Suppression Of Exploratory Activity Research Articles

Effect of Transauricular Electroacupuncture on Stress-Induced Changes in Cognitive Function and Erosions of the Gastric Mucosa in Rats

Transauricular electroacupuncture prevented stress-induced increase in the degree of anxiety and suppression of exploratory activity in rats. This procedure significantly accelerated decision-making process during acute stress in both control and prestressed rats. Transauricular electroacupuncture decreased the number and area of erosions by producing a pronounced antistress effect at the central and peripheral levels.

Role of experimental conditions in determining differences in exploratory behavior of prenatally stressed rats.

The effect of prenatal stress was determined on exploration in situations that induce different levels of fear. Dams (12) were stressed by noise and light thrice weekly on an unpredictable basis throughout pregnancy, and 12 controls were left undisturbed. The time spent by different groups of their adult offspring of both sexes in exploration was assessed during 4 min in a plus maze; large, well-lit open field (1), and open field (2) after prior exposure to a small, dark holebox. Prenatal stress resulted in a significant reduction in the number of arm entries in the plus maze and amount of time spent in the open arms. Locomotion and rearing were also reduced in Open Field 1 and 2, but these activities and hole poking were unchanged in the holebox. It is concluded that prenatal stress renders the animal more fearful to a novel, intimidating environment, which may be expressed as a suppression of exploratory activity.

Amphetamine derivatives induce locomotor hyperactivity by acting as indirect serotonin agonists

Derivatives of amphetamine are potent releasers of both dopamine (DA) and serotonin (5-HT), but the relative contributions of DA and 5-HT release to the behavioral effects of these drugs have not been established. Previously, S-(+)3,4-methylenedioxymethamphetamine (S-(+)MDMA) was found to produce locomotor hyperactivity in rats which was dependent on 5-HT release. The present study found that MBDB (1.25, 2.5, 5.0 or 10.0 mg/kg), the alpha-ethyl derivative of MDMA that produces little or no direct DA release, also induced locomotor hyperactivity that lasted for greater than 60 min after the 5.0 and 10.0 mg/kg doses. MBDB produced spatial patterns of locomotor hyperactivity and suppression of exploratory activity (holepokes and rearings) very similar to the behavioral syndrome produced by MDMA. MBDB-induced hyperactivity was blocked by pretreatment with the selective 5-HT uptake inhibitor fluoxetine (2.5 or 10 mg/kg), suggesting that MBDB produced behavioral effects via uptake-carrier mediated release of 5-HT. Similarly, fluoxetine pretreatment blocked the locomotor hyperactivity produced by S-(+)3,4-methylenedioxyamphetamine (3.0 mg/kg) or p-chloroamphetamine (2.5 mg/kg), supporting a serotonergic basis for the action of these drugs. Tissue levels of 5-HT and its metabolite 5-HIAA were decreased 40 min after administration of S-(+)MDMA (3.0 mg/kg) or MBDB (5.0 mg/kg), and these decreases were prevented by fluoxetine pretreatment. S-(+)MDMA also produced a fluoxetine-sensitive increase of tissue DA levels, suggesting that 5-HT release may indirectly result in increased DA release, although MBDB did not significantly increase DA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Exploration of mice in a black and white test box: Validation as a model of anxiety

The validity of a black and white test box to measure changes in mouse exploratory behaviour relevant to assessment of anxiety was investigated by variation of the illumination within the test box, the use of different strains of mice, holding conditions and drug treatments. The suppression of exploratory activity in the white section caused by bright illumination was antagonised by anxiolytic agents from the benzodiazepine series, buspirone, 5-HT 3 receptor antagonists, alcohol, nicotine, morphine and SCH23390. The anxiogenic agent FG7142 exacerbated the behavioural suppression. Black C57/BL/6, brown DBA 2 and albino BKW mice were sensitive to the effects of drug treatments, whereas albino Tuck mice were less responsive. It is concluded that the characteristic change in mouse exploratory behaviour caused by anxiolytic agents is to preferentially increase exploratory behaviour in the white aversive section of the black and white test box. It is most consistently shown by (a) an increased time spent in the white section with proportional increases in (b) rearings and (c) ambulation and (d) a delay in the initial transition from the white to the black section.

