Oxytocin administration modulates the complex type of ultrasonic vocalisation of mice pups prenatally exposed to valproic acid.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterised by communication disability with no curative treatment. Maternal separation-induced ultrasonic vocalisation (USV) was widely used to assess communication disability between pups and dams. Particularly, USV calls in many genetically modified ASD model mice were altered. Previously, we demonstrated that mice pups exposed to valproic acid in utero (VPA pups) showed decreased number of USV calls on postnatal day 11 and were rescued by subcutaneous injection of oxytocin. However, the qualitative change of USV calls by oxytocin has not been evaluated in VPA pups. In the present study, we examined the duration of oxytocin effect and analysed the altered pattern of USV calls using VPA pups. The oxytocin administration increased the total number of USV calls and the effect persisted up to 120 min in VPA pups. The pattern analysis revealed that the increase in the number of complex calls also persisted up to 120 min. These results suggested that oxytocin had a prolonged effect on USV calls, mainly on complex calls, in VPA pup, showing that oxytocin could recover their social modality to respond to maternal separation.

Increased emissions of 50-kHz ultrasonic vocalizations in hemiparkinsonian rats repeatedly treated with dopaminomimetic drugs: A potential preclinical model for studying the affective properties of dopamine replacement therapy in Parkinson's disease.

Dopamine replacement therapy used in Parkinson's disease (PD) may induce alterations in the emotional state that can underlie the manifestation of iatrogenic psychiatric-like disturbances. The preclinical investigation of these disturbances is limited, also because few reliable paradigms are available to study the affective properties of dopaminomimetic drugs in parkinsonian animals. To provide a relevant experimental tool in this respect, we evaluated whether dopaminomimetic drugs modified the emission of 50-kHz ultrasonic vocalizations (USVs), a behavioral marker of positive affect, in rats bearing a unilateral lesion with 6-hydroxydopamine in the medial forebrain bundle. Apomorphine (2 or 4 mg/kg, i.p.), L-3,4-dihydroxyphenilalanine (L-DOPA, 6 or 12 mg/kg, i.p.), or pramipexole (2 or 4 mg/kg, i.p.) were administered in a test cage (× 5 administrations) on alternate days. Seven days after treatment discontinuation, rats were re-exposed to the test cage to measure conditioned calling behavior and thereafter received a drug challenge. Hemiparkinsonian rats treated with either apomorphine or L-DOPA, but not pramipexole, markedly vocalized during repeated treatment and after challenge, and showed conditioned calling behavior. Moreover, apomorphine, L-DOPA and pramipexole elicited different patterns of 50-kHz USV emissions and rotational behavior, indicating that calling behavior in hemiparkinsonian rats treated with dopaminomimetic drugs is not a byproduct of motor activation. Taken together, these results suggest that measuring 50-kHz USV emissions may be a relevant experimental tool for studying how dopaminomimetic drugs modify the affective state in parkinsonian rats, with possible implications for the preclinical investigation of iatrogenic psychiatric-like disturbances in PD.

Long-term effects of maternal cannabis vapor exposure on emotional reactivity, social behavior, and behavioral flexibility in offspring.

The use of cannabis during pregnancy is a growing public health concern. As more countries implement legislation permitting recreational cannabis use, there is an urgent need to better understand its impact on fetal neurodevelopment and its long-term effects in exposed offspring. Studies examining effects of prenatal cannabis exposure typically employ injections of synthetic cannabinoids or isolated cannabis constituents that may not accurately model cannabis use in human populations. To address this limitation, we developed a novel e-cigarette technology-based system to deliver vaporized cannabis extracts to pregnant Long Evans rats. We used this model to determine effects of prenatal cannabis exposure on emotional, social, and cognitive endpoints of male and female offspring during early development and into adulthood. Dams were exposed to cannabis vapor (CANTHC: 400 mg/ml), vehicle vapor (VEH), or no vapor (AIR) twice daily during mating and gestation. Offspring exposed to CANTHC and VEH showed reduced weight gain relative to AIR offspring prior to weaning. CANTHC offspring made more isolation-induced ultrasonic vocalizations (USVs) on postnatal day 6 (P6) relative to VEH-exposed offspring, which is indicative of increased emotional reactivity. Male CANTHC offspring engaged in fewer social investigation behaviors than VEH-exposed male offspring during a social play test on P26. In adulthood, CANTHC-exposed offspring spent less time exploring the open arms of the elevated plus maze and exhibited dose-dependent deficits in behavioral flexibility in an attentional set-shifting task relative to AIR controls. These data collectively indicate that prenatal cannabis exposure may cause enduring effects on the behavioral profile of offspring.

