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At least 127 records · Page 7Linked to original sources
PubMed1989

Corticotropin-releasing factor modulates defensive-withdrawal and exploratory behavior in rats.

The role of corticotropin-releasing factor (CRF), an endogenous neuropeptide, in modulating species-typical responses was examined in an unfamiliar open field containing a small chamber. Rats placed in this small chamber spent most of their time withdrawn in it. However, rats given an intracerebroventricular injection (20 micrograms) of alpha-helical CRF(9-41), a CRF receptor antagonist, emerged from the chamber and explored the unfamiliar open field. Additional studies showed that after 1 exposure to the test environment, vehicle-treated rats increased their time spent in the open field and returned intermittently to the chamber. This result suggests that reexposure reduces the threatening impact of an unfamiliar open field. Importantly, CRF (300 ng) injected centrally, but not peripherally, before reexposure to the test environment significantly reduced exploration in the open field and increased a pattern of defensive-withdrawal into the chamber. Data suggest that whether defensive-withdrawal or exploratory behavior is exhibited may depend on CRF actions in brain systems that mediate the perception of threat in the environment.

Animals↗
PubMed1998

Neuronal overexpression of heme oxygenase-1 correlates with an attenuated exploratory behavior and causes an increase in neuronal NADPH diaphorase staining.

Heme oxygenase isozymes, HO-1 (also known as hsp32) and HO-2, are the source for the formation of the putative messenger molecule carbon monoxide (CO), reactive iron, and the in vitro antioxidant bilirubin. We have developed and characterized transgenic (Tg) mice that overexpress the stress protein in neurons in various brain regions. The Tg mice were generated by the use of rat HO-1 cDNA under the control of the neuron-specific enolase promoter. Except for a tendency to have an enlarged spleen, Tg mice did not show gross anatomical changes. Increase in HO-1 mRNA, which was demonstrated by northern blot analysis and in situ hybridization, was accompanied by an increase in neuronal HO-1 protein expression, shown by immunohistochemistry and western blotting, and an increase in HO activity. Expression of the transgene correlated with an attenuation of exploratory behavior and increased circling activity and coincided with enhanced neuronal NADPH diaphorase staining. Those changes were not accompanied by an increase in DNA damage or significant change in whole-brain NO synthase activity. The HO-1 Tg mice potentially represent a good model to examine the function of CO as a neuromodulator, iron as a gene regulator, and bile pigments as in vivo antioxidants.

Animals↗
PubMed1992

The role of histamine in the anterior hypothalamus and its functional interaction with the hippocampus on exploratory behavior in adult male rats.

The possible effects of histamine (HA) locally applied into the preoptic area (POA) on hippocampus-mediated behaviors were studied in adult male rats. Animals were double-implanted unilaterally with microinjection cannulae into POA and hippocampus (HPC). In experiment 1, HA was injected into POA and pyrilamine (H1-HA antagonist) or ranitidine (H2-HA antagonist) were microinjected into the ipsilateral HPC in two different doses. In Experiment 2, HA was injected into POA and the histamine antagonists were microinjected into the contralateral HPC. Ten min later the animals were tested in an automatic monitor activity. Horizontal, ambulatory and vertical movements were measured as general motor exploratory behaviors. Contact time (in seconds) to a circular metal rack positioned in the center of the animal activity monitor was also recorded as goal-directed exploratory activity. Results of Experiment 1 showed that HA in POA exerted an inhibitory influence on general motor behaviors and also on goal-directed activity. Ipsilateral administration of HA-antagonists into HPC blocked the HA effect on behavior. Results of Experiment 2 showed that the administration of the HA-antagonists in any of the two doses used were not able to block the depressive actions on behavior caused by HA into POA. In conclusion, data suggest that POA is linked to the ipsilateral HPC through histaminergic influence to control behavioral patterns induced by novelty.

Animals↗
PubMed1983

Antagonistic effects of aldosterone on corticosterone-mediated changes in exploratory behavior of adrenalectomized rats.

The effect of aldosterone administration on exploratory activity of chronic adrenalectomized (10 days) male rats was investigated. Aldosterone (30 micrograms/100 g body wt sc) administered 1 hr or 30 min prior to the behavioral test failed to normalize disturbed exploratory activity of adrenalectomized rats, in contrast to the restoration observed after corticosterone, the naturally occurring glucocorticoid of the rat. Administration of the mineralocorticoid 30 min prior to corticosterone prevented the normalization of the behavioral response by the latter steroid. Administration of the same dose of aldosterone 30 min prior to a tracer amount of [3H]corticosterone effectively blocked cell nuclear uptake of radioactive-labeled hormone in the hippocampus. The specific action of corticosterone on exploratory behavior corresponds with the stringent specificity of the neuronal hippocampal corticosterone receptor system. Mineralocorticoid receptors do not seem to be involved in effects on this behavior. The antagonistic action of aldosterone is probably exerted by competitive binding to the corticosterone receptor.

