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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acute exposure to toluene and other volatile organic solvents results in neurotoxicity characterized by nervous system depression, cognitive and motor impairment, and alterations in visual function. In vitro, toluene disrupts the function of N-methyl-D-aspartate (NMDA)-glutamate receptors, indicating that effects on NMDA receptor function may contribute to toluene neurotoxicity. NMDA-glutamate receptors are widely present in the visual system and contribute to pattern-elicited visual-evoked potentials (VEPs) in rodents, a measure that is altered by toluene exposure. The present study tested the hypothesis that effects on NMDA receptors contribute to toluene-induced alterations in pattern-elicited VEPs. Prior to examining the effects of NMDA receptor agonists and antagonists on toluene-exposed animals, a dose-range study was conducted to determine the optimal dose for NMDA (agonist) and MK801 (antagonist). Dose levels of 2.5 mg/kg NMDA and 0.1 mg/kg MK801 were selected from these initial studies. In the second study, Long-Evans rats were exposed to toluene by inhalation, and VEPs were measured during toluene exposure in the presence or absence of NMDA or MK801. Pattern-elicited VEPs were collected by exposing rats to a sinusoidal pattern modulated at a temporal frequency of 4.55 Hz. Following collection of baseline VEPs, rats were injected with either saline, NMDA (2.5 mg/kg, ip), or MK801 (0.1 mg/kg, ip) and 10 min later were exposed to air or toluene (2000 ppm). VEP amplitudes were calculated for 1x (F1) and 2x stimulus frequency (F2). The F2 amplitude was reduced by approximately 60, 60, and 50% in the toluene-exposed groups (TOL): SALINE/TOL (n = 11), NMDA/TOL (2.5 mg/kg; n = 13), and NMDA/TOL (10 mg/kg, n = 11), respectively. Thus, NMDA (2.5 and 10 mg/kg) did not significantly affect toluene-mediated F2 amplitude effects. Administration of 0.1 mg/kg MK801 prior to toluene exposure blocked the F2 amplitude decreases caused by toluene (n = 9). However, when 0.1 mg/kg MK801 was administered 20 min after the onset of toluene exposure, toluene-mediated F2 amplitude decreases persisted despite the challenge by MK801. These data support the hypothesis that acute actions of toluene on pattern-elicited VEPs involve NMDA receptors.
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PMID:Evaluating the NMDA-glutamate receptor as a site of action for toluene, in vivo. 1742 Feb 19

Gene expression profiles in the periaqueductal gray (PAG) of adult Long-Evans rats as a function of a stressful social defeat in inter-male fighting encounters were examined. This social subordination model mimics prototypical behavioral changes that parallel aspects of clinical depression, has been postulated to simulate early changes in the onset of depression in the losers, and has been successfully utilized for the evaluation of antidepressant activity. The 22-kHz ultrasonic vocalizations (USVs) have been shown to reflect negative emotional states akin to anxiety and depression. Social defeat is the most robust and reliable method of eliciting these calls. The PAG has been shown to be a key brain region for the generation of 22-kHz ultrasonic vocalizations, and 22-kHz USVs have been shown to be controlled by the mesolimbic cholinergic system. In this present study, we examined gene expression changes in the PAG of social subordinate rats compared to dominant rats that do not Exhibit 22-kHz USVs. We found that social defeat significantly altered the genes associated with cholinergic synaptic transmission in the PAG. The most robust of these were the increased expression of the beta2 subunit of the nicotinic acetylcholine receptor (CHRNB2) and the T subunit of acetylcholinesterase (ACHE) in the subordinate animals. These changes were corroborated by quantitative real-time polymerase chain reaction (qRT-PCR) and found to be exclusive to the PAG compared to seven other brain regions examined. These data suggest that cholinergic transmission in the PAG is involved in the generation of 22-kHz USVs and provide potential therapeutic targets for the treatment of affective disorders.
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PMID:Social defeat, a paradigm of depression in rats that elicits 22-kHz vocalizations, preferentially activates the cholinergic signaling pathway in the periaqueductal gray. 1745 55

