Modelling the anxiety-depression continuum in chicks.

The clinical syndromes of anxiety and depression are now thought to exist along a temporal continuum and this construct has been modelled in a preclinical setting in chicks separated from conspecifics. This research sought to further the validity of the chick anxiety-depression continuum model. Dose-response studies using two classes of anxiolytics (chlordiazepoxide: 2.5, 5.0, 10.0, 15.0 mg/kg, and clonidine: 0.1, 0.15, 0.2, 0.25 mg/kg) and three classes of antidepressants (imipramine: 1.0, 3.0, 10.0, 15.0 mg/kg, maprotoline: 2.5, 5.0, 10.0, 20.0 mg/kg and fluoxetine: 1.0, 5.0, 10.0, 20.0 mg/kg) showed an ability to detect anxiolytic activity of chlordiazepoxide, clonidine, imipramine and maprotoline in the anxiety-like phase of the model and to detect antidepressant effects of imipramine, maprotoline and fluoxetine in the depression-like phase of the model. In addition, blood plasma interleukin-6, a biomarker of stress, was found to be elevated in response to social-separation stress. Collectively, these findings further characterize the model as a simulation of the anxiety-depression continuum and begin to establish the paradigm as a high-utility adjuvant to rodent screening assays for putative anxiolytic and antidepressant compounds.

Anti-inflammatory and anti-hyperalgesic effects of sesquiterpene lactones from Magnolia and Bear's foot.

Sesquiterpene lactones possess a variety of biological activities, including anti-inflammatory activity. Two plants native to the southeastern United States, Magnolia grandiflora (L.) and Smallanthus uvedalius (L.) [syn Polymnia uvedalius (L.)], are novel sources of the sesquiterpene lactones parthenolide and enhydrin, respectively. In this study, the anti-inflammatory and anti-hyperalgesic effects of these isolated lactones from these two plant sources were evaluated in the rat carrageenan inflammation model. Rats received ip injections of either vehicle (propylene glycol), indomethacin (5 mg/kg), 11,13-dihydroparthenolide (20 mg/kg), parthenolide (5 or 20 mg/kg) or enhydrin (5 or 20 mg/kg). A 100-microl injection of 2.0% carrageenan was made into the plantar surface of the right hindpaw. Paw withdrawal latencies and paw volumes in both inflamed and non-inflamed paws were recorded at four test intervals: pre-inflammation baseline (0 time point), and 1, 2 and 4 h post-carrageenan injection. Vehicle-treated animals exhibited a significant time-dependent hyperalgesic and edema response that was greatest at the 4-h test interval. Indomethacin significantly blocked the hyperalgesic response and modestly attenuated the edema response. Parthenolide (20 mg/kg) and enhydrin (20 mg/kg) significantly blocked the hyperalgesic response and significantly attenuated the edema response; 11,13-dihydroparthenolide did not affect either inflammation or hyperalgesia. These findings suggest that parthenolide and enhydrin from these plant sources may be useful in the treatment of inflammatory pain.

Anxiolytic effects of kava extract and kavalactones in the chick social separation-stress paradigm.

RATIONALE: Piper methysticum extract (kava kava) possesses numerous therapeutic properties, but it is unknown which of its principle constituents (kavalactones) subserve such effects. OBJECTIVES: This experiment sought to characterize the putative anxiolytic properties of P. methysticum extract and its six principle kavalactones in the chick social separation-stress paradigm. METHODS: Eight-day-old chicks received intraperitoneal injections of either vehicle, chlordiazepoxide (5.0 mg/ml per kg), P. methysticum extract (containing 30% kavalactones), kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, or desmethoxyyangonin (30 mg/ml per kg for kava compounds) 30 min prior to being tested in the presence of two conspecifics or in isolation for a 3-min observation period. Latency to adopt a ventral recumbent posture to index sedation, number of vocalizations to index separation distress, and a composite pain score (in response to 50 microliters 0.10% formalin injection into the plantar surface of the foot) to index stress-induced analgesia served as dependent measures. RESULTS: Both chlordiazepoxide and P. methysticum extract attenuated separation-induced distress vocalizations and stress-induced analgesia. Dihydrokavain attenuated separation-induced distress vocalizations. CONCLUSIONS: These findings suggest that the anxiolytic effects of P. methysticum extract may be mediated, in part, by dihydrokavain.