Adrenalectomy↗
PubMed1989

Exploratory behavior, reaction to novelty, and proactive memory in rats with temporo-entorhinal connections disrupted.

The parahippocampal cortex is ascribed a key function in mediating reciprocal connections between neocortical association areas and the hippocampal formation. Within this complex the lateral entorhinal cortex (LEC) seems to stand out as an important interface exerting modulating influence upon cognition and memory by way of its connections with the hippocampal formation and temporal cortex (TC), respectively. The purpose of the present study was to compare effects of TC/LEC disruptions in a novelty test with results previously obtained in the same test following lateral perforant path (LPP) disruptions. Further, effects of TC/LEC lesions on proactive memory were examined, since a profound impairment in retroactive memory has previously been found. Rats bearing TC/LEC lesions or LPP lesions behaved differently in the novelty test. It was also shown that the impairment in proactive memory was less severe than the one seen in retroactive memory following TC/LEC lesions. The results are discussed in terms of a highly integrative role of LEC.

Animals↗
PubMed1998

Electrophysiological responses of nucleus accumbens neurons to novelty stimuli and exploratory behavior in the awake, unrestrained rat.

To establish a physiological correlate of goal-directed and reward-seeking non-operant behaviors, we studied the electrophysiological activity of NAcc neurons in unrestrained, naive Sprague-Dawley rats. Our results showed an inhibitory response in 21% (7/34) of the recorded NAcc neurons during spontaneous nosepoking behavior and in 16% (4/25) of the NAcc neurons when rats were fed with a favorite novel food morsel (popcorn). These data suggest that a subgroup of NAcc neurons is actively modulated during motivated behavior and during consummatory events resulting in a suppression of neuronal activity.

Animal Feed↗
PubMed1978

Exploratory behavior in rats following bilateral lesions of the anterodorsal caudate nuclei.

9 rats received bilateral lesions to the anterodorsal caudate nuclei and 9 rats underwent sham operation procedures. After recovery the subjects were observed in an apparatus allowing access to familiar or novel stimuli. The caudotomized rats spent a significantly greater proportion of time exploring the novel stimuli. The results were not consistent with the suggestions that following damage to the caudate nucleus animals were unresponsive to novelty, however, they did support earlier findings implicating the caudate nucleus in learning and memory processes.

Animals↗
PubMed1998

Influence of interleukin-1beta on exploratory behaviors, plasma ACTH, corticosterone, and central biogenic amines in mice.

Systemic administration of interleukin-1beta (IL-1beta) promoted behavioral changes in an open-field exploratory test. In particular, while the cytokine suppressed locomotor activities, these behaviors were not particularly sensitive to dosage differences. In contrast, dose-dependent biphasic variations that varied over time were evident with respect to the exploration of a novel container. Within this paradigm, the behavioral changes did not appear to be related to neophobia. In addition, despite the marked effects of IL-1beta on exploratory and locomotor behaviors, habituation/exploration in a free-running spontaneous alternation task was unaffected by the cytokine. In addition to the behavioral variations, IL-1beta dose-dependently increased plasma ACTH and corticosterone concentrations, and also induced several central monoamine alterations. In particular, IL-1beta increased the utilization of norepinephrine (NE) within the paraventricular nucleus, arcuate nucleus/median eminence, locus coeruleus, and prefrontal cortex, while the turnover of dopamine (DA) was evident in the arcuate nucleus/median eminence. It is suggested that although systemic IL-1beta treatment induces some stress-like effects, the profile of central neurochemical changes induced by the cytokine can be distinguished from psychological or processive types of stressors.

Adrenocorticotropic Hormone↗
PubMed1989

Exploratory behavior and the dual activity of some psychoactive drugs. Part 5. Alcohol.

Alcohol is reported to impair acquisition and learning processes and it is considered a depressant of the brain activities impairing rapidity and consistency of some behaviors. The experiments reported here are concerned with the exploratory performances of the already described subpopulations of Albino mice under the effect of alcohols of different types.

Alcoholic Beverages↗