Effects of nicotine, nornicotine and cotinine, alone or in combination, on locomotor activity and ultrasonic vocalization emission in adult rats.

RATIONALE: The behavioral effects of the nicotine metabolites nornicotine and cotinine have not been investigated extensively. OBJECTIVES: To evaluate the effects of nicotine, cotinine, and nornicotine, given alone or in combination, on locomotor activity and emission of ultrasonic vocalizations in male adult rats. METHODS: Rats were first given home cage nicotine injections to make them tolerant to the drug's locomotor depressant effects. On subsequent days, locomotor activity (LMA) and ultrasonic vocalizations were recorded in an open field, for 60 min after challenge injection, using repeated measures designs. In single-drug experiments, subjects were tested with nicotine 0.05-0.4 mg/kg, cotinine 0.03-3 mg/kg, or nornicotine 0.1-10 mg/kg. In drug-combination experiments, saline or nicotine 0.2 mg/kg challenge was preceded by cotinine (0, 0.3, 3 mg/kg) or nornicotine (0, 0.1, 0.3, 1, 3 mg/kg) injection. RESULTS: High doses of nornicotine increased LMA and blunted the locomotor stimulant effect of nicotine. Less consistently, nicotine and high doses of nornicotine decreased the 50-kHz call rate, with no clear evidence of a nornicotine × nicotine interaction. Cotinine, given alone or before nicotine injection, altered neither LMA nor the call rate. No drug altered the relative prevalence of flat vs. trill 50-kHz call subtypes, except that the highest dose of nornicotine promoted flat calls over trills. No drug evoked 22-kHz calls. CONCLUSION: Nornicotine can exert an acute anti-nicotine effect in vivo, as previously reported in vitro. The finding that nicotine did not detectably alter the 50-kHz call profile appears consistent with this drug's mild subjective effects in human subjects.

Treatment of electrical wrist stimulation reduces chemotherapy-induced neuropathy and ultrasound vocalization via modulation of spinal NR2B phosphorylation.

Docetaxel, a chemotherapeutic agent used to treat breast cancer, produces a robust painful neuropathy that is aggravated by mechanical and thermal stimuli. This study was undertaken to investigate the analgesic effects of electrical stimulation on docetaxel-induced neuropathic pain in mice and to identify associated changes in ultrasound vocalizations. Peripheral neuropathy was induced with intraperitoneally injected docetaxel (5 mg/kg) on 3 times every 2 days in male ICR mice. Electrical wrist stimulation was administered and pain behavior signs were evaluated by von Frey filaments and thermal stimulation on the hind paw. Ultrasound vocalizations were measured using ultrasound microphones, after electrical stimulation. After mice developed docetaxel-induced neuropathic pain behavior, an electrical stimulation temporarily attenuated mechanical allodynia and thermal hyperalgesia. In formalin and NMDA test, pain-induced mice showed increases in 10-30 kHz ultrasound vocalizations, but not in 30-50 and 50-80 kHz vocalizations. Treatment with docetaxel selectively increased 10-30 kHz ultrasound vocalizations, whereas electrical stimulation caused a meaningful decrease. Moreover, electrical stimulation suppressed the docetaxel-enhanced phosphorylation of the NMDA receptor NR2B subunit in the spinal dorsal horn. These results of the analgesic effect of electrical stimulation in chemotherapy-induced neuropathy could potentially provide a new method to treat and manage peripheral neuropathy in patients with cancer.

