A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions.

This global study, which has been coordinated by the World Meteorological Organization Global Atmospheric Watch (WMO/GAW) programme, aims to understand the behaviour of key air pollutant species during the COVID-19 pandemic period of exceptionally low emissions across the globe. We investigated the effects of the differences in both emissions and regional and local meteorology in 2020 compared with the period 2015-2019. By adopting a globally consistent approach, this comprehensive observational analysis focuses on changes in air quality in and around cities across the globe for the following air pollutants PM, PM, PMC (coarse fraction of PM), NO, SO, NOx, CO, O and the total gaseous oxidant (OX = NO + O) during the pre-lockdown, partial lockdown, full lockdown and two relaxation periods spanning from January to September 2020.

Dorsal and ventral dopaminergic innervation of the spinal cord: functional implications.

Several studies have demonstrated that a descending dopaminergic pathway innervates the dorsal and the intermediate gray matter of the spinal cord and have suggested that this pathway is involved in pain modulation and in the control of autonomic functions. Other studies have also demonstrated the presence of dopamine (DA) and DA metabolites as well as of DA receptors in the ventral cord. There is also evidence for the implication of DA in the control of motor functions at the spinal level.

A limited arthritic model for chronic pain studies in the rat.

Freund's adjuvant induced polyarthritis in rats has been used extensively to study pain processes of long duration. There are limitations of this model for chronic studies of pain/arthritis since the severe systemic changes provoke ethical concerns and also affect behaviour, physiology and biochemistry. Attempts to limit adjuvant-induced arthritis by plantar injection of the inoculum have been made.

Effect of aging on dopamine metabolism in the rat cerebral cortex: a regional analysis.

Age-related changes in the levels of dopamine (DA) and its metabolites were measured in seven cerebral cortical areas and in the striatum of 3, 10 and 27 month-old Sprague-Dawley rats. An age-related increase in DA levels was observed in the somatomotor (SM) cortex. In contrast, a decrease was observed in the temporal (T) cortex.

Further evidence for the involvement of the diencephalo-dopaminergic system in pain modulation: a neurochemical study on the effect of morphine in the arthritic rat.

Numerous studies from the past two decades suggest that the bulbospinal serotonergic and noradrenergic systems are involved in pain modulation at the spinal level. More recently the occurrence of a diencephalo-dopaminergic system has been demonstrated and there is evidence that this pathway may also participate in pain modulation. Several works have been devoted to the effect of morphine on the activity of the dopaminergic system in supraspinal areas but it is not at present known if opiates modify the activity of this system in the spinal cord sensory areas.

Increase in "pain sensitivity" induced by exercise applied during the onset of arthritis in a model of monoarthritis in the rat.

We have recently developed, in the rat, a model with a limited arthritic process for chronic pain studies. Intra-articular injection (0.05 ml) of complete adjuvant containing 300 micrograms Mycobacterium butyricum in the tibio-tarsal joint produces a predictable monoarthritis stable clinically and behaviourly from weeks 2 through 6 post-injection.

Simultaneous measurements of tryptophan and its metabolites, kynurenine and serotonin, in the superficial layers of the spinal dorsal horn. A study in normal and arthritic rats.

It has been demonstrated that 5-hydroxytryptamine (5-HT) is not the only neuroactive metabolite of tryptophan (TRP) in the CNS. The presence of kynurenine (KYN) and its metabolites has been reported in the brain of several mammalian species and the neuroactive properties of these compounds are now well established. In the present study, we report the identification of KYN in the superficial layers of the rat spinal dorsal horn.

Regional distribution of 3-O-methyl-DOPA in the cortex and subcortical structures in the rat: effect of aging.

Dihydroxyphenylalanine (DOPA) and its metabolite 3-O-methyl-DOPA (3-OMDOPA) have been identified as normal constituents in blood, CSF and brain in human and several animal species. In the present study, we report results of 3-OMDOPA measurements in seven cortical areas, hippocampus and striatum of young (3-month-old), middle aged (10-month-old) and aged (27-month-old) rats. 3-OMDOPA was identified in all the areas considered.

Effect of deafferentation on the levels of uric acid in the spinal cord of the rat.

In previous studies we reported that the rat spinal cord contains relatively high levels of uric acid and that the levels in a rat model of bilateral chronic pain, experimental adjuvant arthritis. In this report we evaluate the changes in UA in the unilaterally deafferented rat, a preparation which has also been used to study chronic pain. Uric acid was measured by high-pressure liquid chromatography with electrochemical detection in the spinal cord of rats that underwent unilateral, multiple cervical dorsal rhizotomy.

Age-related changes in dopaminergic and serotonergic indices in the rat forebrain.

Age-related changes in the content of dopamine (DA), homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in anterior cerebral cortex, hippocampus and striatum of the rat have been investigated using HPLC with electrochemical detection. A significant decrease in HVA was observed in the striatum and hippocampus of the aged (27 months) animals, as compared to the controls (2.4 to 2.

Absence of long-term changes in biochemical markers of monoaminergic systems afferent to the excitotoxically neuron-depleted somatosensory thalamus.

In a previous study, it was shown that, one month after kainic acid (KA) injection into the thalamus, afferents deprived of postsynaptic target neurons exhibit structural alteration, including the loss of synaptic vesicles. The present study was undertaken to determine whether these long-term morphological changes were associated with changes in biochemical markers of monoaminergic pathways. In situ injection of KA was performed into the right ventrobasal complex of the rat thalamus (VB).

