— Familial transmission of mental illness is common. Recent studies in behavioral neuroscience and biological psychiatry reveal the importance of epigenetic mechanisms of transmission that center on the developmental consequences of variations in parental care. Studies with rats suggest that environmental adversity results in patterns of parent–offspring interactions that increase stress reactivity through sustained effects on gene expression in brain regions known to regulate behavioral, endocrine, and autonomic responses to stress. While such effects might be adaptive, the associated cost involves an increased risk for stress-related illness.     

Investigating the outcome of the initial assessment at a national transgender health service: Time to review the process?

Background: Globally, there is a lack of a standardized assessment process prior to the initiation of gender affirming medical interventions and consequently there is a discrepancy in this process among different transgender health services.

Aim: The main objective of this study is to investigate the outcome of the initial assessment process at a national transgender health service.

Method: The outcome of people over the age of 17 years, assessed at a large national transgender health service in the United Kingdom during a 2-year period was categorized into: (1) recommendation for cross-sex hormone treatment, or (2) no recommendation for cross-sex hormone treatment. In addition, 200 case notes were reviewed in order to investigate the level of agreement between the two clinicians involved in the assessment process.

Results: During the study period, a total number of 617 people completed their assessment at the service. Following assessment 380 (61.6%) patients were recommended for cross-sex hormone treatment, leaving 237 (38.4%) patients who required a longer assessment period or were discharged. The factors associated with being recommended for cross-sex hormone treatment were having socially transitioned, not smoking, having initiated cross-sex hormones prior to assessment, being older, and assigned male at birth. Out of the 200 case notes reviewed, agreement between assessor 1 and 2 (3 months apart) was found in 88% (n = 176) of the cases.

Discussion: Although the results of the study may not be generalizable to other international centers, questioning the assessment process and the role of the assessors is important to ensure treatment is offered in a timely and efficient manner. The findings from this study suggest that the routine inclusion of two assessors needs to be reviewed.