Oxytocin ameliorates maternal separation-induced ultrasonic vocalisation calls in mouse pups prenatally exposed to valproic acid.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder estimated by the World Health Organization to occur in one of 160 children worldwide. No pharmaceutical treatments are available to improve the deficits in social communication that are common symptoms of ASD. Recent clinical trials have focused on the nasal application of oxytocin, a neuronal peptide known to regulate a variety of social behaviours. However, the effect of oxytocin on this deficit is inconclusive. By contrast, evidence from ASD animal model studies indicates that when animals are treated with oxytocin during early development, improvements in social deficits are observed in adulthood. Thus, it is necessary to examine the effect of therapeutic target medication prescribed in early development. Mice prenatally exposed to valproic acid (VPA) are widely used as an animal model of ASD. However, many behavioural studies have been conducted during adulthood rather than early development. To establish a screening system to identify therapeutic drugs that are effective when delivered during the early postnatal period, it is important to examine the early developmental changes in their communicative behaviours. In the present study, we examined the ultrasonic vocalisation (USV) of VPA-exposed mice pups during their early postnatal developmental days. USV rates were comparable to those of the controls until the first week of their life but declined more on postnatal day 11. We checked the expression of oxytocin system in the hypothalamus and found the down-regulation of oxytocin and CD38, and up-regulation of oxytocin receptor in the VPA pups. Acute administration of oxytocin on postnatal day 11 increased the call rate of VPA pups. Taken together, we have demonstrated there was a deficiency in the oxytocinergic signalling in the VPA pups and also shown the existence of time periods that are effective with respect to screening the therapeutic drugs.

The Protective Effect of Echinochrome A on Extracellular Matrix of Vocal Folds in Ovariectomized Rats.

Here, we investigated the effects of sex hormones on extracellular matrix (ECM)-related gene expression in the vocal fold lamina propria of ovariectomized (after ovary removal) rats and verified whether echinochrome A (ECH) exerts any therapeutic effects on ECM reconstitution after estrogen deficiency in ovariectomized rats. Sprague-Dawley female rats (9 weeks old) were acclimatized for a week and randomly divided into three groups (n = 15 each group) as follows: group I (sham-operated rats, SHAM), group II (ovariectomized rats, OVX), group III (ovariectomized rats treated with ECH, OVX + ECH). Rats from the OVX + ECH group were intraperitoneally injected with ECH at 10 mg/kg thrice a week after surgery for 6 weeks. And rats were sacrificed 6 weeks after ovariectomy. Estradiol levels decreased in OVX group compared with the SHAM group. ECH treatment had no effect on the levels of estradiol and expression of estrogen receptor ß (ERß). The evaluation of ECM components showed no significant changes in elastin and hyaluronic acid levels between the different groups. Collagen I and III levels were lower in OVX group than in SHAM group but increased in OVX + ECH group. The mRNA levels of matrix metalloproteinase (MMP)-1, -2, -8, and -9 were significantly higher in the OVX group than in the SHAM group, but decreased in the OVX + ECH group. Thus, changes were observed in ECM-related genes in the OVX group upon estradiol deficiency that were ameliorated by ECH administration. Thus, the vocal fold is an estradiol-sensitive target organ and ECH may have protective effects on the ECM of vocal folds in ovariectomized rats.

Acute neuroestrogen blockade attenuates song-induced immediate early gene expression in auditory regions of male and female zebra finches.

Neuron-derived estrogens are synthesized by aromatase and act through membrane receptors to modulate neuronal physiology. In many systems, long-lasting hormone treatments can alter sensory-evoked neuronal activation. However, the significance of acute neuroestrogen production is less understood. Both sexes of zebra finches can synthesize estrogens rapidly in the auditory cortex, yet it is unclear how this modulates neuronal cell signaling. We examined whether acute estrogen synthesis blockade attenuates auditory-induced expression of early growth response 1 (Egr-1) in the auditory cortex of both sexes. cAMP response element-binding protein phosphorylation (pCREB) induction by song stimuli and acute estrogen synthesis was also examined. We administered the aromatase inhibitor fadrozole prior to song exposure and measured Egr-1 across several auditory regions. Fadrozole attenuated Egr-1 in the auditory cortex greater in males than females. Females had greater expression and clustering of aromatase cells than males in high vocal center (HVC) shelf. Auditory-induced Egr-1 expression exhibited a large sex difference following fadrozole treatment. We did not observe changes in pCREB expression with song presentation or aromatase blockade. These findings are consistent with the hypothesis that acute neuroestrogen synthesis can drive downstream transcriptional responses in several cortical auditory regions, and that this mechanism is more prominent in males.

Rapamycin blocks the neuroprotective effects of sex steroids in the adult birdsong system.