Anxiolytic properties of botanical extracts in the chick social separation-stress procedure.

RATIONALE: The recent growth in sales of natural products labeled as dietary supplements in the United States has renewed scientific interest in the study of the therapeutic effects of multi-component botanical products. OBJECTIVES: This study sought to determine whether botanical extracts derived from the Rutaceae family, Acori graminei, the Magnoliaceae family, Alchemilla vulgaris and Primula veris, which had previously been identified in bioassays as having potential anxiolytic activity, were active in the chick social separation-stress procedure. METHODS: Eight-day-old chicks received IP injections of test articles 30 min before being tested in the presence of two social companions or in isolation for a 3-min observation period. Dependent measures were: a) latency to adopt a ventral recumbent posture to index sedation, b) number of vocalizations to index separation-distress and c) a composite pain score (comprised of footlift frequency and footlift duration in response to 50 microl of 0.10% formalin injected into the plantar surface of the foot) to index stress-induced analgesia. RESULTS: Proprietal extracts NPS00033 from the Rutaceae plant family and NPS00039 (Relora) from the Magnoliaceae plant family screened positive in this chick model without causing sedation. CONCLUSIONS: These results suggest that botanical extracts Relora and NPS00033 may be useful in modulating anxiety states.

Benzodiazepine receptor function in the chick social separation-stress procedure.

The role of benzodiazepine (BZ) receptors in modulating social separation-induced distress vocalizations (DVocs) and stress-induced analgesia (SIA) were examined in 8-day-old cockerels (Gallus gallus). In Experiment 1, the BZ agonist chlordiazepoxide (CDP; 5.0 mg/kg) reversed both DVocs and SIA in isolated chicks. Coadministration of the BZ antagonist flumazenil (0.01, 0.03, or 0.10 mg/kg) reversed CDP anxiolytic effects. In Experiment 2, the BZ agonists alprazolam (ALP; 0.065, 0.125, 0.25, or 1.50 mg/kg) and lorazepam (LOR; 0.125, 0.25, 0.50, or 1.0 mg/kg) dose dependently reversed social separation-induced DVocs and SIA. The ED50s for ALP and LOR in attenuating DVocs were 0.19 and 0.34 mg/kg, respectively. These data strongly support the theory that CDP anxiolytic effects are mediated by BZ receptor activity in the chick social separation procedure (Experiment 1) and that this model is sensitive to BZ agonists of different potencies (Experiment 2).

Optimal scoring strategies and weights for the formalin test in rats.

The formalin test is a well-established model for assessing inflammatory nociceptive processes and analgesic drug effects. Previous research established the validity of an ordinal relationship among three well-defined pain behavior categories used to compute a composite pain score (CPS). However, optimal weights had not been validated. The present research used data from Coderre et al. (1993) and from Sufka and Roach (1996) to determine and validate optimal pain behavior category weights. Based on multiple regression analyses and Pearson correlations, optimal weights of 1 and 2 are proposed for behavior categories 2 and 3, respectively; behavior category 1 is not scored. These results are consistent with the work of Abbott et al. (1995) and Coderre et al. (1993) in that the ordinal relationship among category weights is preserved, and extend previous work by establishing optimal category weights.

The effects of cocaine and nandrolone co-administration on aggression in male rats.

