The effect of playback of 22-kHz and 50-kHz ultrasonic vocalizations on rat behaviors assessed with a modified open-field test.

Juvenile and adult rats emit two affectively different types of ultrasonic vocalizations (USVs), namely aversive 22-kHz and appetitive 50-kHz USVs. Aversive 22-kHz USVs are considered to be alarm calls that communicate negative affective states to conspecific receivers. Although the alarming effects of playback of 22-kHz USVs were reported recently, behavioral data showing those effects are still not abundant.

The acoustic startle reflex as a tool for assessment of odor environment effects on affective states in laboratory mice.

Apart from self and conspecific odors, odors from other species also influence the affective states in laboratory mice (Mus musculus musculus) in their home cages and during experimental procedures, possibly inducing confusion and inconsistency in experimental data. Thus, it is important to detect the types of animal odors associated with housing, husbandry, and laboratory practice that can arouse different types of affective changes in mice. Here, we aimed to test the effectiveness of the acoustic startle reflex (ASR) in detecting changes in the affective states of laboratory mice due to animal-derived-odor as it has a non-zero baseline, and can be enhanced or attenuated by positive or negative affective shifts, respectively.

Lowering barometric pressure induces neuronal activation in the superior vestibular nucleus in mice.

Weather changes accompanied by decreases in barometric pressure are suggested to trigger meteoropathy, i.e., weather-related pain.

The CCR4-NOT deadenylase complex controls Atg7-dependent cell death and heart function.

Shortening and removal of the polyadenylate [poly(A)] tail of mRNA, a process called deadenylation, is a key step in mRNA decay that is mediated through the CCR4-NOT (carbon catabolite repression 4-negative on TATA-less) complex. In our investigation of the regulation of mRNA deadenylation in the heart, we found that this complex was required to prevent cell death. Conditional deletion of the CCR4-NOT complex components Cnot1 or Cnot3 resulted in the formation of autophagic vacuoles and cardiomyocyte death, leading to lethal heart failure accompanied by long QT intervals.

Changes in acoustic startle reflex in rats induced by playback of 22-kHz calls.

In aversive or dangerous situations, adult rats emit long characteristic ultrasonic calls, often termed "22-kHz calls," which have been suggested to play a role of alarm calls. Although the playback experiment is one of the most effective ways to investigate the alarming properties of 22-kHz calls, clear behavioral evidence showing the anxiogenic effects of these playback stimuli has not been directly obtained to date. In this study, we investigated whether playback of 22-kHz calls or synthesized sine tones could change the acoustic startle reflex (ASR), enhancement of which is widely considered to be a reliable index of anxiety-related negative affective states in rats.

Alarm pheromone does not modulate 22-kHz calls in male rats.

Rats are known to emit a series of ultrasonic vocalizations, termed 22-kHz calls, when exposed to distressing stimuli. Pharmacological studies have indicated that anxiety mediates 22-kHz calls in distressed rats. We previously found that exposure to the rat alarm pheromone increases anxiety in rats.

Air puff-induced 22-kHz calls in F344 rats.

Air puff-induced ultrasonic vocalizations in adult rats, termed "22-kHz calls," have been applied as a useful animal model to develop psychoneurological and psychopharmacological studies focusing on human aversive affective disorders. To date, all previous studies on air puff-induced 22-kHz calls have used outbred rats. Furthermore, newly developed gene targeting technologies, which are essential for further advancement of biomedical experiments using air puff-induced 22-kHz calls, have enabled the production of genetically modified rats using inbred rat strains.

Temporary inactivation of the anterior part of the bed nucleus of the stria terminalis blocks alarm pheromone-induced defensive behavior in rats.

Rats emit an alarm pheromone in threatening situations. Exposure of rats to this alarm pheromone induces defensive behaviors, such as head out behavior, and increases c-Fos expression in brain areas involved in the mediation of defensive behaviors. One of these brain areas is the anterior bed nucleus of the stria terminalis (aBNST).

The emission of stress-induced 22-kHz calls in female rats is independent of testosterone levels.

