Changes in experimental conditions alter anti-predator vigilance and sequence predictability in captive marmosets

Anti-predator vigilance and its sequence predictability in captive adult male black tufted-ear marmosets (Callithrix penicillata) was analyzed under three experimental conditions: (1) four novel (maze) environment habituation trials; (2) six taxidermized (cat) predator confrontation trials in the same maze environment; and (3) four additional maze-only trials, in the absence of the cat stimulus. Significant quantitative and qualitative differences (aerial vs. terrestrial) were observed in scan and glance behaviors within and between the three experimental conditions. Furthermore, inter-scan bout sequence significantly deviated from randomness during the initial maze habituation and predator confrontation trials, as well as during all predator removal trials. This parameter, however, followed a random pattern during the course of the remaining sessions. Therefore, vigilance in marmosets seems to be an important and highly organized component of this species' anti-predation repertoire, inasmuch as it occurs at high rates, alters according to specific environmental cues and has a subtle differential adaptive response after repeated trials.     

Effects of a Post-Shock Injection of the Kappa Opioid Receptor Antagonist Norbinaltorphimine (norBNI) on Fear and Anxiety in Rats

Exposure of rats to footshocks leads to an enduring behavioral state involving generalized fear responses and avoidance. Recent evidence suggests that the expression of negative emotional behaviors produced by a stressor is in part mediated by dynorphin and its main receptor, the kappa opioid receptor (KOR). The purpose of this study was to determine if a subcutaneous injection of the long-acting KOR antagonist norbinaltorphimine (norBNI; 15.0 and 30.0 mg/kg) given 2 days after an acute exposure of rats to footshooks (5×2 s episodes of 1.5 mA delivered over 5 min) attenuates the expression of lasting fear and anxiety. We report that exposure of rats to acute footshock produced long-lasting (>4 weeks) fear (freezing) and anxiety (avoidance of an open area in the defensive withdrawal test). The 30 mg dose of norBNI attenuated the fear expressed when shock rats were placed in the shock context at Day 9 but not Day 27 post-shock. The same dose of norBNI had no effect on the expression of generalized fear produced when shock rats were placed in a novel chamber at Days 8 and 24. In contrast, the 30 mg dose of norBNI produced consistent anxiolytic effects in shock and nonshock rats. First, the 30 mg dose was found to decrease the latency to enter the open field in the defensive withdrawal test done 30 days after the shock exposure. Second, the same high dose also had anxiolytic effects in both nonshock and shock rats as evidence by a decrease in the mean time spent in the withdrawal box. The present study shows that systemic injection of the KOR antagonist norBNI had mixed effect on fear. In contrast, norBNI had an anxiolytic effect which included the attenuation of the enhanced avoidance of a novel area produced by a prior shock experience.     

Some behavioural effects of carbamazepine - comparison with haloperidol.

The experiments presented in this paper aimed to investigate the influence of atypical antiepileptic drug carbamazepine (CBZ, CAS 298-46-4) classified also as normothymic drug on spatial memory in Morris water maze test and anxiolytic effect in two-compartment exploratory test in rats. The study also investigated the probably occurring side effects (measuring cataleptic activity and motor coordination) following single and chronic administration of CBZ compared to haloperidol (HAL, CAS 52-86-8), a conventional antipsychotic. All the tests were carried out on male Wistar rats. CBZ 30 mg/kg was administered orally 60 min before the tests and HAL 0.15 mg/kg was administered orally 60 min before the tests. In the Morris test memory improvement only after chronic administration of CBZ on the 7 and 14 day of treatment was observed, whereas after 14 days of HAL treatment spatial memory impairment was noted. In the two-compartment exploratory test 30 mg/kg of CBZ had an anxiolytic effect after 7 and 14 days of treatment, whereas HAL did not show anxiolytic effect after single and chronic treatment. CBZ did not induce catalepsy after single as well as chronic administration. HAL evoked a strong cataleptic effect both after acute and chronic treatment. CBZ had no impact on motor coordination in the chimney test and HAL disturbed motor coordination in rats after single as well as chronic administration. CBZ may be an useful normothymic drug using in bipolar affective disorder treatment with co-occurred anxiety and cognitive deficits. The lack of significant side effects of CBZ may be an alternative way of treatment in comparison with older drugs, such as lithium carbonate.     

