| 1. |
- Bentzer, Peter, et al.
(författare)
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Supersensitivity in rat micro-arteries after short-term denervation
- 1997
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 161:2, s. 125-133
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Tidskriftsartikel (refereegranskat)abstract
- Contractile responses to phenylephrine and high-K+ were investigated in vitro in microvascular preparations from the rat medial plantar artery, a branch from the saphenous artery, obtained after short-term denervation in vivo. Two groups of animals were studied: (1) animals undergoing surgical resection of the saphenous nerve, and (2) animals undergoing surgical resection of both the sciatic and saphenous nerves. The animals were operated on one side only. Microvascular preparations (diameter about 325 microns) were obtained 10 days after surgery. Vessels from the non-operated side served as controls. Immunocytochemistry showed a decreased number of both neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) immunoreactive nerve fibres in vessels after resection of the saphenous nerve only. Resection of both the saphenous and the sciatic nerve caused a complete loss of immunoreactive nerve fibres. Mechanical measurements were performed using a wire myograph. In vessels subjected to resection of the saphenous nerve the sensitivity to phenylephrine was similar to controls. Vessels denervated by resection of both the saphenous and sciatic nerves showed significant increases in phenylephrine and potassium sensitivity. When depolarized in high-K+ solution the denervated vessels showed an increased sensitivity to extracellular Ca2+. The results show that complete short-term denervation of the rat medial plantar artery in vivo causes a pronounced supersensitivity in the vascular smooth muscle. The supersensitivity appears not to be restricted to the sympathetic alpha-receptors but also associated with changes in the cellular excitation-contraction coupling. Such altered reactivity of the vascular smooth muscle may contribute to vascular disturbances observed in vivo after nerve damage or surgical denervation.
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| 2. |
- Johansson, C, et al.
(författare)
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Nitric oxide synthase inhibition blocks phencyclidine-induced behavioural effects on prepulse inhibition and locomotor activity in the rat.
- 1997
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Ingår i: Psychopharmacology. - 0033-3158. ; 131:2, s. 167-73
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Tidskriftsartikel (refereegranskat)abstract
- The ability of the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), to block the behavioural effects of the potent psychotomimetic, phencyclidine, was tested in rats using two different behavioural models. L-NAME was found to block both phencyclidine-induced disruption of prepulse inhibition of acoustic startle and phencyclidine-induced stimulation of locomotor activity. A selective action of L-NAME on the effects of phencyclidine was indicated, since L-NAME did not alter the effects of amphetamine, another potent psychotomimetic, in these behavioural models. These observations suggest that a nitric oxide-dependent mechanism may be involved in the effects of phencyclidine in the central nervous system.
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| 3. |
- Zhang, Jianhua, 1961, et al.
(författare)
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Repeated administration of amphetamine induces sensitisation to its disruptive effect on prepulse inhibition in the rat.
- 1998
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Ingår i: Psychopharmacology. - 0033-3158. ; 135:4, s. 401-6
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Tidskriftsartikel (refereegranskat)abstract
- Male Sprague-Dawley rats were repeatedly treated with amphetamine (AMP, 1 mg/kg, SC) at 3- day intervals for 15 days and tested for prepulse inhibition of acoustic startle after each treatment. This treatment regimen induced sensitisation in the animals as evidenced by a progressive increase in the disruptive effect of AMP on prepulse inhibition. Persistent changes in brain function was indicated, since an increase in disruptive effect was observed in sensitised animals also after a 22-day-long drug- and test-free period. The development of sensitisation was blocked by pretreatment with haloperidol (HPD, 0.1 mg/kg, SC), which suggests that sensitisation to the disruptive effect of AMP was dependent on dopamine (DA) D2 receptor activation. Furthermore, the development of sensitisation was blocked by adrenalectomy, which suggests that sensitisation was dependent also on circulating adrenal hormones. Increased DA-ergic activity has been implicated in the pathophysiology of schizophrenia and AMP-induced sensitisation to the neuronal functions that modulate prepulse inhibition may be an experimental model to investigate this hypothesis.
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| 4. |
- Eghbali, M, et al.