Although emission of ultrasonic calls in rats induced by stress, referred to as "22-kHz calls," is dependent on circulating testosterone levels in males, it is still unknown whether the same testosterone-based regulation is applicable to female rats. In this study, we investigated the sex difference in the emission of air-puff-induced 22-kHz calls in rats on the basis of the hypothesis that female rats would emit fewer 22-kHz calls, and assessed whether male-like circulating testosterone levels can also influence the emission of 22-kHz calls in females. The experimental results showed that female rats emit significantly fewer 22-kHz calls than male rats.

Identification of a pheromone that increases anxiety in rats.

Chemical communication plays an important role in the social lives of various mammalian species. Some of these chemicals are called pheromones. Rats release a specific odor into the air when stressed.

Relationship between 22-kHz calls and testosterone in male rats.

Ultrasonic calls in rats induced by the presence of a predator, referred to as "22-kHz calls," are mainly emitted by socially dominant male rats. Testosterone levels are closely related to social dominance in male rats. In the present study, we investigated the relationship between the emission of stress-induced 22-kHz calls and circulating testosterone levels in male rats, using a combination of surgery (castration or sham operation) and chronic steroid administration (testosterone or cholesterol) to modify circulating testosterone levels.

Effect of post-weaning individual housing on autonomic responses in male rats to sexually receptive female rats.

Post-weaning individual housing induces significant alterations in the reward system of adult male rats presented with sexually receptive female rats. In this study, we examined the effects of post-weaning individual housing on autonomic nervous activity in adult male rats during encounters with sexually receptive female rats to assess whether different affective states depending on post-weaning housing conditions are produced. Changes in heart rate and spectral parameters of heart rate variability indicated that in post-weaning individually housed male rats, both sympathetic and parasympathetic activity increased with no change in the sympathovagal balance, while in post-weaning socially housed male rats, both sympathetic and parasympathetic activity decreased with a predominance of parasympathetic activity.

The effect of post-weaning individual housing on 50-kHz calls emitted from male rats to sexually receptive female rats.

Post-weaning individual housing induces significant alterations in the social behaviors of laboratory rats. Adult rats use ultrasonic vocalizations as a primary method to communicate social affective states. In this study, we examined the effect of prolonged post-weaning individual housing on the emission of male ultrasonic vocalizations referred to as "50-kHz calls", which are positively correlated with positive and social affective states in adult male rats.

The critical point at which post-weaning individual housing conditions affect the emission of 22-kHz calls in male rats.

It is known that long-term post-weaning individual housing significantly reduces emissions of 22-kHz calls in male rats. In this study, we assessed post-weaning successive changes in 22-kHz calls emitted by male rats under two different types of post-weaning housing conditions (individually and socially). In addition, we evaluated the critical point at which a significant reduction in 22-kHz calls could be observed in male rats housed individually after weaning.

Close relationship between the frequency of 22-kHz calls and vocal tract length in male rats.

It is known that the size of the components of the sound production apparatus in mammals may affect the acoustic structure of vocalizations. Therefore, some acoustic variables such as voice frequency may change with age in association with body size and body weight increases. However, whether this relationship also applies to ultrasonic vocalizations emitted by laboratory rats has not been investigated.

Male rats respond to their own alarm pheromone.

Pheromones are defined as substances released from an individual (donor) that influence a second individual (recipient) of the same species. However, it is unclear whether mammalian pheromones can affect the donor itself. To address this question, the effect of self-exposure to an alarm pheromone was examined.

Effects of slightly acidic electrolysed drinking water on mice.

Slightly acidic electrolysed (SAE) water is a sanitizer with strong bactericidal activity due to hypochlorous acid. We assessed the safety of SAE water as drinking water for mice at a 5 ppm total residual chlorine (TRC) concentration to examine the possibility of SAE water as a labour- and energy-saving alternative to sterile water. We provided SAE water or sterile water to mice for 12 weeks, during which time we recorded changes in body weight and weekly water and food intakes.

Discovery, optimization, and pharmacological characterization of novel heteroaroylphenylureas antagonists of C-C chemokine ligand 2 function.