In adult songbirds, the telencephalic song nucleus HVC and its efferent target RA undergo pronounced seasonal changes in morphology. In breeding birds, there are increases in HVC volume and total neuron number, and RA neuronal soma area compared to nonbreeding birds. At the end of breeding, HVC neurons die through caspase-dependent apoptosis and thus, RA neuron size decreases. Changes in HVC and RA are driven by seasonal changes in circulating testosterone (T) levels. Infusing T, or its metabolites 5α-dihydrotestosterone (DHT) and 17 ß-estradiol (E2), intracerebrally into HVC (but not RA) protects HVC neurons from death, and RA neuron size, in nonbreeding birds. The phosphoinositide 3-kinase (PI3K)-Akt (a serine/threonine kinase)-mechanistic target of rapamycin (mTOR) signaling pathway is a point of convergence for neuroprotective effects of sex steroids and other trophic factors. We asked if mTOR activation is necessary for the protective effect of hormones in HVC and RA of adult male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii). We transferred sparrows from breeding to nonbreeding hormonal and photoperiod conditions to induce regression of HVC neurons by cell death and decrease of RA neuron size. We infused either DHT + E2, DHT + E2 plus the mTOR inhibitor rapamycin, or vehicle alone in HVC. Infusion of DHT + E2 protected both HVC and RA neurons. Coinfusion of rapamycin with DHT + E2, however, blocked the protective effect of hormones on HVC volume and neuron number, and RA neuron size. These results suggest that activation of mTOR is an essential downstream step in the neuroprotective cascade initiated by sex steroid hormones in the forebrain.

Delta-9-THC exposure during zebra finch sensorimotor vocal learning increases cocaine reinforcement in adulthood.

Zebra finches are songbirds that learn vocal patterns during a sensitive period of development that approximates adolescence. Exposure of these animals to a cannabinoid agonist during their period of sensorimotor vocal learning alters song patterns produced in adulthood. Thus, songbirds have unique value in studying developmental effects of drug exposure on a naturally learned behavior. A missing feature of this animal model has been a method to study drug reinforcement of behavior. To address this gap we have adapted place conditioning methods, used previously to determine that singing behavior is rewarding, to study cocaine reinforcement of behavior. We have found that cocaine dose-dependently reinforces both place conditioning and aversion at potencies consistent with those observed in mammalian species. Use of this place conditioning method has allowed us to determine that, when administered during periods of sensorimotor vocal learning, delta-9-THC, but not nicotine persistently increases sensitivity to cocaine through adulthood. Establishment of this method significantly expands the songbird drug exposure model, and holds promise for better appreciation of mechanisms important to sensorimotor learning that is dependent upon successful progress through sensitive periods of CNS development.

Testosterone or Estradiol When Implanted in the Medial Preoptic Nucleus Trigger Short Low-Amplitude Songs in Female Canaries.

In male songbirds, the motivation to sing is largely regulated by testosterone (T) action in the medial preoptic area, whereas T acts on song control nuclei to modulate aspects of song quality. Stereotaxic implantation of T in the medial preoptic nucleus (POM) of castrated male canaries activates a high rate of singing activity, albeit with a longer latency than after systemic T treatment. Systemic T also increases the occurrence of male-like song in female canaries. We hypothesized that this effect is also mediated by T action in the POM. Females were stereotaxically implanted with either T or with 17ß-estradiol (E2) targeted at the POM and their singing activity was recorded daily during 2 h for 28 d until brains were collected for histological analyses. Following identification of implant localizations, three groups of subjects were constituted that had either T or E2 implanted in the POM or had an implant that had missed the POM (Out). T and E2 in POM significantly increased the number of songs produced and the percentage of time spent singing as compared with the Out group. The songs produced were in general of a short duration and of poor quality. This effect was not associated with an increase in HVC volume as observed in males, but T in POM enhanced neurogenesis in HVC, as reflected by an increased density of doublecortin-immunoreactive (DCX-ir) multipolar neurons. These data indicate that, in female canaries, T acting in the POM plays a significant role in hormone-induced increases in the motivation to sing.

Abuse potential of 2-(4-iodo-2, 5-dimethoxyphenyl)N-(2-methoxybenzyl)ethanamine (25INBOMe); in vivo and ex vivo approaches.

