ACTH-induced excessive grooming in the rat: the influence of environmental and motivational factors

Striatal ensemble activity in an innate naturalistic behavior

Self-grooming is an innate, naturalistic behavior found in a wide variety of organisms. The control of rodent grooming has been shown to be mediated by the dorsolateral striatum through lesion studies and in-vivo extracellular recordings. Yet, it is unclear how populations of neurons in the striatum encode grooming. We recorded single-unit extracellular activity from populations of neurons in freely moving mice and developed a semi-automated approach to detect self-grooming events from 117 hours of simultaneous multi-camera video recordings of mouse behavior. We first characterized the grooming transition-aligned response profiles of striatal projection neuron and fast spiking interneuron single units. We identified striatal ensembles whose units were more strongly correlated during grooming than during the entire session. These ensembles display varied grooming responses, including transient changes around grooming transitions or sustained changes in activity throughout the duration of grooming. Neural trajectories computed from the identified ensembles retain the grooming related dynamics present in trajectories computed from all units in the session. These results elaborate striatal function in rodent self-grooming and demonstrate that striatal grooming-related activity is organized within functional ensembles, improving our understanding of how the striatum guides action selection in a naturalistic behavior.

Melanocortin-4 receptor signaling in the central amygdala mediates chronic inflammatory pain effects on nociception

Chronic inflammatory pain represents one of the largest subsets of chronic pain diagnoses, which affect nearly a quarter of individuals in the United States and cost nearly $600 billion dollars annually. Chronic pain leads to persistent sensory hypersensitivities, as well as emotional and cognitive disturbances. Evidence suggests that melanocortin 4 receptors (MC4Rs) mediate pain-signaling and pain-like behaviors via actions at various nodes in the pain-neural axis, but the field lacks a complete understanding of the potential role of MC4Rs in chronic inflammatory pain in males and females. The central amygdala (CeA) expresses high quantities of MC4R and receives pain-related information from the periphery, and in vivo CeA manipulations alter nociceptive behavior in pain-naïve and in animals with chronic pain. Here, we tested the hypothesis that MC4Rs in the CeA modulate thermal nociception and mechanical sensitivity, as well as pain avoidance, in male and female Wistar rats, using a model of chronic inflammatory pain (Complete Freud's Adjuvant; CFA). First, we report that CFA produces long-lasting hyperalgesia in adult male and female Wistar rats, and long-lasting pain avoidance in male Wistar rats. Second, we report that MC4R antagonism in the CeA reduces thermal nociception and mechanical sensitivity in male and female Wistar rats treated with CFA. Finally, we report that MC4R antagonism in the CeA reduces pain avoidance in male, and that this effect is not due to drug effects on locomotor activity. Our results indicate that a model of chronic inflammatory pain produces long-lasting increases in pain-like behaviors in adult male and female Wistar rats, and that antagonism of MC4Rs in the CeA reverses those effects.

Altering the development of the dopaminergic system through social play in rats: Implications for anxiety, depression, hyperactivity, and compulsivity

Dopamine is essential to many functions like reward, motivation, and attention; when its neural pathways do not function properly, various disorders (e.g., anxiety, depression, hyperactivity, compulsions) can arise. Truncated-DAT rats display persistent stereotypies and aggressiveness; hence they are a new valuable animal model to study the pathogenesis of these disorders. The focus of research is often on the individual epigenetic determinants and much less on the impact of social experiences. Here, we investigate the developmental impact of the social environment on adolescent wild type (WT) rats. We divided subjects at weaning into three groups: living with another adolescent (WT Peer), with a WT adult, or with a truncated-DAT one, and we observed homecage social behavior of these pairs (play, jump, victory, and "bullying") during whole adolescence. When adult, we observed the same subjects in plus maze, forced swim, and social preference tests to measure levels of anxiety, depression, and quality of social interactions. Compared to the other groups, WT rats that had spent their adolescence with a truncated-DAT adult as companion show more anxious, depressive, hyperactive, impulsive, and compulsive behaviours. Results confirm that social interactions and healthy play (i.e., when play has behavioural, social, and psychomotor rewards that support the cognitive, emotional and physical development of the individual) are essential to neurobehavioral maturation. Conversely, anomalous interactions like poor play and "bullying" in developing rats may impact onto their dopaminergic system. Consequently, an impoverished social play could be one of the factors contributing to the appearance of putative indexes of attention deficit hyperactivity disorder (ADHD) and\or obsessive-compulsive disorder (OCD).