Effects on mice locomotor activity of a narcotic-like principle from Psidium guajava leaves

Studies were carried out on the suppression of both exploratory and spontaneous locomotor activities in the mouse by a non-polar fraction from a methanol extract of the dried leaves of Psidium guajava. Shortly after intraperitoneal administration of this fraction, typical narcotic-like effects were observed, including catalepsy, analgesia, Straub tail, shallow respiratory movements and exophthalmos. The dose for 90% suppression of exploratory activity was between 3.3 and 6.6 mg/kg intraperitoneally and the onset of action was 6–8 min. The duration of activity was dose-dependent and, for a dose of 13.2 mg/kg given intraperitoneally, it was found to be more than 6 h. Qualitatively similar results on exploratory activity were obtained when the extract was administered orally. Doses of 3.3–6.6 mg/kg i.p. depressed spontaneous locomotor activity and tunnel running was curtailed. Higher doses abolished the spontaneous locomotor reflex action. A flavonoid compound or compounds appear to account for the activity seen.

Interruption of projections from the medial geniculate body to an archi-neostriatal field disrupts the classical conditioning of emotional responses to acoustic stimuli

We have previously found that the coupling of changes in autonomie activity and emotional behavior to acoustic stimuli through classical fear conditioning survives bilateral ablation of auditory cortex but is disrupted by bilateral lesions of the medial geniculate nucleus or inferior colliculus in rats. Auditory fear conditioning thus appears to be mediated by the relay of acoustic input from the medial geniculate nucleus to subcortical rather than cortical targets. Since the medial geniculate nucleus projects, in addition to auditory cortex, to a striatal field, involving portions of the posterior neostriatum and underlying archistriatum (amygdala), we have sought to determine whether interruption of connections linking the medial geniculate nucleus to this subcortical field also disrupts conditioning. The conditioned emotional response model studied included the measurement of increases in mean arterial pressure and heart rate and the suppression of exploratory activity and drinking by the acoustic conditioned stimulus following delayed classical conditioning, where the footshock unconditioned stimulus appeared at the end of the conditioned stimulus. The peak increase in arterial pressure and the duration of activity and drinking suppression were greater in unoperated animals subjected to delayed conditioning than in pseudoconditioned controls, where the footshock was randomly rather than systematically related to the acoustic stimulus. Increases in heart rate, however, did not differ in conditioned and pseudoconditioned groups. While the arterial pressure and behavioral responses therefore reflect associative conditioning, the heart rate response does not. Rats were prepared with bilateral lesions of the medial geniculate nucleus, bilateral lesions of the striatal field or asymmetrical unilateral lesions destroying the medial geniculate nucleus on one side and the striatal field on the contralateral side. The latter preparation leaves one medial geniculate nucleus and one striatal field intact but disconnected and thus produces a selective auditory deafferentation of the intact striatal field. Control groups included animals with unilateral lesion of the medial geniculate nucleus, with unilateral lesion of the medial geniculate nucleus combined with lesion of the ipsilateral striatal field, unilateral lesion of the medial geniculate combined with lesion of the contralateral anterior neostriatum (a striatal area outside of the medial geniculate nucleus projection field), and the unilateral lesion of the medial geniculate nucleus combined with lesion of the contralateral ventromedial hypothalamus or subparafascicular thalamus (regions which receive projections from areas adjacent to the medial geniculate nucleus, but not from the medial geniculate nucleus itself). Bilateral lesions of the medial geniculate nucleus and bilateral lesions of the striatal field both drastically reduced the magnitude of the learned changes in arterial pressure and the duration of activity and drink suppression elicited by the conditioned stimulus. However, the nonassociative heart rate increase persisted. Asymmetric lesions involving one medial geniculate nucleus and the contralateral striatal field also disrupted the arterial pressure and behavioral, but not the heart rate, response. Lesions involving one medial geniculate nucleus and the ipsilateral striatal field did not disrupt any of the responses, nor did combined lesions involving one medial geniculate nucleus and the contralateral anterior neostriatum, ventromedial hypothalamus, or subparafascicular thalamus. Thus, bilateral destruction of either the medial geniculate nucleus or the striatal field or interruption of projections linking the medial geniculate nucleus to the striatal field disrupts associative changes in autonomie activity and behavior elicited by an acoustic conditioned stimulus. We conclude that auditory fear conditioning is mediated by efferent connections linking the medial geniculate nucleus to a striatal field, a subcortical projection field involving the posterior caudate-putamen (neostriatum) and/or amygdala (archistriatum). These connections are necessary for the establishment of associatively conditioned autonomie and somatomotor responses to an acoustic stimulus but do not appear to mediate nonassociative (pseudoconditioned) responses elicited by the same stimulus.

