Increased paternal corticosterone exposure influences offspring behaviour and expression of urinary pheromones.

BACKGROUND: Studies have shown that paternal stress prior to conception can influence the innate behaviours of their offspring. The evolutionary impacts of such intergenerational effects are therefore of considerable interest. Our group previously showed in a model of daily stress that glucocorticoid treatment of adult male mouse breeders prior to conception leads to increased anxiety-related behaviours in male offspring. Here, we aimed to understand the transgenerational effects of paternal stress exposure on the social behaviour of progeny and its potential influence on reproductive success. RESULTS: We assessed social parameters including social reward, male attractiveness and social dominance, in the offspring (F1) and grand-offspring (F2). We report that paternal corticosterone treatment was associated with increased display of subordination towards other male mice. Those mice were unexpectedly more attractive to female mice while expressing reduced levels of the key rodent pheromone Darcin, contrary to its conventional role in driving female attraction. We investigated the epigenetic regulation of major urinary protein (Mup) expression by performing the first Oxford Nanopore direct methylation of sperm DNA in a mouse model of stress, but found no differences in Mup genes that could be attributed to corticosterone-treatment. Furthermore, no overt differences of the prefrontal cortex transcriptome were found in F1 offspring, implying that peripheral mechanisms are likely contributing to the phenotypic differences. Interestingly, no phenotypic differences were observed in the F2 grand-offspring. CONCLUSIONS: Overall, our findings highlight the potential of moderate paternal stress to affect intergenerational (mal)adaptive responses, informing future studies of adaptiveness in rodents, humans and other species.

Paternal early life stress exerts intergenerational effects on male C57Bl/6J offspring risk-taking behaviors and predator scent-induced c-Fos expression.

Paternal preconceptional health factors, such as exposures to stress, diet and exercise, have been found to significantly influence offspring phenotypes in a range of animal models. Preclinical studies have provided evidence that paternal stress is associated with increased stress responsivity and anxiety-related traits, particularly in male offspring. It was previously reported that a paternal history of maternal separation (MS) led to male offspring (PatMS) displaying reduced cautious behavior during exploration of a novel environment. The neural basis for that absence of behavioral moderation is unclear. Here, we investigated the adaptive behavioral responses of control and PatMS male offspring in the predator odor risk-assessment task (PORT). PatMS mice failed to moderate their behaviors in the presence of a predator odor 2,4,5-trimethylthiazoline (TMT). c-Fos mapping revealed reduced cellular activation in fear-regulating brain regions of PatMS mice, such as in the cingulate cortex, dentate gyrus of the hippocampus and the basolateral amygdala. Expression of the paternally imprinted gene Grb10 (previously identified as a key molecular regulator of risk-taking behavior) was unaltered in PatMS mice. However, other paternal imprinted genes such as Igf2 and PEG3 were differentially expressed in PatMS mice. Overall, our study provides the first evidence of an intergenerational influence of preconceptional paternal stress exposure on offspring brain zunction relevant to risk-taking behavior, which is also independent of Grb10 gene expression.

A Preclinical Model of Computerized Cognitive Training: Touchscreen Cognitive Testing Enhances Cognition and Hippocampal Cellular Plasticity in Wildtype and Alzheimer's Disease Mice.

With the growing popularity of touchscreen cognitive testing in rodents, it is imperative to understand the fundamental effects exposure to this paradigm can have on the animals involved. In this study, we set out to assess hippocampal-dependant learning in the APP/PS1 mouse model of Alzheimer's disease (AD) on two highly translatable touchscreen tasks - the Paired Associate Learning (PAL) task and the Trial Unique Non-Matching to Location (TUNL) task. Both of these tests are based on human tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and are sensitive to deficits in both mild cognitive impairment (MCI) and AD. Mice were assessed for deficits in PAL at 9-12 months of age, then on TUNL at 8-11 and 13-16 months. No cognitive deficits were evident in APP/PS1 mice at any age, contrary to previous reports using maze-based learning and memory tasks. We hypothesized that daily and long-term touchscreen training may have inadvertently acted as a cognitive enhancer. When touchscreen-tested mice were assessed on the Morris water maze, they showed improved task acquisition compared to naïve APP/PS1 mice and wild-type (WT) littermate controls. In addition, we show that touchscreen-trained WT and APP/PS1 mice show increased cell proliferation and immature neuron numbers in the dentate gyrus compared to behaviorally naïve WT and APP/PS1 mice. This result indicates that the touchscreen testing paradigm could improve cognitive performance, and/or mask an impairment, in experimental mouse models. This touchscreen-induced cognitive enhancement may involve increased neurogenesis, and possibly other forms of cellular plasticity. This is the first study to show increased numbers of proliferating cells and immature neurons in the hippocampus following touchscreen testing, and that touchscreen training can improve cognitive performance in maze-based spatial navigation tasks. This potential for touchscreen testing to induce cognitive enhancement, or other phenotypic shifts, in preclinical models should be considered in study design. Furthermore, touchscreen-mediated cognitive enhancement could have therapeutic implications for cognitive disorders.