BDNF Overexpression in the Ventral Hippocampus Promotes Antidepressant- and Anxiolytic-Like Activity in Serotonin Transporter Knockout Rats

BDNF plays a pivotal role in neuroplasticity events, vulnerability and resilience to stress-related disorders, being decreased in depressive patients and increased after antidepressant treatment. BDNF was found to be reduced in patients carrying the human polymorphism in the serotonin transporter promoter region (5-HTTLPR). The serotonin knockout rat (SERT^-/-) is one of the animal models used to investigate the underlying molecular mechanisms of depression in humans. They present decreased BDNF levels, and anxiety- and depression-like behavior. To investigate whether upregulating BDNF would ameliorate the phenotype of SERT^-/- rats, we overexpressed BDNF locally into the ventral hippocampus and submitted the animals to behavioral testing. The results showed that BDNF overexpression in the vHIP of SERT^-/- rats promoted higher sucrose preference and sucrose intake; on the first day of the sucrose consumption test it decreased immobility time in the forced swim test and increased the time spent in the center of a novel environment. Furthermore, BDNF overexpression altered social behavior in SERT^-/- rats, which presented increased passive contact with test partner and decreased solitary behavior. Finally, it promoted decrease in plasma corticosterone levels 60 min after restraint stress. In conclusion, modulation of BDNF IV levels in the vHIP of SERT^-/- rats led to a positive behavioral outcome placing BDNF upregulation in the vHIP as a potential target to new therapeutic approaches to improve depressive symptoms.

Vertical exposition to Luffa operculata extract deregulates behavior and hypothalamus neurotransmitters in juvenile rats

ETHNOPHARMACOLOGICAL RELEVANCE

Luffa operculata (L.) Cogn (Cucurbitaceae) is a traditional plant popularly used in the abortion induction, against sinusitis and is toxic.

AIM OF THE STUDY

To verify the influence of the aqueous extract obtained from the dry fruit of L. operculata (BNE) on the male rats vertically exposed to a subabortive dose of BNE, by evaluating alterations in behavior and neurochemical features in hypothalamus, striatum and frontal cortex, at a juvenile age, after receiving a stress challenge given by the use of the "New York subway stress" technique (NYS).

MATERIALS AND METHODS

Pregnant female rats (F0 generation) received 1.0 mg/kg BNE, or distilled water (100 mL/kg), by gavage, between gestation days GD17 and GD21. The pups were weaned at PND21 and were kept up to PND60 (juvenile age) in controlled environmental conditions. Four groups were obtained: control (CG), experimental (EG), stress control (SCG) and stress experimental (SEG) After being stressed, the animals were behavioral screened for in the open field (OF) and in light-dark box (LDB) apparatuses. They were euthanized, and the liver, kidneys and brain were removed for both macroscopic and microscopic analyses, and for quantification of vanillylmandelic acid (VMA), norepinephrine (NE), dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC) and the serotonin (5-HT) and its metabolite 5-hydroxyindolylacetic acid (5-HIAA) were accessed in the hypothalamus, frontal cortex and striatum.

RESULTS AND DISCUSSION

although most of the behavior changes were due to the stress challenge, the rats spent more time in the dark side of the LDB and were less likely to explore the light side, indicating that the treatment with BNE induced to fear. Interferences of BNE over behavior were due to impairment of VMA, NE, 5-HT and DA and increasing of DOPAC in the hypothalamus, and an increase of 5-HIAA in the frontal cortex, indicating alterations in the hypothalamic-hypophysis-adrenal axis (HHAA). No macroscopic or histopathological changes were observed in the liver, kidneys, or brain, although GFAP was diminished in the SCG, as expected for stressed rats.

CONCLUSION

the vertical exposition of juvenile rats to BNE led to the manifestation of fear and to a down regulation of the hypothalamic-hypophysis-adrenal axis.

The Role of Melanocortin Plasticity in Pain-Related Outcomes After Alcohol Exposure

The global COVID-19 pandemic has shone a light on the rates and dangers of alcohol misuse in adults and adolescents in the US and globally. Alcohol exposure during adolescence causes persistent molecular, cellular, and behavioral changes that increase the risk of alcohol use disorder (AUD) into adulthood. It is established that alcohol abuse in adulthood increases the likelihood of pain hypersensitivity and the genesis of chronic pain, and humans report drinking alcohol to relieve pain symptoms. However, the longitudinal effects of alcohol exposure on pain and the underlying CNS signaling that mediates it are understudied. Specific brain regions mediate pain effects, alcohol effects, and pain-alcohol interactions, and neural signaling in those brain regions is modulated by neuropeptides. The CNS melanocortin system is sensitive to alcohol and modulates pain sensitivity, but this system is understudied in the context of pain-alcohol interactions. In this review, we focus on the role of melanocortin signaling in brain regions sensitive to alcohol and pain, in particular the amygdala. We also discuss interactions of melanocortins with other peptide systems, including the opioid system, as potential mediators of pain-alcohol interactions. Therapeutic strategies that target the melanocortin system may mitigate the negative consequences of alcohol misuse during adolescence and/or adulthood, including effects on pain-related outcomes.

