Neuroscience letters
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Neuroscience letters · Dec 2002
Comparative StudyCross-tolerance between the different mu-opioid receptor agonists endomorphin-1, endomorphin-2 and morphine at the spinal level in the rat.
In the present study we investigated the development of tolerance to an antinociceptive effect after intrathecal administration of endomorphin-1, endomorphin-2 and morphine in tail-flick and paw pressure tests. We also assessed cross-tolerance between the antinociceptive effects of the two endogenous mu-opioid receptor agonists - endomorphins and morphine. The tolerance developed on day 3 after i.th. injection of both endomorphins, endomorphin-2 (18, 36 nmol), endomorphin-1 (16 nmol). ⋯ In contrast, no cross-tolerance was observed after administration of endomorphin-2 in rats tolerant to endomorphin-1. In rats tolerant to endomorphin-2, the antinociceptive effect of morphine and endomorphin-1 was attenuated in both the tests used. Our results suggest that the three ligands of mu-opioid receptors probably act via different subtypes of the mu-opioid receptor.
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Neuroscience letters · Nov 2002
Comparative StudyProtective effects of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin against traumatic brain injury-induced cognitive deficits and neuropathology in adult male rats.
To further investigate the efficacy of 5-HT(1A) receptor agonism on functional and histological outcome in traumatically-brain injured (TBI) rats, a single intraperitoneal injection of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.1, 0.5, or 1.0 mg/kg) or vehicle was given 15 min after controlled cortical impact or sham injury. Function was assessed by established motor and cognitive tests on post-operative days 1-5 and 14-18, respectively. ⋯ The administration of 8-OH-DPAT (0.5 mg/kg) attenuated spatial acquisition deficits and reduced hippocampal CA(3) cell loss vs. vehicle (P < 0.05). These data augment published reports that 5-HT(1A) receptor agonists confer neuroprotective effects after experimental TBI.
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Neuroscience letters · Nov 2002
Effects of lignocaine blockades and kainic acid lesions in the Bötzinger complex on spontaneous expiratory activity and cough reflex responses in the rabbit.
We investigated the role played by Bötzinger complex (Böt. c.) region in the genesis of the cough reflex and expiratory drive to expiratory neurons of the caudal ventral respiratory group (cVRG) in pentobarbitone-anesthetized spontaneously breathing rabbits. Phrenic nerve and abdominal muscle activities were monitored. Microinjections (30-50 nl) of 4% lignocaine or 4.7 mM kainic acid in the Böt. c. region suppressed spontaneous rhythmic expiratory activity as well as the inspiratory and expiratory components of the cough reflex evoked by mechanical stimulation of the tracheobronchial tree. These results support the view that neurons located in the Böt. c. have an important role not only in the genesis of the synaptic drive to cVRG expiratory neurons, but also in determining the overall characteristics of the cough motor pattern.
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Neuroscience letters · Sep 2002
Developmental sequence in the acquisition of anticipation during a new co-ordination in a bimanual load-lifting task in children.
The aim of this experiment was to test the capacity of children to develop anticipation at various stages of their growth. We studied the learning process of an artificial co-ordination by means of a procedure of double unloading in two groups of children, and a group of adults. ⋯ A difference in learning dynamics, but also in the final level of performance, is reported between children aged 5-6 and children aged 7-8 years. The improvement occurring at the age of 7 years probably indicates maturation of internal representations, favourable to the faster setting up of operational anticipated control.
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We used non-linear analysis to investigate the dynamical properties underlying the EEG in the model of Sahaja Yoga meditation. Non-linear dimensional complexity (DCx) estimates, indicating complexity of neuronal computations, were analyzed in 20 experienced meditators during rest and meditation using 62-channel EEG. When compared to rest, the meditation was accompanied by a focused decrease of DCx estimates over midline frontal and central regions. ⋯ The DCx estimates negatively correlated with theta-2 and alpha-1 and positively with beta-3 (22-30 Hz) band power. It is suggested that meditative experience, characterized by less complex dynamics of the EEG, involves 'switching off' irrelevant networks for the maintenance of focused internalized attention and inhibition of inappropriate information. Overall, the results point to the idea that dynamically changing inner experience during meditation is better indexed by a combination of non-linear and linear EEG variables.