1. Cocaine and anabolic-androgenic steroids are among the more commonly abused substances in selected populations. These agents, when used alone or in combination, have been reported to cause aggressive tendencies in both laboratory-based animal models and in human clinical situations. This project, using a resident-intruder paradigm, examined the effects of co-administration of cocaine and a typical anabolic-androgenic steroid, nandrolone decanoate, on the development of aggression in male Sprague-Dawley rats. 2. Dose response studies demonstrated that low dose cocaine (1 mg/kg) produced more aggression in a greater percentage of animals than for either the controls or groups receiving higher doses (up to 20 mg/kg). Initially, high intermittent doses of nandrolone (20 mg twice weekly) produced more aggression; however, low daily doses of nandrolone (2 mg) produced greater levels of aggression following 4 weeks of treatment. 3. Optimal doses of cocaine and nandrolone, when administered together, resulted in aggression scores that were not significantly different from controls or either drug singly. However, a greater percentage of animals receiving both drugs exhibited aggression than did rats receiving either drug alone. 4. These results support the interpretation that the drugs interact to produce unique effects in the development of aggression. However, the complexity and extent of the interactions is great and remains to be fully elucidated.

Opiate effects on isolation stress in domestic fowl.

In an attempt to examine the role of opioid system functioning in social attachment and isolation stress in young domestic fowl, the effects of morphine (5.0 mg/kg) and naloxone (5.0 mg/kg) were evaluated on distress vocalizations, thermal nociception, thermoregulation, and respiration following 15 min of isolation in 7-day-old White-Leghorn cockerels. Morphine decreased and naloxone increased distress vocalizations in isolated chicks. Isolation produced an increase in jump response latencies (i.e., hypoalgesia) on a standard hot-plate test. In general, morphine decreased and naloxone increased mean jump latencies in both isolated and nonisolated chicks. Isolation produced an increase in core body temperature (i.e., hyperthermia); morphine decreased and naloxone increased core body temperatures independent of the isolation manipulation. Social isolation did not affect respiration. However, morphine depressed respiration in both isolated and nonisolated chicks. These results support the notion that opioid systems modulate social attachment and isolation stress.

Construct validation of behavioral indices of isolation stress and inflammatory nociception in young domestic fowl.

Isolation from conspecifics can elicit a variety of behavioral responses in young domestic fowl that include increased vocalizations (VOC), ventral recumbency posturing (VRP), hypoalgesia, and hyperthermia. During tests of acute inflammatory nociception, chicks not only display several pain-related behaviors (i.e., footpecks and lifts), but also VOC and VRP. However, systematic evaluation of whether these behaviors reflect converging indices of stress and nociception remains to be conducted. In two separate experiments, 7-day-old chicks received intraplantar formalin (0.05%) or saline (0.05 ml) and were placed in sound-attenuating chambers with or without two conspecifics for a 3 min observation period. The following measures were recorded: VOC, footlift frequency (LFT), and duration (DUR, Experiment 2 only), pecks (PKS), ventral recumbency latency (VRL), body temperature (BTMP), and body weight (WGT). Principal component analyses revealed the presence of two oblique and nonmonotonically related components, one consisting of pain-related measures (i.e., LFT, DUR, and PKS) and the other consisting of stress-related measures (VOC, VRL, and BTMP). A third component, consisting of BTMP and WGT ostensibly reflects maturational variability in thermoregulatory capability. These findings support the construct validity of these behavioral indices of isolation stress and inflammatory nociception and are consistent with the notion of stress effects on nociceptive processing.

Cerebral lateralization in homosexual males: a preliminary EEG investigation.

A preliminary investigation was conducted to determine whether hemispheric patterns of electrophysiological activation in male homosexuals differ from that of male and female heterosexuals. Electroencephalographic (EEG) activity was recorded over left and right cerebral hemispheric locations while subjects performed verbal and spatial cognitive tasks. Male homosexuals demonstrated different patterns of alpha power compared to heterosexual males and females during baseline recording. Different hemispheric patterns of alpha activity also were observed between homosexual and heterosexual males during affective judgments of both verbal and spatial stimuli, but not between homosexual males and heterosexual females. These results provide further evidence of biologically-mediated functional differences between homosexuals and heterosexuals.