Pharmacological evaluation of the hydro-alcoholic extract of Campomanesia phaea fruits in rats

Campomanesia phaea (Myrtaceae), popularly known as cambuci, is one of several species of plants producing comestible fruits, largely used in human nutrition. Despite its consumption and economic potential, limited scientific research is available on the Campomanesia, especially those related to its therapeutic benefits. It is reported by traditional medicine the use of the plant in the treatment of different disorders, such as cardiovascular and nervous system disturbances. So, the aim of this study was to carry out the pharmacological evaluation of the hydro-alcoholic extract (HAE) of Campomanesia fruits in rats by screening consisting of tests: a) neuropharmacological observation, b) test on the cardiovascular system. The HAE, prepared from the extraction of fruits with water/ethanol, was concentrated and freeze-dried. Behavioral responses in rats were investigated in open field test and the cardiovascular actions were investigated by a register of indirect blood pressure and the register of spontaneous beating rate right atrium. The results revealed that HAE induced grooming, hypotension and bradycardia. So, this study identified an action on the central nervous system, represented by grooming, and a cardiovascular activity of Campomanesia. The hypotension, attributed in part to bradycardia, was not related to a cholinergic effect, discarding a possible cholinomimetic action of the plant that could justify both cardiovascular and central actions.

CNS Safety Screening Under ICH S7A Guidelines Requires Observations of Multiple Behavioral Units to Assess Motor Function

In the adoption of behavior as a critical end point in safety pharmacology and neurotoxicity screening, federal regulatory agencies have shifted the predominating scientific perspective from pharmacology back to the experimental analysis of behavior (psychology). Nowhere is this more evident than in tier I safety assessment of the central nervous system (CNS). The CNS and peripheral nervous system have multiple behavioral units of general activity. A complete picture of the motor control neural pathways cannot be measured by any one single approach. The CNS safety protocols under International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use S7A are required to be conducted in accordance with Good Laboratory Practices by trained technical staff. The CNS safety assessments necessitate the inclusion of a thorough and detailed behavioral analysis of home cage activity, the response to handling, and transportation to and observations within an open-field apparatus with ancillary measures of basal muscle tone, muscle strength, and tremor in a functional observation battery, as well as quantitative measurements of 3-dimensional activity in an automated photobeam arena. Cost-cutting initiatives or a radical application of the "reduce use" principle of the 3 Rs only jeopardize the spirit, intent, and predictive validity of tier I safety testing assays dictated by current drug safety guidelines.

Subchronic administration of creatine produces antidepressant-like effect by modulating hippocampal signaling pathway mediated by FNDC5/BDNF/Akt in mice

Creatine has been shown to play a significant role in the pathophysiology and treatment of major depressive disorder (MDD) in preclinical and clinical studies. However, the biological mechanisms underlying its antidepressant effect is still not fully elucidated. This study investigated the effect of creatine (p.o.) administered for 21 days in the behavior of mice submitted to tail suspension test (TST), a predictive test of antidepressant activity. Creatine reduced the immobility time in the TST (1-10 mg/kg), without affecting locomotor activity, a finding consistent with an antidepressant profile. Creatine administration increased the ubiquitous creatine kinase (uCK) and creatine kinase brain isoform (CK-B) mRNA in the hippocampus of mice. Taking into account that PGC-1α induces FNDC5/irisin expression mediating BDNF-dependent neuroplasticity, the effect of creatine administration (1 mg/kg, p. o.) on the hippocampal PGC-1α, FNDC5 and BDNF gene expression was investigated. Creatine treatment increased PGC-1α, FNDC5 and BDNF mRNA in the hippocampus as well as BDNF immunocontent. The involvement of BDNF downstream intracellular signaling pathway mediated by Akt, proapoptotic proteins BAX and BAD and antiapoptotic proteins Bcl2 and Bcl-xL was also investigated following creatine treatment. Creatine increased Akt phosphorylation (Ser 473), and Bcl2 mRNA and protein levels, and Bcl-xL mRNA, whereas BAD mRNA was decreased following creatine administration in the hippocampus. Altogether these results indicate that creatine antidepressant-like effect may be dependent on Akt activation and increased expression of the neuroprotective proteins in the hippocampus of mice. The obtained data reinforce the antidepressant property of creatine and highlight the role of these molecular targets in the pathophysiology of MDD.