Intact LTP and fear memory but impaired spatial memory in mice lacking Ca(v)2.3 (alpha(IE)) channel

To investigate the functional roles of the Ca(v)2.3 (alpha(1E)) channel in hippocampal CA1 pyramidal neurons, we studied in vitro synaptic properties and in vivo behaviors of the Ca(v)2.3 gene deficient mice. The Ca(v)2.3 channel mRNA was identified in the hippocampal formation of the wild-type mouse by in situ hybridization. The basic excitatory synaptic transmission and long-term potentiation by theta-burst stimulation were intact in CA1 region of Ca(v)2.3-/- mice. We performed two forms of behavioral tests to examine the hippocampus-dependent function, i.e., emotional and spatial learning tests. The Ca(v)2.3-/- mice were able to establish and maintain fear memories. Although general improvement in the performance of Morris water maze test was seen in Ca(v)2.3-/- mice, they displayed an obvious impairment in the probe test. These results suggest that the Ca(v)2.3 channel plays some role in formation of the accurate spatial memory but not of the fear memory.     

Enhanced fear expression in a psychopathological mouse model of trait anxiety: pharmacological interventions

The propensity to develop an anxiety disorder is thought to be determined by genetic and environmental factors. Here we investigated the relationship between a genetic predisposition to trait anxiety and experience-based learned fear in a psychopathological mouse model. Male CD-1 mice selectively bred for either high (HAB), or normal (NAB) anxiety-related behaviour on the elevated plus maze were subjected to classical fear conditioning. During conditioning both mouse lines showed increased fear responses as assessed by freezing behaviour. However, 24 h later, HAB mice displayed more pronounced conditioned responses to both a contextual or cued stimulus when compared with NAB mice. Interestingly, 6 h and already 1 h after fear conditioning, freezing levels were high in HAB mice but not in NAB mice. These results suggest that trait anxiety determines stronger fear memory and/or a weaker ability to inhibit fear responses in the HAB line. The enhanced fear response of HAB mice was attenuated by treatment with either the α(2,3,5)-subunit selective benzodiazepine partial agonist L-838,417, corticosterone or the selective neurokinin-1 receptor antagonist L-822,429. Overall, the HAB mouse line may represent an interesting model (i) for identifying biological factors underlying misguided conditioned fear responses and (ii) for studying novel anxiolytic pharmacotherapies for patients with fear-associated disorders, including post-traumatic stress disorder and phobias.     

Anxiety and fear behaviors in adult male and female C57BL/6 mice are modulated by maternal separation

This study investigated the effects of maternal separation in C57BL/6 male and female mice during infancy on later adult fear and anxiety behaviors. Additionally, we observed the maternal behavior of the dams to examine aspects of maternal care that may be modulated by daily bouts of separation. In males, mice that experienced maternal separation during the neonatal period displayed significantly higher levels of anxiety and fear behavior, as measured by the open field test and elevated plus maze, compared to control, standard facility reared males. In females, however, maternal separation reduced anxiety and fear behavior in the open field test, but only when the females were in the diestrous phase of their estrous cycle. The 30-min daily observation of the dams revealed that the separation did not significantly alter the frequency of the maternal care provided by the dam at the time point measured. These results indicate that the emotionality of adult male and female mice can be modulated by maternal separation. However, this effect is dependent on the sex of the offspring and the phase of the estrous cycle of the female.     

Effect of bacosides, alcoholic extract of Bacopa monniera Linn. (brahmi), on experimental amnesia in mice

To investigate the effect of bacosides (alcoholic extract of brahmi) on scopolamine (3 mg kg(-1), ip), sodium nitrite (75 mg kg(-1), ip) and BN52021 (15 mg kg(-1), ip) induced experimental amnesia in mice, using Morris water maze test, all the agents were administered 30 min before the acquisition trials on each day and repeated for 4 consecutive days, and on 5th day during the retrieval trials. Bacosides on anterograde administration (before training) in mice, significantly decreased the escape latency time (ELT) during the acquisition trials for 4 consecutive days and increased the time spent (TS) in target quadrant during the retrieval trials on 5th day, and on retrograde administration (after training) bacosides were found not to affect TS significantly. Bacosides also significantly decreased the ELT and increased the TS in mice treated anterogradely with scopolamine and sodium nitrite. Bacosides did not exhibit any significant effect on TS of mice treated retrogradely with sodium nitrite. On the other hand, bacosides significantly increased the TS of mice treated retrogradely with BN52021. On the basis of the present results it can be concluded that bacosides facilitate anterograde memory and attenuate anterograde experimental amnesia induced by scopolamine and sodium nitrite possibly by improving acetylcholine level and hypoxic conditions, respectively. Beside this bacosides also reversed BN52021 induced retrograde amnesia, probably due to increase in platelet activating factor (PAF) synthesis by enhancing cerebral glutamate level.     