Effects of calcitonin on CNS monoamines following carrageenan-induced inflammation in rats.

The present study examined the effects of systemically administered calcitonin (CT, 10 IU/0.25 ml, SC) on changes in CNS monoamines (MAs) following unilateral carrageenan (CARRA)-induced inflammation in the rat hindpaw. High-performance liquid chromatography with electrochemical detection (HPLC-EC) for MAs was performed on the whole brain and rostral spinal cord. Carrageenan-evoked inflammation significantly increased brain serotonin [5-hydroxytryptamine (5-HT)], norepinephrine (NE), and dopamine (DA) levels. CT significantly reduced these CARRA-induced elevations in brain MAs. Elevated spinal cord 5-HT and NE levels were observed in CARRA-treated animals. CT administration increased 5-HT and NE in both the CARRA-treated animals and their saline controls. Spinal cord DA levels were not affected by either CARRA or CT administration. These findings suggest the involvement of CNS monoaminergic substrates in CT-induced hypoalgesia in inflammatory nociception.

Central monoaminergic changes induced by morphine in hypoalgesic and hyperalgesic strains of domestic fowl.

The present research examined morphine dose-response effects on both the formalin test and on CNS monoamine (MA) levels and the metabolites dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) in hypoalgesic (76) and hyperalgesic (SN) strains of domestic fowl. Morphine produced a significant hypoalgesic response in the 76 strain at 15-45 mg/kg and a significant hyperalgesic response in the SN strain at 5-10 mg/kg. In subsequent experiments, analyses of whole brain (minus tectum), brainstem, and spinal cord MA, DOPAC, and 5-HIAA via high-performance liquid chromatography with electrochemical detection (HPLC-EC) were performed following morphine administration in both the 76 and SN strains. Morphine produced a significant elevation of brain dopamine (DA) and a significant elevation of brain, brainstem, and spinal cord serotonin (5-HT) in both the 76 and SN strains. Morphine elevated brain norepinephrine (NE) in the 76 strain. However, morphine failed to affect brain NE in the SN strain. This distinct morphine effect on brain NE differentiates strain-dependent hypoalgesia and hyperalgesia in domestic fowl.

Morphine hyperalgesic effects on developmental changes in thermal nociception and respiration in domestic fowl (Gallus gallus).

Domestic fowl tested at 3, 5, and 7 days posthatch jumped from a heated grid more rapidly than animals tested at 14 days posthatch. Morphine (2.5 mg/kg) decreased jump latency in 14-day-old chicks but did not significantly affect jump latency in younger chicks. Respiration was lower in 3-day-old chicks than in the older groups but morphine depressed respiration at each age. In a second experiment morphine significantly decreased jump response latency in 5-day-old chicks when thermal stimulus intensity was lowered and morphine dose increased (5 mg/kg). Posttest respiration rate was depressed by morphine. Morphine hyperalgesia and respiratory depression were reversed by naloxone (5 mg/kg). However, naloxone alone increased jump response latency. Young domestic fowl are more sensitive and/or reactive to a noxious thermal stimulus and are less sensitive to morphine than 14-day-old chicks but morphine hyperalgesia was evident in both 5- and 14-day-old chicks. These hyperalgesic chicks may be tolerant at birth to morphine hypoalgesic effects on nociception.

Time-dependent codeine hypoalgesia and hyperalgesia in domestic fowl.