25INBOMe ("25-I", "N-Bomb"), one of new psychoactive substances (NPSs), is being abused for recreational purpose. However, the liability for abuse or dependence has not been systematically studied yet. The objective of the present study was to evaluate rewarding and reinforcing effects of 25INBOMe using conditioned place preference (CPP) and self-administration (SA) paradigms. In addition, ultrasonic vocalizations (USVs) were measured to investigate relationships between USVs and emotional state regarding dependence on psychoactive substances. To understand molecular mechanism involved in its action, dopamine (DA) level changes were analyzed using synaptosomes extracted from the striatal region of the brain. Expression level changes of SGK1 (serum/glucocorticoid regulated kinase 1) and PER2 (period circadian protein homolog 2), two putative biomarkers for drug dependence, were also analyzed. Results showed that 25INBOMe increased both CPP (0.3 mg/kg) and SA (0.03 mg/kg/infusion) and produced higher frequencies in USVs analysis. It also increased DA levels in the striatal region and changed expression levels of SGK1 and PER2. Results of the present study suggest that 25INBOMe might produce rewarding and reinforcing effects, indicating its dependence liability. In addition, frequencies of USV might be associated with emotional state of mice induced by psychoactive substances regarding substance dependence. This is the first systemic preclinical report on the dependence liability of 25INBOMe and the first attempt to introduce a possible relationship between USVs and emotional state of mice regarding substance dependency. Further studies are needed to clarify the mechanism involved in 25INBOMe dependency and determine the usefulness of USV measurement as a method for evaluating dependence liability.

Alterations of acoustic features of 50 kHz vocalizations by nicotine and phencyclidine in rats.

Ultrasonic vocalizations are widely used to examine affective states in rats, yet relatively few studies explore the acoustic features of vocalizations, especially in relation to drug exposure, and no studies have explored alterations in acoustic features over time. The goal of this study was to examine nicotine- and phencyclidine-induced alterations of bandwidth, duration, and frequency of 50 kHz vocalizations. The minimum and maximum frequency, bandwidth, and duration of calls were examined after 7 days of daily subcutaneous administration of phencyclidine (2.0 mg/kg) and nicotine (0.2 and 0.4 mg/kg) in male Sprague-Dawley rats. Bandwidth was significantly decreased in rats treated with both nicotine (0.2 and 0.4 mg/kg) and phencyclidine. Maximum frequency was lowest on the first day of exposure compared with all other days and was not altered by drug exposure. Call duration was not affected by time or drug exposure. These findings suggest the importance of studying alterations in acoustic features in time, especially those induced by drug exposure.

Effects of ovarian hormones on the emission of 50-kHz ultrasonic vocalizations during distributed clitoral stimulation in the rat.

Fifty-kHz ultrasonic vocalizations (USVs) are emitted by adult rats during appetitive phases of behavior in response to stimuli thought to be associated with a positive affective state. In particular, 50-kHz USVs with rapid frequency oscillations, known as trills and flat-trills, in which these oscillations are flanked by a monotonic portion, are together positively correlated with appetitive behaviors such as rough and tumble play, drug and natural reward, and mating. Female rats produce 50-kHz USVs during a variety of sexual contexts, yet data are still vague as female sexual behavior is seldom studied on its own. Distributed clitoral stimulation (CLS) offers a unique approach to investigating female 50-kHz USVs as it mimics stimulation received during mating. Although CLS induces a sexual reward state, it is unknown whether CLS elicits trills and flat-trills. We addressed this question using eight ovariectomized rats, we investigated whether ovarian hormones augmented these call subtypes in response to CLS. The combined and separate effects of estradiol benzoate (EB) and progesterone (P), and oil vehicle were assessed through comparison of these call subtypes between CLS and inter-CLS interval. We found that CLS with EB + P significantly increased call duration and rate, lowered peak frequency, and widened the bandwidth of trills. Flat-trills showed a similar pattern except for call duration. Call distribution during the CLS and inter-CLS interval suggest that trill and flat-trills may be indicative of both anticipatory and sexual reward.

Committed for the long haul: Do nonapeptides regulate long-term pair maintenance in zebra finches?