Do light intensity and behavioral state regulate synaptic plasticity in the visual cortex? We have shown previously that synaptic transmission in the visual cortex oscillates between elevated and depressed levels in accordance with the diurnal light-dark cycle. In this study, we examined the role of intrinsic, light-independent, and visual activity-driven sensory information on the field response during diurnal fluctuations, and examined the plasticity properties of the visual cortex under both conditions. Recordings were obtained from layer 2/3 of the primary visual cortex, of adult freely moving Long Evans rats, after stimulation of the dorsal lateral geniculate nucleus. We observed that visual experience during different states of vigilance leads to increased responsiveness, and plastic changes, in the strength of connections among neurons, consistent with a naturalistic shift in the induction thresholds for synaptic plasticity. We identified this phenomenon as BDNF-dependent. We also found that gamma oscillatory activity, which increases during active visual exploration, is tightly associated with suppression of cortical field potentials, suggesting that coincident changes in synaptic responsiveness and gamma oscillatory levels may reflect mechanisms for optimal stimulus-feature encoding. Translating into an increased signal-to-noise ratio, field depression could thus alter the efficacy of cortical visual processing. These data indicate that the adult visual cortex serves as a synaptic network, where the ability to process visual stimuli is dynamically modified by active visual exploration and arousal states.
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PMID:Intrinsic, light-independent and visual activity-dependent mechanisms cooperate in the shaping of the field response in rat visual cortex. 1767 Sep 89

Using Long-Evans rats tested in a water maze, this study assessed the role of 5-HT1A/5-HT7 receptors of the medial septum in encoding, consolidation, and retrieval of spatial information. The testing protocol (acquisition: daily four-trial sessions over three consecutive days; retention: probe trial on day 4) was first validated by showing that intraseptal infusions of lidocaine (LIDO; 40 microg/0.5 microL) disrupted acquisition and retrieval of the task. 8-OH-DPAT (4 microg/0.5 microL) infused before each acquisition session prevented learning/retention of the platform location, an effect attenuated by pretreatment with the 5-HT1A receptor antagonist WAY 100635. With the 5-HT7 antagonist SB 269970, the 8-OH-DPAT-induced acquisition deficit seemed attenuated, but there was no subsequent retention. When infused immediately, 1, 4, or 6 h after each acquisition session, 8-OH-DPAT did not hinder consolidation. When the infusions were performed 2 h postacquisition, however, consolidation was disrupted. Finally, when infused before a probe trial after drug-free acquisition, 8-OH-DPAT had no effect, suggesting no interference with retrieval processes. We also established that 8-OH-DPAT had no effects when the platform was visible, and altered neither home-cage activity nor anxiety-related behavior (elevated plus-maze). Altogether, these results show that 5-HT1A receptors in the septal region contribute both to declarative-like information encoding and subsequently, within a given postacquisition time window, to its consolidation. They do not participate in the retrieval of recently learned declarative-like information. These observations suggest that 5-HT1A receptors of the medial septum contribute to a serotonin-mediated mechanism involved in the encoding and consolidation, not the retrieval of spatial hippocampal-dependent knowledge. These results might have some relevance to approaches aimed at modifying serotonergic functions in the brain for the treatment of disorders such as depression, anxiety, post-traumatic stress, and amnesia.
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PMID:Activation of septal 5-HT1A receptors alters spatial memory encoding, interferes with consolidation, but does not affect retrieval in rats subjected to a water-maze task. 1792 24

The effects of N-methyl carbamate pesticides on the photic after discharge (PhAD) of flash evoked potentials (FEPs) and the relationship between inhibition of brain cholinesterase (ChE) activity and the PhAD were evaluated. FEPs were recorded in Long Evans rats treated with physostigmine (s.c.) 0, 0.05, 0.1, 0.2 or 0.3mg/kg (free base), in an ascorbic acid/saline vehicle, carbaryl (p.o.) 0, 1, 3, 10, 30, 50 or 75 mg/kg, or propoxur (p.o.) 0, 0.3, 3, 10, 20, 30, or 40 mg/kg in a corn oil vehicle. Physostigmine served as positive control based on literature data. Early (e.g. peak N(36)) and late FEP components (peak N(166) and PhAD) are related to the initial retino-geniculate afferent volley and higher cortical processing of visual information, respectively. Compared to controls, the PhAD duration decreased following treatment with 0.1 and 0.3mg/kg physostigmine, 7 5 mg/kg carbaryl or 30 mg/kg propoxur. Lesser changes were noted in FEP amplitudes or peak latencies. Treatment with 0.2 or 0.3 mg/kg physostigmine increased peak N(36) latency. Peak N(166) latency increased only following exposure to 40 mg/kg propoxur. None of the compounds altered peak N(36) or N(166) amplitudes. Hypothermia was observed at doses greater than 0.05 mg/kg physostigmine, at 30 or 50 mg/kg carbaryl, and after treatment with 10, 20 or 40 mg/kg propoxur. Inhibition of brain ChE activity occurred at dosages greater than 0.05 mg/kg physostigmine, 1mg/kg carbaryl, and 0.3 mg/kg propoxur. Linear regression analysis indicated that the decrease in PhAD duration correlated with decrease in brain ChE activity. The results indicate that at 30 min after treatment, inhibition of brain ChE activity did not affect cortical processing of the input from the retino-geniculate volley (evidenced by unaltered peak N(36) amplitude). However, the data suggest that disruption of cortical processing of visual signals related to FEP late components, as indicated by depression of the PhAD, was related to inhibition of brain ChE activity.
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PMID:Depression of the photic after discharge of flash evoked potentials by physostigmine, carbaryl and propoxur, and the relationship to inhibition of brain cholinesterase. 1795 Aug 90