Preconceptual paternal environmental stimulation alters behavioural phenotypes and adaptive responses intergenerationally in Swiss mice.

Experimental research has recently revealed that paternal environmental conditions can influence the offspring phenotype through epigenetic mechanisms. However, it is unclear whether these effects impact adaptive responses in the offspring. Environmental enrichment (EE) is a well-established paradigm that promotes neural plasticity. We investigated whether EE in male mice could modify behaviours that are highly relevant for determining adaptive fitness, i.e. spatial memory, attractiveness and social dominance, in the offspring of outbred mice. Male Swiss mice were housed in either EE or standard housing from post-weaning to adulthood before breeding for offspring. Their offspring were raised in standard housing until adulthood then assessed for behavioural, physiological and molecular parameters. F0 male mice exposed to EE had lower body weight, higher adrenal, spleen and hippocampal weights, better novelty processing and spatial learning, greater hippocampal BDNF levels, and higher social dominance. Unexpectedly, their male offspring (F1) showed spatial memory impairment, lowered social dominance and were less attractive to receptive females, compared to controls. These ethologically relevant measures suggest a maladaptive response in the male F1 offspring. Interestingly, when separate cohorts of male F1 offspring of standard housing or EE fathers were exposed to 8-day EE protocol during adulthood, differences in spatial memory and attractiveness to receptive females were no longer observed between them. These results provide evidence that the paternal environment can influence the offspring's adaptiveness.

Ethanol Sensitization during Adolescence or Adulthood Induces Different Patterns of Ethanol Consumption without Affecting Ethanol Metabolism.

In previous study, we demonstrated that ethanol preexposure may increase ethanol consumption in both adolescent and adult mice, in a two-bottle choice model. We now questioned if ethanol exposure during adolescence results in changes of consumption pattern using a three-bottle choice procedure, considering drinking-in-the-dark and alcohol deprivation effect as strategies for ethanol consumption escalation. We also analyzed aldehyde dehydrogenase (ALDH) activity as a measurement of ethanol metabolism. Adolescent and adult Swiss mice were treated with saline (SAL) or 2.0 g/kg ethanol (EtOH) during 15 days (groups: Adolescent-SAL, Adolescent-EtOH, Adult-SAL and Adult-EtOH). Five days after the last injection, mice were exposed to the three-bottle choice protocol using sucrose fading procedure (4% + sucrose vs. 8%-15% ethanol + sucrose vs. water + sucrose) for 2 h during the dark phase. Sucrose was faded out from 8% to 0%. The protocol was composed of a 6-week acquisition period, followed by four withdrawals and reexposures. Both adolescent and adult mice exhibited ethanol behavioral sensitization, although the magnitude of sensitization in adolescents was lower than in adults. Adolescent-EtOH displayed an escalation of 4% ethanol consumption during acquisition that was not observed in Adult-EtOH. Moreover, Adult-EtOH consumed less 4% ethanol throughout all the experiment and less 15% ethanol in the last reexposure period than Adolescent-EtOH. ALDH activity varied with age, in which older mice showed higher ALDH than younger ones. Ethanol pretreatment or the pattern of consumption did not have influence on ALDH activity. Our data suggest that ethanol pretreatment during adolescence but not adulthood may influence the pattern of ethanol consumption toward an escalation in ethanol consumption at low dose, without exerting an impact on ALDH activity.