(författare)
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Hippocampal GABA(A) channel conductance increased by diazepam
- 1997
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 388:6637, s. 71-75
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Tidskriftsartikel (refereegranskat)abstract
- Benzodiazepines, which are widely used clinically for relief of anxiety and for sedation, are thought to enhance synaptic inhibition in the central nervous system by increasing the open probability of chloride channels activated by the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Here we show that the benzodiazepine diazepam can also increase the conductance of GABAA channels activated by low concentrations of GABA (0.5 or 5 microM) in rat cultured hippocampal neurons. Before exposure to diazepam, chloride channels activated by GABA had conductances of 8 to 53pS. Diazepam caused a concentration-dependent and reversible increase in the conductance of these channels towards a maximum conductance of 70-80 pS and the effect was as great as 7-fold in channels of lowest initial conductance. Increasing the conductance of GABAA channels tonically activated by low ambient concentrations of GABA in the extracellular environment may be an important way in which these drugs depress excitation in the central nervous system. That any drug has such a large effect on single channel conductance has not been reported previously and has implications for models of channel structure and conductance.
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| 5. |
- Vinter-Jensen, Lars, et al.
(författare)
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Acute contractile effects of epidermal growth factor on bladder smooth muscles. An in vivo and in vitro study in rats
- 1997
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Ingår i: Scandinavian Journal of Urology and Nephrology. - : Informa UK Limited. - 0036-5599 .- 1651-2065. ; 31:3, s. 231-235
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Tidskriftsartikel (refereegranskat)abstract
- Chronic treatment with epidermal growth factor (EGF) stimulates growth of all wall layers of the urinary tract in pigs and rats. Herein, we investigated the acute effects of EGF on detrusor smooth muscle activity. For in vivo examination, awake rats received EGF (75 micrograms/kg) intravenously and detrusor smooth muscle activity was monitored cystometrically. The EGF bolus caused no alteration in diuresis but a doubling of the micturition frequency, a 25% increase in micturition pressures, and increased irregular baseline contractile activity. For in vitro examination detrusor smooth muscle strips were exposed to EGF (1 microgram/ml). EGF caused contraction and increase in the spontaneous activity. In conclusion, EGF increases rat detrusor smooth muscle contractile activity in vivo and in vitro. The finding suggests that a direct effect of EGF on bladder smooth muscles is part of the genesis to the growth of the detrusor smooth muscle observed after chronic EGF treatment.
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| 6. |
- Abbas, Abdul-Karim, 1959, et al.
(författare)
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Bicarbonate-sensitive cysteine induced elevation of extracellular aspartate and glutamate in rat hippocampus in vitro
- 1997
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Ingår i: Neurochemistry International. - 0197-0186. ; 30:3, s. 253-259
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Tidskriftsartikel (refereegranskat)abstract
- The effect of different concentrations of cysteine (0.125, 0.25, 0.5 and 1 mM) on the net efflux of endogenous amino acids was studied by the incubation of rat hippocampal slices. Addition of cysteine (1 mM) in bicarbonate containing low K+ medium (5 min) selectively increased the basal net efflux of glutamate and aspartate by 370% and 396%, respectively. High K+ media (50 mM) containing cysteine (1 mM) evoked the net efflux of glutamate and aspartate by 1454% and 1019%, respectively. The corresponding effects in control slices without cysteine were 669% and 404%, respectively. No changes were observed on the concentrations of GABA, glutamine and taurine. The cysteine oxidation products, cysteine sulfinate (0.5 μM) and cystine (0.25 mM) were without effects. The effect of cysteine (0.5 mM) was dramatically reduced in media with no added bicarbonate/CO2. Thus, cysteine in a bicarbonate-sensitive manner selectively increases the extracellular concentration of excitotoxic amino acids in adult rat brain in vitro, possibly by interfering with the carrier-mediated glutamate uptake/ release
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| 7. |
- Abbas, Abdul-Karim, 1959, et al.