Aged wild-type littermates and APPswe+PS1/ΔE9 mice present similar deficits in associative learning and spatial memory independent of amyloid load

APPswe+PS1/ΔE9 transgenic (Tg) mice with Aβ plaque formation in neocortex and hippocampus were evaluated in tests measuring exploratory activity, anxiety, and memory ability using open field test (OFT), Y-maze, contextual fear conditioning (CFC), and Morris water maze (MWM). Wild type (WT) and Tg mice over eight months old showed same locomotion activity and anxiety level in novel stimulation, open field, and Y-maze contexts. In other experiments that measured associative memory and spatial memory in Tg mice and their littermates, the subjects also presented similar deficiencies in memory acquisition. These two aged groups showed abnormal freezing level variance especially in CFC test. In comparison to that in non-transgenic 8-week-old mice group, the acquisition of spatial memory in MWM task was impaired in aged WT and bigenic Tg mice. Taken together, aged wild-type littermates and Tg mice present similar deficits in associative learning and spatial memory independent of amyloid plaques.     

Effects of ACTH(1-24) and ACTH/MSH(4-10) on isolation-induced distress vocalization in domestic chicks

The effects of centrally administered ACTH(1-24) and ACTH(4-10) on isolation-induced distress vocalizations (DVs) were assessed in the presence or absence of social cues (mirrored and plain environments). A dose-response analysis indicated that ACTH(1-24) at doses of 0.5 nM and above increased DVs relative to controls when the animals were tested in mirrored or social environments which reduce baseline levels of calling. This effect, however, was short-lived (approx. 15 min). When tested again 1 hr after injection, the treated animals did not differ from controls. ACTH/MSH(4-10) had no effect on vocalization when the animals were tested immediately after injection, but marginally increased calling when animals were tested an hour later. In addition to vocalization changes, ACTH(1-24) induced squatting when animals were isolated in the test boxes, and yawning, head shaking, wing flapping and preening when animals were reunited after testing. ACTH(1-24)-treated chicks also exhibited longer latencies to close their eyes when they were held in the cupped hands of the experimenter. Taken together, the results suggest that ACTH(1-24) induces a central state of arousal in chicks that resembles fear/anxiety.     

Mouse pancreatic polypeptide modulates food intake, while not influencing anxiety in mice

This study was designed to investigate the effects of synthetic mouse pancreatic polypeptide (mPP) on feeding and anxiety in mice. The intracerebroventricular (i.c.v.) injection of mPP (0.003-3 nmol) dose-dependently increased food intake. A significant increase was observed 20 min after i.c.v. injection and continued for 4 h. The intraperitoneal (i.p.) injection of mPP (0.03-30 nmol) dose-dependently decreased food intake. A significant decrease was observed 20 min after i.p. injection and continued for 4 h. In the elevated plus maze test, the i.c.v. injection of mPP (0.003-3 nmol) did not affect anxiety behavior. These results suggest that mPP modulates food intake and the Y4 receptor in the brain may contribute to the regulation of feeding, whereas appearing not to influence anxiety in mice.     