The nonapeptides (oxytocin, vasopressin, and their non-mammalian homologs) regulate a number of social behaviors across vertebrates including monogamous pair bonds in mammals. Recent work on zebra finches has shown an important role for these neurohormones in establishing avian pair bonds as well. However, studies on the role of nonapeptides in maintaining pair bonds after pair formation are lacking. The goal of the present study was to investigate the effects of an oxytocin receptor antagonist (OTA) on pair maintenance behaviors in the monogamous zebra finch. I injected established zebra finch pairs over three days with either 5 µg of an OTA or a vehicle control, and separated the partners for one hour, after which partners were reunited and their reunion recorded on video for 30 min. Videos were then coded to measure singing, affiliative (allopreening, clumping, following), and aggressive (pecking) behaviors. These behaviors were also measured both on the day before injections to establish a pre-treatment level and two days after the last injection. Control and antagonist treated birds did not differ in the amount of time spent clumping or the frequency of pecking across the experiment. However, both male and female zebra finches that received OTA significantly reduced the amount of time spent following their partner. Females given the OTA treatment reduced allopreening and males given the OTA treatment reduced the frequency of singing bouts directed at their partners relative to controls. These results suggest that the nonapeptides play a role in regulating some, but not all, pair maintenance behaviors in experienced zebra finches.

NYX-2925 Is a Novel N-Methyl-d-Aspartate Receptor Modulator that Induces Rapid and Long-Lasting Analgesia in Rat Models of Neuropathic Pain.

NYX-2925 [(2S,3R)-3-hydroxy-2-((R)-5-isobutyryl-1-oxo-2,5-diazaspiro[3.4]octan-2-yl)butanamide] is a novel N-methyl-d-aspartate (NMDA) receptor modulator that is currently being investigated in phase 2 clinical studies for the treatment of painful diabetic peripheral neuropathy and fibromyalgia. Previous studies demonstrated that NYX-2925 is a member of a novel class of NMDA receptor-specific modulators that affect synaptic plasticity processes associated with learning and memory. Studies here examined NYX-2925 administration in rat peripheral chronic constriction nerve injury (CCI) and streptozotocin-induced diabetic mechanical hypersensitivity. Additionally, NYX-2925 was examined in formalin-induced persistent pain model and the tail flick test of acute nociception. Oral administration of NYX-2925 resulted in rapid and long-lasting analgesia in both of the neuropathic pain models and formalin-induced persistent pain, but was ineffective in the tail flick model. The analgesic effects of NYX-2925 were blocked by the systemic administration of NMDA receptor antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid. Microinjection of NYX-2925 into the medial prefrontal cortex of CCI rats resulted in analgesic effects similar to those observed following systemic administration, whereas intrathecal administration of NYX-2925 was ineffective. In CCI animals, NYX-2925 administration reversed deficits seen in a rat model of rough-and-tumble play. Thus, it appears that NYX-2925 may have therapeutic potential for the treatment of neuropathic pain, and the data presented here support the idea that NYX-2925 may act centrally to ameliorate pain and modulate negative affective states associated with chronic neuropathic pain.

Multigenerational effects of bisphenol A or ethinyl estradiol exposure on F2 California mice (Peromyscus californicus) pup vocalizations.

Rodent pups use vocalizations to communicate with one or both parents in biparental species, such as California mice (Peromyscus californicus). Previous studies have shown California mice developmentally exposed to endocrine disrupting chemicals, bisphenol A (BPA) or ethinyl estradiol (EE), demonstrate later compromised parental behaviors. Reductions in F1 parental behaviors might also be due to decreased emissions of F2 pup vocalizations. Thus, vocalizations of F2 male and female California mice pups born to F1 parents developmentally exposed to BPA, EE, or controls were examined. Postnatal days (PND) 2-4 were considered early postnatal period, PND 7 and 14 were defined as mid-postnatal period, and PND 21 and 28 were classified as late postnatal period. EE pups showed increased latency to emit the first syllable compared to controls. BPA female pups had decreased syllable duration compared to control and EE female pups during the early postnatal period but enhanced responses compared to controls at late postnatal period; whereas, male BPA and EE pups showed greater syllable duration compared to controls during early postnatal period. In mid-postnatal period, F2 BPA and EE pups emitted greater number of phrases than F2 control pups. Results indicate aspects of vocalizations were disrupted in F2 pups born to F1 parents developmentally exposed to BPA or EE, but their responses were not always identical, suggesting BPA might not activate estrogen receptors to the same extent as EE. Changes in vocalization patterns by F2 pups may be due to multigenerational exposure to BPA or EE and/or reduced parental care received.

Effects of acute morphine withdrawal on ultrasonic vocalizations in adult rats: unchanged 50-kHz call rate and altered subtype profile.