Anxious and dysthymic personality traits were measured in a euthymic, familial sample of bipolar (BPD) individuals and their affectively ill and unaffected relatives. According to the quantitative genetic model of bipolar spectrum illness [Evans, L., Akiskal, H.S., Keck, Jr., P.E., McElroy, S.L., Sadovnick, A.D., Remick, R.A., Kelsoe, J.R., 2005. Familiality of temperament in bipolar disorder: support for a genetic spectrum. J. Affect. Disord. 85, 153-168], these traits should be normally distributed with the bipolar disorder I (BPD I) group showing the highest and the unaffected relatives the least "pathological" scores. Three hundred individuals from 47 bipolar disorder families were administered a battery of personality questionnaires (Temperament Evaluation of Memphis, Pisa, Paris, and San Diego; Temperament and Character Inventory; Affective Neuroscience Personality Scale) as well as a self-rating depression (Beck Depression Inventory) and mania (Altman Self-Rating Mania) scale. Out of the 300 participants, 58 were diagnosed with BPD I, 27 with bipolar disorder II (BPD II), 58 with recurrent major depression (MDE-R), 45 had one previous depressive episode (MDE-S), and 88 were unaffected. The BPD I group scored significantly higher than their unaffected relatives on the Harm Avoidance and Sadness scales of the TCI and ANPS, respectively, while the MDE-R but not the BPD samples scored significantly higher than unaffected relatives on the Anxious Temperament (AT) subscale of the TEMPS-A. In general, the mean dysthymic personality scores were highest in the BPD sample, followed by the MDE-R, MDE-S, and unaffected relative groups. Nevertheless, no significant personality differences were found between the psychiatrically-ill groups. While dysthymic temperament traits conform relatively well to the quantitative genetic model of affective illness, anxious traits as defined by the AT scale, are equally salient in BPD and unipolar depression.
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PMID:Dysthymic and anxiety-related personality traits in bipolar spectrum illness. 1819 25

Anxiety and depression commonly occur in the pathology of rheumatic diseases. Little is known about how inflammatory disease in its early stage, before any clinical manifestation, may affect general activity. The aim of this study was to compare the anxiety-like behaviour in the early stage of adjuvant arthritis (AA), and the paw edema, and corticosterone (CORT) levels in the developed stage of AA among male and female Long Evans rats. The behavioural activity was evaluated by elevated plus maze tests. These revealed significantly reduced number of entries into the open arm of the maze in arthritic males compared to controls or to females 4 days after AA induction. Arthrihtic and control females did not differ. The number of entries into the closed arm of the maze was the same across the genders and studied intervals. Time spent in the open arm was significantly lower in arthritic males against controls or arthitic females. Time spent in the closed arm showed inverse picture to the time spent in the open arm. Hind paw swelling measured on day 23 of AA was the same in males and females, as was the elevation of CORT levels in plasma. Male rats showed anxiety-like behaviour on day 4 of AA, while female rats did not show any change, indicating different brain sensitivity to early inflammation among the genders.
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PMID:Early stage of adjuvant arthritis alters behavioral responses in male but not female rats. 1827 2

