Effects of antisense to the (alpha)2A-adrenoceptors administered into the region of the locus ceruleus on behaviors in plus-maze and sexual behavior tests in sham-operated and castrated male rats.
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Clinical and experimental findings have implicated brain alpha2-adrenoceptors in the regulation of many physiological functions, including sexual activity and stress-related behavior. However, which subtypes of the three alpha2-adrenoceptors that have now been cloned (alpha2A, alpha2B, and alpha2C) are involved in these controls have yet to be established. Here, we investigated the contribution of alpha2A-adrenoceptors of the locus ceruleus, the principal source of brain noradrenaline, to exploratory and sexual behaviors. Using administration of antisense oligodeoxynucleotide to inhibit the receptor expression, we found that reductions in brainstem alpha2A-adrenoceptor mRNA levels and alpha2-adrenoceptor densities induced by antisense treatment were not accompanied by any changes in the major characteristics of male sexual activity, such as mount latencies and numbers of mounts. However, in sexual behavior tests, antisense-treated male rats had decreased numbers of rearings and thus have higher percentages of behaviors positively correlated with sexual activity. Besides, antisense-treated animals had decreased anxiety in plus-maze tests. The data demonstrate that inhibition of alpha2A-adrenoceptor expression in the region of the locus ceruleus has an anxiolytic-like effect and facilitates male's attention to female in sexual behavior test. (+info)
Effect of repeated stress on novelty-induced antinociception in rats.
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There is extensive evidence that acute stress induces an analgesic response in rats. On the other hand, repeatedly stressed animals may present the opposite effect, i.e., hyperalgesia. Furthermore, exposure to novelty is known to induce antinociception. The effects of repeated restraint stress on nociception after exposure to novelty, as measured by the tail-flick latency (TFL), were studied in adult male rats. The animals were stressed by restraint 1 h daily, 5 days a week for 40 days. The control group was not submitted to restraint. Nociception was assessed with a tail-flick apparatus. After being familiarized with the TFL apparatus, each group was subdivided into two other groups, i.e., with or without novelty. Animals were subjected to the TFL measurement twice. For the animals exposed to novelty, the first TFL measurement was made immediately before, and the second 2 min after a 2-min exposure to a new environment. While the control group presented an increased TFL after exposure to a novel environment, chronically stressed animals did not show this effect. These results suggest that repeated restraint stress induces an alteration in the nociceptive response, perhaps as a result of an alteration in endogenous opioids in these animals. (+info)
Phencyclidine impairs latent learning in mice: interaction between glutamatergic systems and sigma(1) receptors.
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The effect of phencyclidine (PCP) on latent learning was investigated using a one-trial water-finding task in mice. Mice without water deprivation were given PCP or saline before a training trial, which consisted of exposure to a novel open-field environment with an alcove containing a water tube. Twenty to twenty-four hours after water deprivation, animals were placed in the same apparatus and the time required to find the water tube measured (test trial). Saline-treated trained mice showed a significantly shorter time to find the water tube during the test trial (finding latency) than naive mice that had not been trained. When PCP (1mg/kg i.p.) was administered before the training trial, the finding latency was significantly prolonged in comparison with that in the saline-treated mice, indicating that PCP induced impairment of latent learning. 1-(3,4-Dimethoxy-phenethyl)-4-(3-phenylpropyl)piperazine dihydrochloride (SA4503: 0.3 mg/kg s.c.) and (+)-pentazocine (1 mg/kg s.c.), selective sigma(1) receptor agonists, or D-cycloserine (10 and 30mg/kg, s.c.), a glycine binding site agonist, significantly counteracted the PCP-induced impairment of latent learning, whereas (+)-SKF-10,047 (0.1-3 mg/kg s.c.), a putative sigma(1) receptor agonist, did not. The ameliorating effects of SA4503 and (+)-pentazocine were antagonized by N,N-dipropyl-2-(4-methoxy-3-(2-phenylethoxy) phenyl) ethylamine (NE-100: 1 mg/kg i.p.), a selective sigma(1) receptor antagonist. SA4503 also ameliorated the impairment of latent learning induced by dizocilpine, a non-competitive N-methyl-D-aspartate receptor antagonist, the effect being antagonized by NE-100. These results suggest that PCP induces an impairment of latent learning, this effect being mediated via glutamatergic systems, and that activation of sigma(1) receptors ameliorates impairment of latent learning induced by PCP. (+info)
Television campaigns and adolescent marijuana use: tests of sensation seeking targeting.
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OBJECTIVES: This study evaluated the effectiveness of targeted televised public service announcement campaigns in reducing marijuana use among high-sensation-seeking adolescents. METHODS: The study used a controlled interrupted time-series design in 2 matched communities. Two televised antimarijuana campaigns were conducted in 1 county and 1 campaign in the comparison community. Personal interviews were conducted with 100 randomly selected teenagers monthly in each county for 32 months. RESULTS: All 3 campaigns reversed upward developmental trends in 30-day marijuana use among high-sensation seekers (P < .002). As expected, low-sensation seekers had low use levels, and no campaign effects were evident. CONCLUSIONS: Televised campaigns with high reach and frequency that use public service announcements designed for and targeted at high-sensation-seeking adolescents can significantly reduce substance use in this high-risk population. (+info)
5-HT1A receptor agonists buspirone and gepirone attenuate apomorphine-induced aggressive behaviour in adult male Wistar rats.