Environmental Enrichment in Kennelled Pit Bull Terriers (Canis lupus familiaris)

Simple Summary

Rescue shelters, although set-up with good intentions, may lead to poor welfare of the animals that they house, especially when the shelter organisation is under-resourced. This study therefore investigated the behavioural effects of cheap and locally accessible objects added to the cages of rescued Pit Bull Terrier type dogs in the Philippines to determine whether it is possible for shelter organisations with limited funds and staffing to improve the welfare of their dogs with minimal additional pressure on their time and financial budgets. The addition of enrichment (coconuts; cardboard bed; or cardboard partition) to the dogs’ kennels positively affected their behavior but no one treatment was better at achieving this result. The results therefore suggest that it is possible for under-resourced rescue shelters to use cheap, locally available objects to improve the welfare of dogs in their care.

Abstract

Although social enrichment can be considered beneficial in helping dogs cope with the kennel environment, when taking individual needs into account, it places a large demand on the carers and may not be appropriate in under-resourced kennels. Some kennels are also designed in such a way that there is too much social interaction, in that individuals cannot choose to distance themselves from conspecifics. This study therefore aimed to assess the effects of easily accessible enrichment on the behaviour of kennelled Pit Bull Terrier type dogs rescued from a dog-fighting ring in the Philippines. Thirty-six dogs were allocated to one of three treatment groups following a matched-subject design: (i) cardboard bed provision; (ii) coconut provision; and (iii) visual contact with dogs housed in adjacent cages obstructed with cardboard partitions. Behavioural diversity and the duration and frequency of individual behaviours were analysed using linear mixed-effect models. Yawning frequencies and time spent lying down and sitting decreased during treatment. No particular treatment was more influential in these behavioural changes. In conclusion, enrichment, regardless of type, affected the dogs’ behaviour, with some effects depending on the sex of the dogs. Therefore, it is possible to cheaply and sustainably enrich the lives of dogs living in highly constrained environments, however, further research is required to refine the methods used.

Self-grooming induced by sexual chemical signals in male root voles (Microtus oeconomus Pallas)

Sniffing is one-way animals collect chemical signals, and many males self-groom when they encounter the odor of opposite-sex conspecifics. We tested the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles (Microtus oeconomus Pallas). Specifically, we investigated the sniffing pattern of male root voles in response to odors from the head, trunk, and tail areas of lactating and non-lactating females. The self-grooming behavior of males in response to female individual odorant stimuli was documented, and the relationship between self-grooming and sniffing of odors from the head, trunk, and tails areas were analyzed. Sniffing pattern results showed that males are most interested in odors from the head area, and more interested in odors from the tail as compared to the trunk area. Males displayed different sniffing and self-grooming behaviors when they were exposed to odors from lactating females as compared to non-lactating females. Males also spent more time sniffing and engaged in more sniffing behaviors in response to odors from the lactating females' tail area as compared to the same odors from non-lactating females. Similarly, males spent more time self-grooming and engaged in more self-grooming behaviors in the presence of individual odors from lactating females as compared to individual odors from non-lactating females. Partial correlation analyses revealed that the frequency of self-grooming was significantly correlated with the frequency of tail area sniffs. Results from this experiment suggest that sexual attractiveness of lactating females is stronger than that of non-lactating females. Furthermore, the partial correlation analysis demonstrated that self-grooming in males is induced by odors from the tail area of females. Collectively, these results support the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles. Self-grooming may also reflect the groomer's sexual motivation and facilitate sexual interactions.

Repeated subchronic exposure to phencyclidine elicits excessive atypical grooming in rats

Self-grooming in rodents is stereotypically sequenced and naturally occurs after arousal, novelty, or stress. Grooming expression and syntax resulting from stressful and appetitive conditions were assessed in male Long Evans rats treated daily with 10mg/kg of phencyclidine (PCP) for 15 days. Approximately 20 h after the 1st, the 8th, and/or the 15th injection, grooming was induced with water sprays, a loud sound, or smearing food. Behaviors expressed during the seconds or minutes that followed induction were videotaped and codified. Results showed that subchronic treatment with PCP amplified the grooming response in all stressful and appetitive conditions, but provoked a disorganization of grooming sequences only under the stressful, water condition. Thus, PCP enhanced grooming expression indiscriminately. However, this behavior had to serve both hygienic and stress managing purposes in order for chain sequencing to become disorganized as a consequence of drug treatment. These results suggest that the detailed examination of grooming expression and organization is an appropriate tool to measure stress-induced behavioral sensitization and motor functions in animal models of neuropsychiatric disorders such as schizophrenia.