Different effects of subchronic doses of 17-beta estradiol in two ethologically based models of anxiety utilizing female rats

Estrogen may have differing effects on 'anxiety' responses under different conditions. The current study tested the effects of estrogen on anxiety-like behavior when administered for 6-7 days in ovariectomized (OVX) female rats. Two animal paradigms were utilized; the elevated plus maze (EPM), measuring changes in innate fear of exploration of open spaces; and the social interaction test (SIT), measuring the exploration of a novel, same gender partner. In the EPM, estradiol-treated OVX females both entered and spent more time in the open arms than control OVX females, indicating an anxiolytic-like action of estradiol. In contrast, estradiol treated OVX females interacted less with the partner animal in the SIT compared with controls suggesting anxiogenic-like effects. The possible anxiogenic effect of estradiol in the SIT is supported by two findings: (1) the effect is reversed by the anxiolytic drug alprazolam and (2) estrogen did not affect locomotion and therefore, the reduced social interaction is not due to reduced activity. Acute administration of progesterone (5 mg/kg), which has anxiolytic properties, did not reverse estradiol-induced social interaction deficits, suggesting that lack of progesterone did not account for estradiol's anxiogenic effects. These results, while seemingly contradictory when interpreted within a unified concept of anxiety, may well reflect the ethological roles of reproductive hormones and their effects on different types of exploratory anxiety.     

Effects of Estrogen on Activity and Fear-Related Behaviors in Mice

Estrogen has been shown to affect nonreproductive behaviors in humans and rodents, including anxiety, fear, and activity levels. Rat studies have shown increases and decreases in these behaviors. Inconsistencies may be due to differences in testing conditions and the extent to which each test measures anxiety, fear, or activity. Few mouse studies have been performed. The present study was conducted to address these issues by examining the effect of estradiol benzoate (EB) in ovariectomized (OVX), C57BL/6 mice on a range of behavioral paradigms measuring anxiety [open field (OF), dark-light transition (DLT), elevated plus maze (EP)], activity [running wheel (RW)], and conditioned fear learning (FCon). In OF, vehicle (Veh) animals spent more time in the center than EB-treated animals and were more active overall. In DLT, Veh animals were more active than EB-treated animals in both the dark and light compartments and made more transitions between the two. In EP, Veh animals entered a greater number of arms. During FCon, EB animals froze more than Veh to the conditioned stimulus. In contrast, in the home cage RW, EB animals were more active than Veh. Factor analysis was used to characterize intertask correlations of females' behavior and to explore the possibility that estrogen may have an impact on a general arousal factor. In sum, estrogen treatment heightened fear responses in a range of fear and anxiety-provoking situations (OF, DLT, EP, and FCon), while increasing activity in the safer RW. We suggest that EB treatment may result in a generally more aroused animal.     

Age‐related alteration of emotional regulation in the BACHD rat model of Huntington disease

Huntington's disease (HD) is a genetic neurodegenerative disorder, caused by an expanded CAG repeat in the gene encoding the huntingtin protein. At the premanifest phase, before motor symptoms occur, psychiatric and emotional disorders are observed with high prevalence in HD patients. Agitation, anxiety and irritability are often described but also depression and/or apathy, associated with a lack of emotional control. The aim of the present study was to better circumscribe and understand the emotional symptoms and assess their evolution according to the progression of the disease using a transgenic HD model, BACHD rats, at the age of 4, 12 and 18 months. To achieve this goal, we confronted animals to two types of tests: first, tests assessing anxiety like the light/dark box and the conflict test, which are situations that did not involve an obvious threat and tests assessing the reactivity to a present threat using confrontation with an unknown conspecific (social behavior test) or with an aversive stimulus (fear conditioning test). In all animals, results show an age‐dependent anxiety‐like behavior, particularly marked in situation requiring passive responses (light/dark box and fear conditioning tests). BACHD rats exhibited a more profound alteration than WT animals in these tests from an early stage of the disease whereas, in tasks requiring some kind of motivation (for food or for social contacts), only old BACHD rats showed high anxiety‐like behavior compared to WT, may be partly due to the other symptoms' occurrence at this stage: locomotor difficulties and/or apathy.     

Involvement of adenosinergic receptors in anxiety related behaviours

In the present study, the effect of adenosine (A1 and A2 receptor agonist), caffeine (A2A receptor antagonist), theophylline (A2A receptor antagonist) and their combination was studied in anxiety related behaviours using elevated zero maze and elevated plus maze paradigms and compared their various behavioural profiles. Adenosine (10, 25, 50,100 mg/kg) significantly showed anxiolytic effect at all the doses, whereas caffeine (8, 15, 30, 60 mg/kg) and theophylline (30, 60 mg/kg) showed psychostimulatory action at lower doses and anxiogenic effect at higher doses. Pretreatment with caffeine (8, 15, 30 mg/kg) and theophylline (30 mg/kg) reversed the anxiolytic effect of adenosine. The study suggested the involvement of adenosinergic receptor system in anxiety related behaviours.     