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We have studied the effects of acute serotonin (5-HT) 5-HT1A receptor agonist buspirone (0.5, 1.0, 2.5 and 5.0 mg/kg, s.c.), gepirone (5.0 and 10 mg/kg, s.c.), and 8-OH-DPAT (0.1, 0.25, and 0.5 mg/kg, i.p.) treatment on the apomorphine-induced aggressive behaviour in adult male Wistar rats. Buspirone in doses of 2.5 and 5.0 mg/kg completely blocked, gepirone (10 mg/kg) significantly attenuated the aggressiveness, and 8-OH-DPAT abolished aggressive behaviour only in the lowest dose used (0.1 mg/kg) which effect disappeared in higher doses. The antiaggressive effect of buspirone (2.5 mg/kg) and gepirone (10 mg/kg) was not reversed by a 5-HT1A receptor antagonist WAY 100635 (0.3 mg/kg). All 5-HT1A receptor agonists tested dose-dependently decreased the exploratory behaviour of experimentally naive rats, while buspirone (2.5 mg/kg) and gepirone (10 mg/kg) had only a weak effect on the locomotor activity and stereotyped behaviour in the apomorphine-pre-sensitised rats. In conclusion, our experiments demonstrate the 5-HTIA receptors may be involved in the mediation of the apomorphine-induced aggressive behaviour in adult male Wistar rats. However, the prominent antiaggressive effect of buspirone, and to a lesser extent--gepirone, seems to be mediated by some other mechanisms, evidently via the dopamine D2 receptors. (+info)
NMDA and AMPA antagonist infusions into the ventral striatum impair different steps of spatial information processing in a nonassociative task in mice.
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Most of the research on ventral striatal functions has been focused on their role in modulating reward and motivation. More recently, a possible role of this structure in cognitive functions has been suggested. However, very little information is available on the involvement of the nucleus accumbens in the different stages of the consolidation process. In this study, the effect of focal injections of AP-5 and DNQX, competitive antagonists at the NMDA and AMPA receptors, respectively, was examined in a nonassociative task designed to estimate the ability of mice to react to spatial changes. The task consists of placing the animals in an open field containing five objects; after three sessions of habituation, their reactivity to object displacement was examined 24 hr later. AP-5 injections administered after training impaired the ability of mice to detect the spatial novelty but did not affect response when injected 120 min after training or before testing. On the contrary, DNQX did not affect response when administered immediately or 120 min after training but did impair spatial discrimination when administered before training or testing. These data demonstrate a double dissociation between glutamate receptor subtypes, such that accumbens NMDA receptors are important for consolidation and not ongoing discrimination of spatial information, whereas AMPA receptors have an opposite role in these processes. (+info)
Interference of propylene glycol with the hole-board test.
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Experimental drugs and/or plant extracts are often dissolved in solvents, including propylene glycol. Nevertheless, there is evidence for psychoactive properties of this alcohol. In this study we found that in the hole-board test 10% propylene glycol did not modify the head-dipping behavior. However, 30% propylene glycol induced an increase in the number of head-dips (46.92 +/- 2.37 compared to 33.83 +/- 4.39, P<0.05, ANOVA/Student-Newman-Keuls), an effect comparable to that obtained with 0.5 mg/kg diazepam (from 33.83 +/- 4.39 to 54 +/- 3.8, P<0.01, ANOVA/Student-Newman-Keuls). These results demonstrate that 30% propylene glycol has significant anxiolytic effects in this model and therefore cannot be used as an innocuous solvent. (+info)
Mechanism for increased hippocampal synaptic strength following differential experience.
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Exposure to novel environments or behavioral training is associated with increased strength at hippocampal synapses. The present study employed quantal analysis techniques to examine the mechanism supporting changes in synaptic transmission that occur following differential behavioral experience. Measures of CA1 synaptic strength were obtained from hippocampal slices of rats exposed to novel environments or maintained in individual cages. The input/output (I/O) curve of extracellularly recorded population excitatory postsynaptic potentials (EPSPs) increased for animals exposed to enrichment. The amplitude of the synaptic response of the field potential was related to the fiber potential amplitude and the paired-pulse ratio, however, these measures were not altered by differential experience. Estimates of biophysical parameters of transmission were determined for intracellularly recorded unitary responses of CA1 pyramidal cells. Enrichment was associated with an increase in the mean unitary synaptic response, an increase in quantal size, and a trend for decreased input resistance and reduction in the stimulation threshold to elicit a unitary response. Paired-pulse facilitation, the percent of response failures, coefficient of variance, and estimates of quantal content were not altered by experience but correlated well with the mean unitary response amplitude. The results suggest that baseline synaptic strength is determined, to a large extent, by presynaptic release mechanisms. However, increased synaptic transmission following environmental enrichment is likely due to an increase in the number or efficacy of receptors at some synapses and the emergence of functional synaptic contacts between previously unconnected CA3 and CA1 cells. (+info)