Corticotropin-releasing factor-1 receptors in the basolateral amygdala mediate stress-induced anorexia

Corticotropin-releasing factor (CRF) receptor activation within the basolateral amygdala (BLA) has been relatively unexplored compared with the central nucleus of the amygdala (CeA), despite the fact that CRF receptors are more densely distributed in BLA than in CeA. The authors show that infusion of CRF into BLA, but not CeA, decreases feeding and increases grooming. These effects are mediated by CRF-sub-1 receptors, because they are blocked by intra-BLA treatment with NBI27914 (NBI), a CRF-sub-1 antagonist, but not Astressin 2B, a CRF-sub-2 antagonist. Exposure to a stressor results in behaviors identical to those seen after intra-BLA CRF infusion. These stress-induced changes are prevented by pre-stress treatment with NBI but not Astressin 2B. These data demonstrate that stimulation of intra-BLA CRF-sub-1 receptors is both necessary and sufficient for eliciting stress-induced anorexia and grooming.

Enhanced motivation to self-administer cocaine is predicted by self-grooming behaviour and relates to dopamine release in the rat medial prefrontal cortex and amygdala

Rats, like humans, show strong individual differences in their response to anxiogenic and stressful stimuli. In the present study we evaluated whether differences in stress-induced self-grooming behaviour may predict an individual's vulnerability to engage in drug self-administration behaviour. From a population of Wistar rats, the lower and upper quartile with respect to time spent self-grooming on an elevated plus maze (EPM) were selected and trained to intravenously self-administer cocaine under fixed and progressive ratio schedules of reinforcement. High grooming (HG) rats reached considerably higher breakpoints than low grooming (LG) rats but showed no differences in acquisition rate and dose-response relationships. Further, EPM exposure elicited higher anxiety levels and enhanced plasma corticosterone secretion in HG rats. In addition, HG rats did not display enhanced novelty-seeking and still spent more time self-grooming during an EPM re-test following the cocaine self-administration procedure, indicating that stress-induced self-grooming is a stable behavioural trait marker. Neurochemically, electrically evoked [(3)H]dopamine release in vitro was profoundly lower in brain slices from the substantia nigra, medial prefrontal cortex and amygdala of naive HG rats as compared to LG rats, whereas no differences were found in the nucleus accumbens shell and core, the ventral tegmental area and caudate putamen. In conclusion, stress-induced self-grooming specifically predicts enhanced motivation to self-administer cocaine rather than sensitivity to its reinforcing effects. Responsiveness of dopaminergic nerve terminals in the medial prefrontal cortex and amygdala may represent pre-existing underlying factors.

Trigeminal lesions and maternal behavior in Norway rats: III. Experience with pups facilitates recovery

In lactating rats, upper snout desensitization by trigeminal denervation severely impairs maternal behavior, with substantial recovery 12-24 hr later. The potential effects of interaction with pups on this recovery was investigated. Dams were subjected to bilateral infraorbital denervation or sham surgery on Day 5 postpartum and observed for 30 min with 6 foster pups 24 hr later, after separation from pups for 4 or 24 hr. Long separation reduced likelihood of retrieval and nursing behavior, infraorbital denervation reduced duration of pup licking, and these deprivations combined greatly increased latencies of pup sniffing and durations of facial self-grooming. Both conditions, and especially their combination, prolonged retrieval duration, the retrieval sequence being interrupted by other pup contact, such as licking. Thus, interaction with pups and adequate trigeminal stimulation maintain normal maternal behavior. These findings are possibly relevant to the normal decline of maternal responsiveness during late lactation and to other lesion-induced deficits.

Paternal alcohol consumption affects grooming response in rat offspring

Grooming behavior in response to novelty and water immersion was examined in rat offspring sired by males consuming liquid alcohol diets containing 35%, 17.5% or 0% ethanol-derived calories (EDC). In the first study, offspring were tested at 35-38 days of age under conditions of lights on or off. Offspring in the 35% EDC group groomed less than controls. Lighting conditions did not affect grooming significantly. In the second study, animals were immersed in a water bath for 15 seconds and were then placed in the same observation chambers. As in the previous study, animals sired by alcohol-consuming fathers groomed considerably less than controls. These results were interpreted as suggesting offspring sired by alcohol-consuming fathers have a blunted response to conditions which spontaneously elicit behavior like grooming or ambulation.