Through the application of TRAP (target-related affinity profiling), we identified a novel class of heteroaroylphenylureas that inhibit human CCL2-induced chemotaxis of monocytes/macrophages both in vitro and in vivo. This inhibition was concentration-dependent and selective with regard to other chemokines. The compounds, however, did not antagonize the binding of (125)I-labeled CCL2 to the CCR2 receptor nor did they block CCR2-mediated signal transduction responses such as calcium mobilization.

The effect of vapor of propylene glycol on rats.

Propylene glycol (PG) is commonly used as a solvent for odorous chemicals employed in studies of the olfactory system because PG has been considered to be odorless for humans and other animals. However, if laboratory rats can detect the vapor of PG and if exposure to this influences behaviors, such effects might confound data obtained from experiments exposing conscious rats to odorants dissolved in PG. Therefore, we examined this issue using differences in the acoustic startle reflex (ASR) as an index.

The alarm pheromone in male rats as a unique anxiety model: psychopharmacological evidence using anxiolytics.

Previously, we demonstrated that an alarm pheromone released from male donor Wistar rats evoked anxiety-related physiological and behavioral responses in recipient rats. Thus, we believe that this pheromone may increase anxiety levels in rats. In the current study, we evaluated the predictive validity of this alarm pheromone-induced anxiogenic effect in detail by investigating whether six types of human anxiolytics, each of which has a different mechanism of action, were efficacious in reducing anxiety, using changes in the acoustic startle reflex (ASR) as an index.

The volatility of an alarm pheromone in male rats.

The volatility of an alarm pheromone in male rats. PHYSIOL BEHAV 00(0) 000-000, 2008. We previously reported that an alarm pheromone released from the perianal region of male rats is perceived by the vomeronasal organ and evokes stress-induced hyperthermia and defensive and risk assessment behavior.

Enhancement of the acoustic startle reflex by an alarm pheromone in male rats.

Recently, we reported that an alarm pheromone released from the perianal region of male rats aggravated stress-induced hyperthermia and increased defensive and risk assessment behaviors in recipient male rats. Based on these results, we hypothesized that the primary effect of the alarm pheromone is to increase anxiety; however, there is still no clear evidence for this pheromone effect. Therefore, we examined this issue by assessing the effect of the alarm pheromone on the acoustic startle reflex (ASR), which is a useful index for studying negative emotions such as anxiety in rats.

Changes in autonomic control of heart associated with classical appetitive conditioning in rats.

The aim of this study was to examine the changes in autonomic control of the heart associated with classical appetitive conditioning in rats. We trained rats to learn that a movement into a test chamber was followed by delivery of reward (contextual conditioning) and performed power spectral analysis of heart rate variability from electrocardiograms recorded using the telemetry system. We investigated the sympathovagal balance of autonomic regulation of the heart in response to not only the conditioned stimulus (the movement into the test chamber), but also the unconditioned stimulus (reward), and compared the results of these two kinds of emotional states; it might be considered that "the reward-expecting state" is evoked by the conditioned stimulus and "the reward-receiving state" is evoked by the unconditioned stimulus in rats.

The influence of social environmental condition on the production of stress-induced 22 kHz calls in adult male Wistar rats.

Adult rats emit 22 kHz ultrasonic vocalizations (USVs) in response to aversive stimuli, and these sounds are suggested to have communicative information among conspecifics. It is conceivable that social environment during development of rats has relevance to the emission of 22 kHz USVs. To examine the effects of social environment after weaning on production of stress-induced USVs, we compared the amount of emission of USVs among three groups of rats reared under different conditions after weaning.

Effects of psychological stress on autonomic control of heart in rats.

The aim of this study was to examine the effects of psychological stress on autonomic control of the heart in rats. For this purpose, we evoked anxiety-like or fear-like states in rats by means of classical conditioning and examined changes in autonomic nervous activity using an implanted telemetry system and power spectral analysis of heart rate variability. Anxiety-like states resulted in a significant increase in heart rate (HR), low frequency (LF) power, and LF/HF ratio, with no change in high frequency (HF) power.