Recent research demonstrated that codeine produced hypoalgesia and morphine produced hyperalgesia against a noxious thermal stimulus in young domestic fowl. The bidirectional effects of these opiate agonists on nociception are inconsistent with the notion that codeine's algesic effects result through in vivo demethylation of codeine to yield morphine. In Experiment 1, the temporal pattern (15,30,60 and 120 min) of codeine (30 mg/kg) effects on thermal nociception and respiration were examined in 15-day-old cockerels. Codeine produced a time-dependent biphasic response: hypoalgesia at 15 min and hyperalgesia at 60 and 120 min. Respiration was depressed by codeine at all test intervals. To assess for opioid specificity, Experiment 2 examined the action of naloxone (5 mg/kg) on the temporal pattern (15 and 60 min) of codeine effects (30 mg/kg) on thermal nociception and respiration. Bidirectional codeine algesic effects were observed at the 15- and 60-min test intervals. Naloxone increased the codeine jump latency scores at the 15-min interval and decreased codeine jump latency scores at the 60-min interval. These results suggest that codeine engages opposed nonopioid-mediated hypoalgesic and opioid-mediated hyperalgesic nociceptive systems in this animal model. Codeine depressed respiration at both the 15- and 60-min test intervals and this respiratory depression was reversed by naloxone. These findings support the notion that codeine respiratory effects are mediated by opioid system activity.

Receptor mediation of 5-HT-induced inflammation and nociception in rats.

In light of evidence suggesting the proinflammatory and nociceptive action of peripheral serotonin (5-HT), the present study examined dose-dependent parameters of edema and algesia produced by intraplantar injections of 5-HT and the role of heterogeneous 5-HT receptors in these 5-HT-induced responses. Intraplantar 5-HT (0.05, 0.25, 0.5, or 1.0 mumols) produced paw edema at each 5-HT concentration and produced concentration-dependent increases in the nociceptive response as indexed by lifts of, and licks to the affected paw. Intraplantar pretreatment with the 5-HT1 receptor antagonist methysergide at concentrations greater than or equal to 3 nmol attenuated the 5-HT-induced (25 mumols) inflammatory and nociceptive responses. At concentrations greater than or equal to 300 nmol, both 5-HT2 receptor antagonist ketanserin and 5-HT3 receptor antagonist odansetron pretreatment blocked 5-HT-induced inflammatory and nociceptive responses. These results more completely define peripheral 5-HT-receptor-dependent systems of 5-HT-induced inflammation and nociception in rats.

Analgesic effects of S and R isomers of the novel 5-HT3 receptor antagonists ADR-851 and ADR-882 in rats.

The present study examined analgesia produced by S and R isomers of the novel 5-HT3 receptor antagonists, ADR-851 and ADR-882 (0.1-10 mg/kg s.c.) against acute thermal, mechanical and formalin-induced inflammatory pain in rats. Neither isomer of ADR-851 or ADR-882 was analgesic in the thermal or mechanical test. Similarly, neither S or R forms of ADR-882 produced significant anti-nociception in the formalin test. In contrast, ADR-851R produced significant analgesia at 3 and 10 mg/kg doses in this test, while ADR-851S produced significant analgesia only at 1 mg/kg.

Differential effects of handling on isolation-induced vocalizations, hypoalgesia, and hyperthermia in domestic fowl.

The effects of handling and subsequent brief isolation on vocalizations, thermal nociception, and thermoregulation were examined in 7-day-old cockerels. In Experiment 1, fifteen min of isolation elicited more vocalizations in handled than nonhandled chicks. Nonhandled chicks exhibited longer response latencies than handled chicks. In general, isolated chicks exhibited longer jump response latencies (i.e., hypoalgesia) on hot-plate tests than chicks tested immediately upon removal from the brooder. Compared to handled chicks tested immediately, all other groups exhibited increased core body temperatures. Experiment 2 examined these handling and isolation effects after 15 min of isolation with or without conspecifics. Chicks isolated alone vocalized more than chicks isolated with conspecifics. As in Experiment 1, handled chicks vocalized more than nonhandled chicks. Nonhandled chicks exhibited longer response latencies than handled chicks on hot-plate tests. Isolation-induced hypoalgesia was observed only in handled chicks that were isolated without conspecifics. Core body temperatures were highest in chicks isolates without conspecifics. Additionally, chicks isolated with conspecifics exhibited higher core body temperature than chicks tested immediately. Decreased core body temperature due to handling exposure was observed only in chicks tested immediately. These results demonstrate that isolation effects on vocalizations and nociception are primarily due to social isolation and that isolation effects on thermoregulation are a result of both social and environmental factors. Moreover, the increase in isolation-induced vocalizations in handled animals does not correlate well with the decrease in isolation-induced hypoalgesia and hyperthermia displayed by handled animals.