Pathways of substance P stimulation of canine tracheal ciliary beat frequency.

Substance P (SP), an inflammatory neuropeptide, may be released by intraepithelial nerves in response to an irritant or inflammatory stimulus. To investigate the neural and humoral pathways mediating the response of tracheal ciliary beat frequency (CBF) to topically applied SP, CBF was measured on the ventral midtracheal surface of anesthetized beagles by using heterodyne-mode correlation analysis laser light scattering. In the first study, aerosolized SP, delivered to the lungs of eight beagle dogs, stimulated CBF in a dose-dependent manner from a baseline of 4.9 +/- 0.4 Hz to a maximum of 14.9 +/- 1.5 Hz at dose of 10(-7) M. In the second study, the tracheal lumen was isolated from the bronchial airways by inflating the cuff of an endotracheal tube near the carina. Intravenous hexamethonium bromide (2 mg/kg), ipratropium bromide (0.5 micrograms/kg), and indomethacin (2 mg/kg) were used as blocking agents to inhibit the nicotinic, muscarinic, and cyclooxygenase pathways, respectively. Aerosolized 10(-9), 10(-8), or 10(-7) M SP was delivered sequentially to the tracheal lumen for 3 min at 30-min intervals. SP caused two distinct CBF stimulatory episodes at 4 min (mean time of the maximal response) and at 18 min (mean time of the maximal response) after onset of delivery and returned to baseline after 25 min. SP stimulated CBF from the baseline of 5.1 +/- 0.4 Hz to a maximum of 14.2 +/- 2.5 Hz during the first episode (P less than 0.01) and to 10.4 +/- 0.6 Hz during the second episode (P less than 0.01) at dose of 10(-8) M. These responses were inhibited by all the blocking agents. These data suggest that SP stimulates CBF via a cyclooxygenase-dependent parasympathetic reflex.     

Loop diuretics have anxiolytic effects in rat models of conditioned anxiety

A number of antiepileptic medications that modulate GABA(A) mediated synaptic transmission are anxiolytic. The loop diuretics furosemide (Lasix) and bumetanide (Bumex) are thought to have antiepileptic properties. These drugs also modulate GABA(A) mediated signalling through their antagonism of cation-chloride cotransporters. Given that loop diuretics may act as antiepileptic drugs that modulate GABAergic signalling, we sought to investigate whether they also mediate anxiolytic effects. Here we report the first investigation of the anxiolytic effects of these drugs in rat models of anxiety. Furosemide and bumetanide were tested in adult rats for their anxiolytic effects using four standard anxiety models: 1) contextual fear conditioning; 2) fear-potentiated startle; 3) elevated plus maze, and 4) open-field test. Furosemide and bumetanide significantly reduced conditioned anxiety in the contextual fear-conditioning and fear-potentiated startle models. At the tested doses, neither compound had significant anxiolytic effects on unconditioned anxiety in the elevated plus maze and open-field test models. These observations suggest that loop diuretics elicit significant anxiolytic effects in rat models of conditioned anxiety. Since loop diuretics are antagonists of the NKCC1 and KCC2 cotransporters, these results implicate the cation-chloride cotransport system as possible molecular mechanism involved in anxiety, and as novel pharmacological target for the development of anxiolytics. In view of these findings, and since furosemide and bumetanide are safe and well tolerated drugs, the clinical potential of loop diuretics for treating some types of anxiety disorders deserves further investigation.     

Effect of ethanolic extract of root of Pongamia pinnata (L) pierre on oxidative stress, behavioral and histopathological alterations induced by cerebral ischemia--reperfusion and long-term hypoperfusion in rats