A new microdissection technique for regional biochemical analysis of the rat spinal cord: serotonin, norepinephrine, dopamine and uric acid.

This report described a new microdissection procedure to evaluate the regional distribution of neuromediators in the rat spinal cord. Different segments are first divided into sagittal slices. From these, different grey and white matter regions can be microdissected.

Complex temporal changes in 5-hydroxytryptamine synthesis in the central nervous system induced by experimental polyarthritis in the rat.

The purpose of this study was to investigate modifications of 5-HT synthesis in a chronic pain model, the arthritic rat, at different times after the inoculation with Freund's adjuvant. This study confirms our previous findings that experimental induced polyarthritis is associated with a marked increase in free tryptophan levels in serum. During the acute phase of the disease (15-21 days after the adjuvant), the general increase in 5-HT synthesis observed in the CNS appeared to be related to an increase in tryptophan availability due to the elevation of free tryptophan in serum.

Increased norepinephrine and uric acid levels in the spinal cord of arthritic rats.

The purpose of the present study was to investigate whether the level of norepinephrine and its rate of disappearance after decarboxylase inhibition were modified in the spinal cord of a chronic pain model: the arthritic rat. Chromatographic studies allowing the simultaneous determination of norepinephrine and uric acid by means of HPLC with electrochemical detection are described. The norepinephrine and uric acid levels in the spinal cord were higher in arthritic rats than in normal rats.

Do acute or chronic tricyclic antidepressants modify morphine antinociception in arthritic rats?

In a chronic pain model, the arthritic rat, tricyclic antidepressants (TCAs) have been shown to clearly reduce behavioural signs of nociception. In the present work, using a test of acute nociception (vocalization threshold to graded foot pressure) in the same model, we evaluated the possible potentiation of morphine analgesia by 2 TCAs: amitriptyline (AMIT) and imipramine (IMIP). Using this test of acute nociception, we failed to demonstrate any analgesic effect of AMIT or IMIP given either acutely or chronically.

Reduction of arthritis and pain behaviour following chronic administration of amitriptyline or imipramine in rats with adjuvant-induced arthritis.

Tricyclic antidepressants (TCAs) are used extensively to treat chronic pain in man without an adequate explanation for their activity. The purpose of the present study was to investigate this problem by testing the effect of chronic TCAs in an animal pain model: the arthritic rat. Sprague-Dawley rats with adjuvant-induced arthritis were injected daily for 4 weeks with amitriptyline (10 mg/kg) or imipramine (10 mg/kg) or saline, beginning 21 days after the induction of arthritis.

Increase in 5-HT synthesis in the dorsal part of the spinal cord, induced by a nociceptive stimulus: blockade by morphine.

The effects of a nociceptive peripheral stimulus and/or morphine upon endogenous tryptophan levels (TRP), specific activity of tryptophan (S.A. of TRP) and serotonin (5-HT) synthesis in the dorsal and ventral spinal cord, the brainstem and the forebrain were investigated in anaesthetized rats.

The effect of morphine on the potassium evoked release of tritiated 5-hydroxytryptamine from spinal cord slices in the rat.

The effect of morphine on the potassium (40 mM) evoked release of exogenous [3H]5-HT from slices of the dorsal spinal cord of the rat was studied. The effects of in vitro applied morphine on the slices were compared to those produced by systemic morphine applied to the animals before preparation of the slices. The in vitro application of morphine (10(-6) to 10(-5) M) did not affect the release of [3H]5-HT.

The relationship between morphine analgesia and the activity of bulbo-spinal serotonergic system as studied by tolerance phenomenon.

The effect of various doses of acute morphine on both analgesia and 5-hydroxytryptamine (5-HT) synthesis in the brain and the spinal cord has been studied in rats rendered tolerant by chronic administration of the analgesic. In morphine-tolerant rats, the incorporation of tritiated-L-tryptophan (TRP) in the brain and the spinal cord was higher than in non-tolerant rats, but there was no significant difference in the synthesis rate of the newly formed 5-HT between the two groups. An acute dose of morphine (10 mg/kg) which induced a powerful analgesia and a large increase in 5-HT synthesis in non-tolerant rats, did not produce analgesia nor changes in 5-HT synthesis in tolerant rats.

Morphine analgesia and newly synthesized 5-hydroxytryptamine in the dorsal and the ventral halves of the spinal cord of the rat.

In the rat, morphine (5 mg/kg, s.c.) induced an increase in 5-hydroxytryptamine (5-HT) synthesis in the spinal cord.

Changes in total and free tryptophan levels in serum following acute morphine administration in arthritic rats.

In 'arthritic' rats a decrease in total tryptophan and an increase in free tryptophan levels was observed in serum after morphine administration (10 mg kg, s.c.).

Total and free serum tryptophan levels and brain 5-hydroxytryptamine metabolism in arthritic rats.

In rats suffering from experimentally induced arthritis produced by Freund's adjuvant, there is a marked decrease in total serum tryptophan levels and a marked increase in plasma-free tryptophan levels at both 15 and 21 days after the administration of the adjuvant. Tryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid levels are increased in the brain and the spinal cord at 15 days. However, 21 days after administration of the adjuvant these levels returned to normal values in the brain, but remained increased in the spinal cord.

Effect of acute administration of morphine on newly synthesized 5-hydroxytryptamine in spinal cord of the rat.

The effect of morphine (10 mg/kg, s.c.) on the rate of [3H]5-HT synthesis in brain and spinal cord following intravenous injection of [2H]tryptophan was studied in the rat.