Behaviorally selective cardiovascular hyperreactivity in spontaneously hypertensive rats. Evidence for hypoemotionality and enhanced appetitive motivation.

Spontaneously hypertensive rats (SHRs) and Wistar Kyoto controls (WKYs) were chronically instrumented for computer-assisted recording of arterial pressure (AP) and heart rate (HR) and examined during classically conditioned emotional (fear) reactions or during the performance of a repertoire of natural behaviors, including eating, drinking, grooming, exploring, and resting. The purpose of the study was to determine whether exaggerated cardiovascular reactivity in SHRs during aversive stimulation: 1) can be coupled to stimuli that before conditioning elicited negligible changes in AP and HR; 2) is accompanied by a proportionately enhanced level of emotional arousal; and 3) is specific to aversive emotional arousal or is also present during natural behaviors. The conditioned blood pressure response (in mm Hg) was greater (p less than 0.01) in SHRs (peak response, 20 +/- 3) than in WKYs (peak response, 7 +/- 1). While the conditioned pressure response was SHRs (peak response, 17 +/- 7 bpm). Behavioral tests indicated reduced emotional reactions in SHRs: SHRs showed less (p less than 0.05) drink suppression (75 +/- 17 sec) than WKYs (111 +/- 10 sec) and SHRs showed less (p less than 0.01) suppression of exploratory activity (201 +/- 40 sec) than WKYs (499 +/- 70) in the presence of the conditioned emotional stimulus. The magnitude of blood pressure changes (in mm Hg) above resting baseline was not different in SHRs and WKYs during eating (SHR, 32 +/- 3; WKY, 28 +/- 2), grooming (SHR, 17 +/- 3; WKY, 14 +/- 2), or exploring (SHR, 17 +/- 2; WKY, 18 +/- 2), but was greater (p less than 0.01) during drinking in SHRs (48 +/- 4) than in WKYs (32 +/- 2). The amount of time (sec) spent grooming (SHR, 55 +/- 23; WKY, 38 +/- 15) and exploring (SHR, 187 +/- 33; WKY, 165 +/- 42) did not differ between the strains, but SHRs spent more time (p less than 0.01) eating (SHR, 1103 +/- 88); WKY, 800 +/- 114) and drinking (SHR, 119 +/- 18; WKY, 32 +/- 12). These findings demonstrate that: 1) exaggerated cardiovascular reactivity in SHRs is readily coupled through conditioning to otherwise benign stimuli; 2) conditioned cardiovascular hyperreactivity is accompanied by a reduced not an enhanced level of conditioned emotional arousal; 3) cardiovascular hyperreactivity is not specific to aversive arousal but is nevertheless a behaviorally-specific mode of response; and 4) SHRs and WKYs differ in the performance of natural as well as emotional behaviors.