Norepinephrine is known to play an integral role in different aspects of behaviour, such as attention and arousal. It has also been implicated in the neurobiology of attention-deficit/hyperactivity disorder (ADHD). The present study was undertaken to determine the differential effects of glutamate on norepinephrine release in hippocampal slices of several rat strains. Two of the strains used in this study model behavioural disorders i.e. spontaneously hypertensive rats (SHR) mimic the behavioural characteristics of ADHD and Wistar-Kyoto (WKY) rats have been used to model depression/anxiety-like behaviours. To achieve the aims of this study, an in vitro superfusion technique was used to determine glutamate-stimulated release of radioactively labelled norepinephrine in hippocampal slices. The results show (1) SHR and Wistar rats released significantly more [(3)H]norepinephrine in response to a 1-min pulse of glutamate (1 mM) than WKY, Sprague-Dawley and Long-Evans rats. (2) Glutamate-stimulated release of [(3)H]norepinephrine was reduced by the AMPA receptor antagonist, CNQX (1 muM), suggesting that AMPA receptors are involved. (3) Exposure of hippocampal slices to a second and third 1-min pulse of glutamate revealed significant decreases in the peaks of [(3)H]norepinephrine release suggesting internalization of AMPA receptors. The rate of AMPA receptor internalization was slower in SHR than in WKY. (4) The NMDA receptor antagonist, MK-801 (10 microM) increased glutamate-stimulated release of [(3)H]norepinephrine in SHR hippocampus. This effect was blocked by CNQX, suggesting that AMPA receptors were required for the NMDA effect and that there was an NMDA component of AMPA receptor internalization in SHR hippocampus which was not evident in WKY. The present findings reveal a novel NMDA component that influences AMPA receptor-mediated regulation of norepinephrine release in SHR hippocampus.
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PMID:Glutamate-stimulated release of norepinephrine in hippocampal slices of animal models of attention-deficit/hyperactivity disorder (spontaneously hypertensive rat) and depression/anxiety-like behaviours (Wistar-Kyoto rat). 1829 91

Repeated application of low-frequency stimulation can interrupt the development and progression of seizures. Low-frequency stimulation applied to the corpus callosum can also induce long-term depression in the neocortex of awake freely moving rats as well as reduce the size of neocortical movement representations (motor maps). We have previously shown that seizures induced through electrical stimulation of the corpus callosum, amygdala or hippocampus can expand the topographical expression of neocortical motor maps. The purpose of the present study was to determine if low-frequency stimulation administered to the corpus callosum could reverse the expansion of neocortical motor maps induced by seizures propagating from the hippocampus. Adult Long-Evans hooded rats were electrically stimulated in the right ventral hippocampus, twice daily until 30 neocortical seizures were recorded. Subsequently, low-frequency stimulation was administered to the corpus callosum once daily for 20 sessions. High-resolution intracortical microstimulation was then utilized to derive forelimb-movement representations in the left (un-implanted) sensorimotor neocortex. Our results show that hippocampal seizures result in expanded motor maps and that subsequent low-frequency application can reduce the size of the expanded motor maps. Low-frequency stimulation may be an effective treatment for reversing seizure-induced reorganization of brain function.
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PMID:Low-frequency stimulation reverses kindling-induced neocortical motor map expansion. 1835 27

In this study, we compared the depression-like symptoms induced by olfactory bulbectomy (OBX) in the two inbred Wistar and Long Evans rat strains. We also analyzed the self-regulated oral intake of nicotine in these strains and the effect of nicotine on the depression-like symptoms of olfactory bulbectomy. Furthermore, we compared the antidepressant-like effects of nicotine on Wistar rats to those of transcranial magnetic stimulation (TMS), which has emerged as a therapeutic alternative for depression management. Our results show that Wistar rats develop depression-like symptoms, demonstrated by the forced swim test (FST), 4 weeks after OBX. However, in bulbectomized Long Evans rats these symptoms cannot be assessed due to a higher degree of variability of the swimming behavior of this strain. These results suggest that there are some innate differences in susceptibility to stress between these two rat strains. In Wistar rats, voluntary oral nicotine intake (1.2 mg/(kg day) for 14 days) as well as nicotine administered as a single daily i.p. injection (1.5 mg/(kg day) for 14 days) decrease the depression-like symptoms of OBX. Daily transcranial magnetic stimulation (60 Hz and 0.7 mT for 2h/day for 14 days) also decreases depression-like symptoms but is less effective than nicotine. In conclusion, our results support the idea that there are possible innate differences for depression susceptibility and that nicotine and TMS may be useful in the treatment of this syndrome.
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PMID:Antidepressant-like effects of nicotine and transcranial magnetic stimulation in the olfactory bulbectomy rat model of depression. 1858 40


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