RATIONALE: Adult rat 22- and 50-kHz ultrasonic vocalizations (USVs) are commonly considered as indices of negative and positive affect, respectively. More specifically, we have proposed that positive affective states are revealed by a predominance of trill over flat 50-kHz call subtypes. However, the 50-kHz call subtypes emitted during aversive drug states remain largely uninvestigated. OBJECTIVES: To determine whether acute morphine withdrawal affects 50-kHz call rates or alters the relative prevalence of trill and flat calls. METHODS: In experiment 1, adult male rats were given saline or morphine (6 mg/kg SC), then acutely challenged 4 h later with saline or naloxone (1 mg/kg SC), and recorded 10-30 min post-injection. In experiments 2 and 3, rats received saline or morphine (6 mg/kg), followed 4 h later by acute saline or naloxone (0.1 mg/kg) challenge; USVs were subsequently recorded during 30-min place conditioning sessions. RESULTS: Naloxone (0.1 mg/kg) produced a strong conditioned place aversion only after acute morphine pretreatment, consistent with antagonist-precipitated morphine withdrawal. The morphine-naloxone combination decreased the relative prevalence of trills and promoted flat calls. Naloxone given alone (0.1 and 1 mg/kg) inhibited trill calls but did not significantly alter the prevalence of flat calls, whereas morphine given alone (4 h pre-session) was largely without effect. Fifty-kHz call rates were inhibited by naloxone given alone, but otherwise unaffected. Twenty-two-kHz calls were sparse. CONCLUSIONS: The 50-kHz call subtype shift seen during antagonist-precipitated morphine withdrawal was opposite in direction to that previously associated with rewards, and hence may reveal negative affect.

Neuroestrogens rapidly shape auditory circuits to support communication learning and perception: Evidence from songbirds.

Contribution to Special Issue on Fast effects of steroids. Steroid hormones, such as estrogens, were once thought to be exclusively synthesized in the ovaries and enact transcriptional changes over the course of hours to days. However, estrogens are also locally synthesized within neural circuits, wherein they rapidly (within minutes) modulate a range of behaviors, including spatial cognition and communication. Here, we review the role of brain-derived estrogens (neuroestrogens) as modulators within sensory circuits in songbirds. We first present songbirds as an attractive model to explore how neuroestrogens in auditory cortex modulate vocal communication processing and learning. Further, we examine how estrogens may enhance vocal learning and auditory memory consolidation in sensory cortex via mechanisms similar to those found in the hippocampus of rodents and birds. Finally, we propose future directions for investigation, including: 1) the extent of developmental and hemispheric shifts in aromatase and membrane estrogen receptor expression in auditory circuits; 2) how neuroestrogens may impact inhibitory interneurons to regulate audition and critical period plasticity; and, 3) dendritic spine plasticity as a candidate mechanism mediating estrogen-dependent effects on vocal learning. Together, this perspective of estrogens as neuromodulators in the vertebrate brain has opened new avenues in understanding sensory plasticity, including how hormones can act on communication circuits to influence behaviors in other vocal learning species, such as in language acquisition and speech processing in humans.

Local anaesthetic refinement of pentobarbital euthanasia reduces abdominal writhing without affecting immunohistochemical endpoints in rats.

Sodium pentobarbital is a commonly used agent for euthanizing laboratory rats, however its high pH can cause abdominal discomfort after intraperitoneal injection. Previous studies suggest that the addition of a local anaesthetic may alleviate this discomfort, but the practice has not been widely adopted. We examined the effect of combining lidocaine with pentobarbital on abdominal writhing, defecation, ultrasonic vocalizations, the rat grimace scale and immunohistochemical staining for c-Fos in the nucleus accumbens and basolateral amygdala of the brain. We also compared the amount of abdominal writhing following intraperitoneal administration of pentobarbital-lidocaine with that of pentobarbital-bupivacaine. Our results show that lidocaine reduces abdominal writhing and defecation without affecting immunohistochemistry for c-Fos or latency to loss of posture. However, scores on the rat grimace scale were low in both situations and almost no ultrasonic vocalizations were recorded. Additionally, we found that the amount of abdominal writhing was not significantly different when bupivacaine was used rather than lidocaine. Our results suggest that pentobarbital-induced euthanasia can be refined with the addition of lidocaine or other local anaesthetics.