Perioral anesthesia disrupts maternal behavior during early lactation in Long-Evans rats

The role of perioral somatosensory stimulation from pups in maternal behavior was investigated in lactating Long-Evans rats (Rattus norvegicus) during early lactation by local anesthesia of the mystacial pads with lidocaine, which blocks conduction in the infraorbital nerve. It was concluded that (1) acute perioral anesthesia markedly inhibited pup retrieval when the subjects had no formal pretreatment retrieval experience. Further, these dams displayed little tolerance to the lidocaine treatment when they were tested repeatedly. (2) The severity of the effects of perioral anesthesia on retrieval was dependent upon prior experience and the testing situation. Following pretreatment retrieval experience, and in a test cage with dark and light compartments which provided a strong incentive to retrieve, 80% of lidocaine-injected dams did retrieve. However, retrieval efficiency was impaired by perioral anesthesia, largely due to increased time in contact with pups prior to each retrieval and to increased carrying time. (3) Perioral anesthesia also inhibited pup licking, but not self-grooming, suggesting that the former, but not the latter, is largely under peripheral stimulus control and that deficits in maternal oral activities cannot be due to impairment of mouth opening and use. (4) The onset of nursing behavior was delayed until after the recovery of snout sensations and retrieval. This suggests that a maternal behavior not directly involving the mouth is nonetheless dependent upon the dam's receipt of perioral tactile input from pups.

Altered grooming responses to stress in rats exposed prenatally to ethanol

The effects of prenatal alcohol exposure on grooming, locomotion, and rearing in response to stress were examined in adult rats whose mothers consumed a liquid diet containing 35% ethanol-derived calories (EDC). Offspring of both pair-fed 0% EDC mothers and ad libitum chow-fed mothers were included as controls. In Experiment 1, females groomed more than males following placement into a novel test chamber, but no differences due to prenatal treatment were observed. Ethanol-exposed animals groomed more than controls following the stress of a forced 1-min swim (Experiment 2), but when rats tested in Experiment 1 were observed again after forced swim stress (Experiment 3), no differences due to prenatal treatment or sex were observed. Experiment 4 examined the effects of pretreatment with 1 mg/kg naloxone on novelty-induced grooming and as in Experiment 1 prenatal treatment did not affect grooming responses. Females again groomed significantly more than males and naloxone reduced grooming equally for all groups. The results suggest that novelty-induced grooming is a sex-influenced behavior, with females grooming more than males, and that animals exposed prenatally to alcohol and tested as adults may have altered responses to certain stressors (i.e., forced swim) under specific conditions. The altered grooming response of alcohol-exposed rats to swim stress can be eliminated by preexposing them to novelty stress.

Sex differences in self-grooming of rats: effects of gonadal hormones and context

When prepubescent males and females were placed alone in a novel cage, males were found to groom their genitals, but not other body regions, more than females. This sex difference was present in untreated and in testosterone-treated gonadectomized rats as well as in intact rats. Neither the presence of gonads nor testosterone treatment affected grooming in this context. However, when similarly treated rats of the same age were observed in groups in the home cage, no sex difference in genital grooming of intact or gonadectomized rats was found. Testosterone significantly increased nongenital grooming in both sexes and genital grooming in males. Thus, both the presence of sex differences and the effects of testosterone on self-grooming depend on the behavioral context.

REM sleep deprivation decreases the grooming and shaking behaviour induced by enkephalinase inhibitor or opiate withdrawal

Intraventricular administration of enkephalinase inhibitor, phosphoramidon (1 X 10(-8)-5.6 X 10(-7) moles ICV) induced a behavioural syndrome consisting of excessive grooming with the body scratching as the most prominent symptom and wet-dog-shakes (WDS). The frequency of the phosphoramidon-induced WDS and body scratching were decreased by the pretreatment with the opiate receptor blocking agent, naltrexone (2.9 X 10(-6) moles/kg IP). Both the phosphoramidon-induced WDS in naive rats and naloxone-precipitated withdrawal WDS were decreased in REM sleep deprived rats compared with animals allowed normal sleep (control and stress groups). The results are discussed in light of a possible functional insufficiency of endorphinergic system during REMSD. It has been suggested that this insufficiency might be a background to the increased neuronal excitability during REMSD.