Possible effect of an ethanolic root extract of Pongamia pinnata (L) Pierre (P. pinnata) on oxidant-antioxidant status and histopathological changes in acute ischemia-reperfusion injury in the rat forebrain have been investigated. Further, its effect was also assessed on long-term cerebral hypoperfusion-induced changes in anxiety, cognitive and histopathological parameters. Cerebral post-ischemic reperfusion is known to be associated with generation of free radicals. In the present study, bilateral common carotid artery occlusion (BCCAO) for 30 min followed by 45 min reperfusion produced increases in lipid peroxidation, superoxide dismutase (SOD) activity and a fall in the total tissue sulfhydryl (T-SH) levels. The ethanolic extract of roots of P. pinnata (50 mg kg(-1), po for 5 days) attenuated the ischemia-reperfusion-induced increase in lipid peroxidation, SOD activity and a fall in T-SH levels. The extract also ameliorated histopathological changes and inflammatory cell infiltration in the frontoparietal region of the rat brain. The extract (50 mg kg(-1), po for 15 days) was also found to alleviate the long-term hypoperfusion-induced anxiety and listlessness (open field paradigm). There was an improvement of learning and memory deficits (Morris' water maze testing). It also attenuated reactive changes in forebrain histology like gliosis, lymphocytic infiltration, astrocytosis and cellular edema. Results suggest protective role of P. pinnata in ischemia-reperfusion injury and cerebrovascular insufficiency states.     

Characterization of the effects produced by neurokinins and three agonists selective for neurokinin receptor subtypes in a spinal nociceptive reflex of the rat

In the awake restrained rat the intrathecal (i.th.) administration of 6.5 pmol-40 nmol of substance P (SP), neurokinin A (NKA) or one of two selective NK-1 receptor agonists [Pro9, Met(O2)11]SP, denoted ana1 and [beta-Ala4, Sar9, Met(O2)11]SP , denoted ana2 decreased reaction time (RT) to a noxious radiant heat stimulus in a dose-related manner. The following rank order of potency was observed in relation to this response: ana1 = ana2 greater than SP much greater than NKA. The decrement of tail-flick latency was greatest at 1 min and RT returned to the basal level within 6-11 min post-administration. However, in some rats SP produced a small increase in RT (anti-nociception) at 6-11 min post-administration. The i.th. administration of neurokinin B (NKB) or a selective NK-3 receptor agonist [beta-Asp4, MePhe7]NKB), denoted ana3 induced an antinociceptive effect which was greatest at 1 min and lasted less than 11 min after NKB or more than 30 min after ana3 administration. The magnitude of the increase in RT produced by 65 pmol-40 nmol doses of these peptides is ana3 much greater than NKB much greater than SP. The effect of NKB (8.0 nmol) was significantly blocked (P less than 0.005) by prior i.th. administration of naloxone (opioid antagonist) but not by idazoxan (alpha 2-adrenoceptor antagonist), [Thi5,8, D-Phe7]BK (kinin antagonist), or following bilateral adrenalectomy. From these results, we conclude that NKB-induced antinociception is mediated by the spinal release of an opioid and not through a BK or NA mechanism. The results also suggest that the nociceptive and antinociceptive effects of neuro-kinins are mediated by the activation of NK-1 and NK-3 receptor subtypes respectively, in the rat spinal cord.     

Anxiogenic effects of substance P and its 7-11 C terminal, but not the 1-7 N terminal, injected into the dorsal periaqueductal gray

The dorsal periaqueductal gray matter (DPAG) is one of the main output regions of the brainstem for the expression of defense reaction. Recent findings implicating neurokinins in the expression of fear or anxiety-like behaviors, have stimulated interest in the participation of these neuropeptides in the generation of aversive states in the dorsal periaqueductal gray matter. Analyses of traditional measures of the behavior of rats submitted to the elevated plus-maze test in this laboratory have shown that microinjections of substance P (SP) into the DPAG produce anxiogenic-like effects. The present study employs an ethological analysis of the behavior of animals in this test to investigate the involvement of substance P (SP) and its C- and N- fragments (7-11 and 1-7) in the expression of the different aspects of fear upon injection into the DPAG. To this end, rats were implanted with a cannula in the DPAG and injected one week later with 35 and 70 pmol of either substance P, or C- or N- SP fragments and tested immediately afterwards in the elevated plus-maze. The results show that SP and its C terminal fragment, produced increases in scanning, stretched attend posture, head dipping and flat-back approach, whereas the fragment N terminal produced only an increase in rearing. Therefore, the effects of SP and its C terminal fragment were associated to risk assessment behavior, whereas those of N terminal fragment were related to vertical exploratory activity. The results indicate that SP produces anxiogenic effects through activation of neural substrates of aversion in the DPAG and that this effect is probably related to its C terminal fragment.