(författare)
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Bicarbonate-sensitive cysteine induced elevation of extracellular aspartate and glutamate in rat hippocampus in vitro
- 1997
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Ingår i: Neurochemistry International. - 0197-0186. ; 30:3, s. 253-259
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of different concentrations of cysteine (0.125, 0.25, 0.5 and 1 mM) on the net efflux of endogenous amino acids was studied by the incubation of rat hippocampal slices. Addition of cysteine (1 mM) in bicarbonate containing low K+ medium (5 min) selectively increased the basal net efflux of glutamate and aspartate by 370% and 396%, respectively. High K+ media (50 mM) containing cysteine (1 mM) evoked the net efflux of glutamate and aspartate by 1 454% and 1 019%, respectively. The corresponding effects in control slices without cysteine were 669% and 404%, respectively. No changes were observed on the concentrations of GABA, glutamine and taurine. The cysteine oxidation products, cysteine sulfinate (0.5 μM) and cystine (0.25 mM) were without effects. The effect of cysteine (0.5 mM) was dramatically reduced in media with no added bicarbonate/CO2. Thus, cysteine in a bicarbonate-sensitive manner selectively increases the extracellular concentration of excitotoxic amino acids in adult rat brain in vitro, possibly by interfering with the carrier-mediated glutamate uptake/ release
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| 8. |
- Lindeberg, Tony, 1964-, et al.
(författare)
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Analysis of brain activation patterns using a 3-D scale-space primal sketch
- 1999
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Ingår i: Human Brain Mapping. - 1065-9471 .- 1097-0193. ; 7:3, s. 166-94
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental problem in brain imaging concerns how to define functional areas consisting of neurons that are activated together as populations. We propose that this issue can be ideally addressed by a computer vision tool referred to as the scale-space primal sketch. This concept has the attractive properties that it allows for automatic and simultaneous extraction of the spatial extent and the significance of regions with locally high activity. In addition, a hierarchical nested tree structure of activated regions and subregions is obtained. The subject in this article is to show how the scale-space primal sketch can be used for automatic determination of the spatial extent and the significance of rCBF changes. Experiments show the result of applying this approach to functional PET data, including a preliminary comparison with two more traditional clustering techniques. Compared to previous approaches, the method overcomes the limitations of performing the analysis at a single scale or assuming specific models of the data.
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| 9. |
- Zhang, Jianhua, 1961, et al.
(författare)
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Involvement of the medial geniculate body in prepulse inhibition of acoustic startle.
- 1999
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Ingår i: Psychopharmacology. - 0033-3158. ; 141:2, s. 189-96
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Tidskriftsartikel (refereegranskat)abstract
- Prepulse inhibition of acoustic startle is the normal reduction in startle response to an intense auditory stimulus when this stimulus is immediately preceded by a weaker prestimulus. Previous studies have shown that several neuroanatomical structures and pathways in the brain are involved in the modulation of prepulse inhibition. In the present study, the functional importance of the medial geniculate body (MG) in the modulation of prepulse inhibition was investigated. To this end, in vivo brain microdialysis probes were used to infuse drugs locally into the MG of awake, freely moving rats simultaneously with startle response and prepulse inhibition measurements in the same animals. Intrageniculate infusion of the sodium channel blocker, tetrodotoxin, significantly reduced prepulse inhibition without affecting baseline startle amplitude. A similar effect was obtained after intrageniculate infusion of the GABA(B) receptor agonist, baclofen. In addition, intrageniculate infusion of muscimol, an agonist at the GABA(A) receptor complex, reduced prepulse inhibition, although this effect was obtained at a higher concentration of the drug compared to that of baclofen. These studies suggest that the MG is involved in the modulation of prepulse inhibition and that auditory signals relayed via the MG may be subjected to inhibitory control at this level, involving GABA neurotransmission.
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| 10. |
- Malmgren, Helge, 1945
(författare)
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Perceptual expectations and the learning of temporal sequences.
- 1996
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Ingår i: Philosophical Communications, Red Series. - 0347-5794. ; :35
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The paper starts with an overview of some central unsolved problems of intentionality. Partly basing my argument on an analysis of how the heard temporal Gestalt develops during the listenting to a musical phrase, I then present my model of mental simulation and associative learning through "natural resonance" in considerable detail.
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