Increased novelty-induced grooming in aged rats: a preliminary observation

Age-related changes in grooming activity in female Fischer-344 rats were observed in a home cage and in a novel testing chamber for 50 min. Compared to the home cage condition with brief handling treatment, excessive grooming was found in the novel situation. The amount of novelty-induced grooming of aged rats (26-28 months) was about two times that of young animals (6-8 months). This increase in novelty-induced grooming of aged animals was attributable to an increase in the number of grooming bouts, prolongation of each grooming bout, and a slight increase in the duration of licking elements. However, there were no age differences in the percentage of face washing and the duration of face-washing elements. These results are discussed in terms of behavioral aging and age-related changes in peptidergic pathways in the brain.

Contribution of self-grooming to onset of puberty in male rats

Self-grooming was observed to increase during the prepubertal period of Long-Evans rats. Males were significantly more likely than females to engage in genital grooming during this period. To determine whether self-grooming contributes to the onset of puberty, males were fitted with collars that either prevented or allowed self-grooming of hindquarters or were left uncollared from 27 to 48 or 55 days of age when autopsied to determine weight of accessory organs. Ventral, dorsal, and lateral prostates and seminal vesicles were significantly lighter in those rats wearing collars that prevented self-grooming. It was concluded that self-grooming, probably of the genitals, contributes to accessory organ growth in males of this species.

Hippocampal damage: effects on dopaminergic systems of the basal ganglia

Although the research topics discussed in this chapter cover a substantial range of areas, methods, and behaviors, there is a consistent central issue: the alterations of brain and behavior subsequent to hippocampal lesions. The initial hypothesis that important secondary changes occur in the basal ganglia after hippocampal lesions has been sustained, at least in part, but other and unexpected results have been obtained that both clarify and mystify at the same time. The restoration of normal locomotion to animals with hippocampal damage by the application of a DAi agonist, DPI, to n. accumbens certainly supports our general idea, but the fact that membrane and transmitter changes in accumbens are transitory needs to be explained and perhaps related to alterations in DA receptor populations. The fact that intra-accumbens DPI can restore ACTH-induced excessive grooming at 28 days after hippocampal damage supports the idea that progressive changes are occurring in DA receptors in n. accumbens, but we need to know their nature more precisely. To do this, however, will probably require advances in our general knowledge of central DA receptors. One of the more interesting aspects of our observations is that the intra-accumbens administration of DPI restores normal behavioral patterns in several types of behaviors, especially locomotion and the excessive grooming response. These two behaviors are not closely linked in nature because large changes can occur in them independently, given appropriate conditions for testing. On the basis of available evidence both of these behaviors seem linked to activities in forebrain DA systems. This would further support the idea that the hippocampus modulates DA activities in basal ganglia systems. The results that suggest the presence of multiple sites for the central induction of grooming were also unexpected. As evidence mounts in support of this idea, it is likely that the one located in n. accumbens is more influenced by hippocampal destruction than the region(s) affected by icv neuropeptide administration. The interactions that take place in the basal ganglia can be extensive. Afferents from the entirety of the neocortical surface, the limbic system, and the projections from the brainstem DA cell groups meet in the striatum and ventral striatum. The efferents from this region not only reach motor cortical and subcortical sites but also project back onto diffusely projecting monoaminergic cells of the brainstem.(ABSTRACT TRUNCATED AT 400 WORDS)

The time course of excessive grooming after neuropeptide administration

In this paper we review the temporal pattern of excessive grooming in the hour or so following the central injection of ACTH1-24 in the rat. Changes in the grooming pattern after specific neuropharmacological manipulations of dopaminergic and opiate-related systems are presented which indicate a differential sensitivity of the grooming responses at different times after injection. The grooming affected by dopaminergic antagonists and opiate agonists and antagonists occurs in the last 30 min of the observation period while that found earlier is unaffected. It is also the grooming in this last 30 min of the observation period term tolerance to central administration of ACTH1-24. In contrast lesions of the central nervous system that affect excessive grooming, i.e., the substantia nigra and the hippocampus, reduce grooming throughout the observation period. The present analysis has provided evidence for dopamine/opiate insensitive and sensitive systems in excessive grooming, and thus temporal aspects are of extreme importance to the understanding of central neuropeptide influences on behavior.

