Behavioural brain research
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The effects of R(+)-8-hydroxy-dipropylaminotetralin (8-OHDPAT) administration into the dorsal raphe nucleus (DRN) or bilaterally into the dorsal hippocampus (HIP) on fear behavior in a modified version of the light-dark transitions test and regional brain monoamines (NA, DA, 5-HT) and their metabolites (MHPG, DOPAC, 5-HIAA) in the hypothalamus, midbrain central gray matter, amygdala, hippocampus and pons were examined. The experiments were performed on 36 male, 3-month old Wistar rats. Administration of 8-OHDPAT (200 ng) into the DRN reduced time out from the illuminated part of the chamber and time of motionless behavior in the illuminated part, increased the number of returns from the dark to illuminated part and number of head dipping from the dark to illuminated part without effect on time of motionless behavior in the dark part and on time of locomotor activity in the illuminated as well as in dark part of the chamber. ⋯ Concentrations of 5-HT, 5-HIAA and 5-HIAA/5-HT ratio were unchanged. The results obtained indicate that 8-OHDPAT acting on the pre-synaptic 5-HT1A receptors decreases fear behavior and acting on 5-HT1A post-synaptic receptors increases fear behavior in the light-dark transitions test. The neurochemical base of anxiolytic and anxiogenic effects evoked by 8-OHDPAT is being discussed.
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The purpose of this study was to develop a model of unilateral cervical (C4-C5) spinal cord contusion injury in the rat and to characterize the functional and histological consequences following three injury levels using a new weight-drop spinal cord injury device. We evaluated forepaw/forelimb and hindlimb functions by: (1) a horizontal ladder beam measuring paw misplacements and slips; and (2) the forelimb preference test which measures the forelimb used for pushing off to rear, for support, and to land on after rearing. Rats with a mild spinal cord injury displayed primarily a forepaw deficit (forepaw misplacements) for 8 weeks after injury. ⋯ The lesion encompassed the entire dorsolateral, lateral and ventrolateral funiculi with some disruption of the ventral funiculus. There was more significant gray matter necrosis compared to rats with either a mild or moderate injury. Thus, the spinal cord injury device we used may be useful for studying graded cervical spinal cord injury in rats and potential treatments or interventions, because both the behavioral and histological effects are reproducible and consistent.
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This review describes a series of animal experiments that investigate the role of endogenous adenosine (AD) in sleep. We propose that AD is a modulator of the sleepiness associated with prolonged wakefulness. More specifically, we suggest that, during prolonged wakefulness, extracellular AD accumulates selectively in the basal forebrain (BF) and cortex and promotes the transition from wakefulness to slow wave sleep (SWS) by inhibiting cholinergic and non-cholinergic wakefulness-promoting BF neurons at the AD A1 receptor. ⋯ Might AD also produce modulation of activity of neurons that have sleep selective transcriptional (Fos) and discharge activity in the preoptic/anterior hypothalamus zone? Whole cell patch clamp recordings in the in vitro horizontal slice showed fast and likely GABAergic inhibitory post-synaptic potentials and currents that were greatly decreased by bath application of AD. Adenosine may thus disinhibit and promote expression of sleep-related neuronal activity in the POAH. In summary, a growing body of evidence supports the role of AD as a mediator of the sleepiness following prolonged wakefulness, a role in which its inhibitory actions on the BF wakefulness-promoting neurons may be especially important.
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A large decrease in brain nicotinic receptor levels occurs in Alzheimer's disease, relative to muscarinic and other receptors. Neurons possessing high affinity nicotinic receptors seem particularly vulnerable. The low affinity nicotinic receptors which selectively bind alpha-bungarotoxin are not significantly affected. ⋯ Psychological tests on healthy young male subjects indicate a positive effect of DMXBA on some measures of cognition. While DMXBA is a much weaker partial agonist on human alpha7 receptors than upon rat alpha7 receptors, its 4-hydroxy metabolite has been shown to have excellent efficacy on both receptors. Thus, some of the physiological and behavioral effects of GTS-21 may be due to the actions of this primary metabolite.
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The acoustic startle response (ASR) in rats is mediated by an oligosynaptic pathway from the cochlea via the brainstem to spinal and cranial motoneurons. The present study tested whether the superior olivary complex (SOC) plays a role in the mediation of the ASR. ⋯ The integrity of PnC which is adjacent to the SOC was confirmed by testing the tactile startle response which was not affected by SOC lesions. We suggest that the SOC is necessary for a full expression of the ASR and discuss possible auditory input structures involved in the mediation of the ASR.