Morphine hyperalgesic effects on the formalin test in domestic fowl (Gallus gallus).

Preliminary research demonstrated that formalin injected into the foot of leghorn cockerels elicited significantly more footlifts of longer duration than physiological saline. The formalin test was subsequently used to examine morphine effects in this species. Previous research demonstrated strain-dependent naloxone-reversible morphine hyperalgesia against thermal nociception in cockerels. In Experiment 1 herein White Leghorn cockerels were given either 0.0, 0.5, 1.5, or 2.5% formalin SC into the foot 30 min after an IM injection of either physiological saline or 2.5 mg/kg morphine sulfate. The frequency and duration of formalin-elicited footlifts increased significantly as a function of formalin concentration. Morphine significantly increased footlift frequency and duration at all but the 0.0% formalin concentration. Morphine inhibited respiration in these animals. In Experiment 2, naloxone (5.0 mg/kg) significantly reversed both the hyperalgesia and the respiratory depression induced by morphine. These results demonstrate that morphine hyperalgesia in leghorn cockerels is neither unique to hot plate test procedures nor peculiar to thermal nociception. Atypical morphine effects in this model may be specific to nociception, however, because hyperalgesia was not accompanied by atypical morphine effects on respiration.

Effects of selective opiate antagonists on morphine-induced hyperalgesia in domestic fowl.

Although morphine typically produces analgesia in a variety of species, recent research has identified a biological model in which morphine produces a naloxone-reversible, paradoxical hyperalgesic response to a noxious thermal stimulus in young domestic fowl. The present study examined opioid receptor-mediation of this atypical opiate effect. Patterns of morphine hyperalgesia (1.25 to 5.0 mg/kg IM) were examined on a standard hot-plate test following administration (10 micrograms/5 microliters ICV) of the mu antagonist beta-funaltrexamine, the delta antagonist naltrindole, or the kappa antagonist nor-binaltorphimine in 15-day-old White Leghorn cockerels. Respiration measures were also recorded because they are indicative of opiate effects. Morphine produced a dose-dependent decrease in mean jump latencies (i.e., hyperalgesic effect). Mu receptor antagonism attenuated this morphine-induced hyperalgesic effect. Kappa receptor antagonism attenuated morphine-induced hyperalgesia only at the highest morphine dose (i.e., 5.0 mg/kg) and delta receptor antagonism failed to attenuate morphine-induced hyperalgesia. These results suggest that morphine-induced hyperalgesia, like morphine-induced analgesia, is mediated primarily by mu receptor activation.

The ontogeny of thermal nociception in domestic fowl: thermal stimulus intensity and isolation effects.

Socially housed leghorn cockerels were confined to a heated grid (55, 57, or 59 degrees C, Experiment 1; 59, 61, or 63 degrees C, Experiment 2) and tested at posthatch ages of 14 days (Experiment 1) and 1, 3, 7, or 14 days (Experiment 2). In Experiment 1, chicks performed a discrete jump response only at 59 degrees C. In Experiment 2, jump latency was inversely related to temperature at each age but significantly so only at 7 and 14 days posthatch. At the highest temperature, jump latency did not differ significantly across ages. At medium and low temperatures, latency increased from 1 and 3 to 7 days posthatch (antinociceptive effect) and decreased thereafter. Chicks raised in isolation from hatch to 7 days posthatch (Experiment 3) did not display the increased jump latency (antinociceptive effect) displayed by socially raised chicks. Developmental increases in jump latency may reflect stress-induced antinociceptive concomitants of neophobia that emerge with age in this precocial species and social experience may be required for the normal development of this stress-induced antinociception.