ACTH-(1-24) and RX 336-M induce excessive grooming in rats through different mechanisms

ACTH-(1-24) (0.03-6 micrograms i.c.v.) and RX 336-M (7,8-dihydro-5',6'-dimethylcyclohex-5'-eno-1',2',8',14 codeinone) (1.5-6 mg/kg i.p.) induce dose-related excessive grooming and 'wet-dog' shaking in rats. In the present study, the grooming associated with these compounds was compared and analyzed pharmacologically. Grooming caused by RX 336-M and by ACTH-(1-24) was antagonized when rats were pretreated with comparable doses of morphine (0.5-4 mg/kg s.c.), however, only ACTH-(1-24)-induced grooming was attenuated by naloxone (1 and 10 mg/kg s.c.). ICI 154,129 (N,N-bisallyl-Tyr-Gly-Gly-psi-(CH2S)-Phe-Leu-OH) (30 mg/kg s.c.), a selective delta-opiate receptor antagonist, was ineffective against both ACTH-(1-24) and RX 336-M. Although haloperidol is known to antagonize grooming elicited by ACTH-(1-24) (e.g., Wiegant et al., 1977, European J. Pharmacol. 41, 343), even a high dose of this neuroleptic agent (5 mg/kg s.c.) only partially attenuated grooming caused by RX 336-M. Tolerance developed to the grooming elicited by RX 336-M, and by ACTH-(1-24), but there was no cross-tolerance. Both agents were active in genetically hypotrichotic rats; and, again in such animals, even after numbing the area caudal to the shoulders with lidocaine. Given the divergent results with naloxone, and, possibly, with haloperidol, and the lack of cross-tolerance, we conclude that the excessive grooming induced in rats by ACTH-(1-24) and by RX 336-M is mediated by different mechanisms.

A study of the shaking and grooming induced by RX 336-M in rats

Several endogenous peptides and experimental agents induce "wet-dog" shakes and excessive grooming after acute administration to rats, but quantitative information on a possible relationship between the two behaviors is lacking. RX 336-M (7,8-dihydro-5'-6'-dimethylcyclohex-5'-eno-1',8',14 codeinone) is a novel compound which elicits dose-related shaking and grooming in the rat. We have measured and compared the shaking and grooming induced by several doses of RX 336-M (1.5-12 mg/kg, IP) in male Sprague Dawley rats at various stages of maturation. Analysis of the correlation between the number of "wet-dog" shakes and the frequency of grooming episodes indicates that a relationship may exist between the shaking and grooming. The excessive grooming induced by RX 336-M may be a mechanism by which the rat's state of arousal (raised by the shaking) is lowered and homeostasis is maintained.

Central nervous system and peripheral effects of ACTH, MSH, and related neuropeptides

Adrenocorticotropic Hormone (ACTH), Melanocyte-Stimulating Hormone (MSH), and related peptides have been shown to have several neurogenic effects: alteration of cerebral protein synthesis, RNA synthesis, protein phosphorylation, and neurotransmitter turnover. Furthermore, there appears to be an ACTH containing circuit in the CNS which originates in the arcuate nucleus. Changes in concentration of the peptides in this family have been shown to alter electrophysiology, neuromuscular function, and behavior (e.g., grooming, learning) in infrahuman subjects. These findings suggest that the neuropeptides MSH and ACTH influence the capacity of an organism to efficiently evaluate information and influence the affective functioning of humans.

Short-term modulation of domestic pigeon (Columbia livia L.) behaviour induced by intraventricular administration of ACTH

The behavioural responses induced in adult domestic pigeons by intraventricular injections of 0 to 6 IU of ACTH 1-39 are reported. The frequency of 10 different behaviour patterns was recorded for 90 min after administration of the peptide. The effect that was induced was complex, the frequency of some patterns increasing (yawning, headshaking, body shaking, wing-flapping), or some others decreasing (feeding, one-wing stretching, eye closing) or remaining unchanged (preening). The frequency of several patterns was maximal during the first 30 min following the injections but this was shown in some cases to be independent on the hormone administration.

Intraventricular ACTH reduces social interaction in male rats

Intraventricular ACTH (1.25 microgram), ACTH (1.6 microgram) and ACTH:D-Phe (1.6 microgram) resulted in significant reductions in the time that pairs of male rats spent in active social interaction. This decrease in social behaviour was not accompanied by a decrease in motor activity. The results are similar to those previously found with peripheral administration of ACTH and suggest that these behavioural effects of ACTH are centrally mediated. None of the ACTH fragments had a significant effect on the latency with which thirsty rats started drinking in an unfamiliar environment. The results are discussed in relation to a possible anxiogenic action of ACTH.