Irrintzi Fernández-Aedo

α2-Adrenoceptors mediate the acute inhibitory effect of fluoxetine on locus coeruleus noradrenergic neurons

So far, the mechanisms underlying the action of selective serotonin reuptake inhibitors, such as fluoxetine, are not completely understood. Thus, to clarify if fluoxetine has any effect on noradrenergic transmission, we measured the spontaneous firing rate of noradrenergic neurons in the locus coeruleus both in vivo and in vitro using single-unit extracellular recordings. In anesthetized rats, fluoxetine (2.5-20 mg/kg, i.v.) reduced the firing rate in a dose-dependent manner, reaching a maximal inhibition of 55 +/- 5% with respect to the basal value. This effect was not only completely reversed by the alpha(2)-adrenoceptor antagonist, RX 821002 (0.2 mg/kg, i.v.), but also prevented by previous application of both idazoxan (0.05 and 0.1 mg/kg, i.v.) and RX 821002 (6.25 microg/kg, i.v). Furthermore, when noradrenaline was depleted from axon terminals by means of the injection of alpha-methyl-DL-tyrosine (250 mg/kg, i.p.) 24 h prior to the experiment, fluoxetine failed to inhibit locus coeruleus activity. In rat brain slices, perfusion with fluoxetine (100 microM for 5 min) did not modify the firing rate of locus coeruleus neurons (n = 7). We conclude that fluoxetine inhibits locus coeruleus neurons in vivo through a mechanism involving noradrenaline interacting with alpha(2)-adrenoceptors. However, the lack of effect on brain slices would seem to indicate that afferents to the nucleus may be involved in the observed inhibitory effect.

Role of GIRK channels on the noradrenergic transmission in vivo: an electrophysiological and neurochemical study on GIRK2 mutant mice

Dysfunctional noradrenergic transmission is related to several neuropsychiatric conditions, such as depression. Nowadays, the role of G protein-coupled inwardly rectifying potassium (GIRK)2 subunit containing GIRK channels controlling neuronal intrinsic excitability in vitro is well known. The aim of this study was to investigate the impact of GIRK2 subunit mutation on the central noradrenergic transmission in vivo. For that purpose, single-unit extracellular activity of locus coeruleus (LC) noradrenergic neurons and brain monoamine levels using the HPLC technique were measured in wild-type and GIRK2 mutant mice. Girk2 gene mutation induced significant differences among genotypes regarding burst activity of LC neurons. In fact, the proportion of neurons displaying burst firing was increased in GIRK2 heterozygous mice as compared to that recorded from wild-type mice. Furthermore, this augmentation was even greater in the homozygous genotype. However, neither the basal firing rate nor the coefficient of variation of LC neurons was different among genotypes. Noradrenaline and serotonin basal levels were altered in the dorsal raphe nucleus from GIRK2 heterozygous and homozygous mice, respectively. Furthermore, noradrenaline levels were increased in LC projecting areas such as the hippocampus and amygdale from homozygous mice, although not in the prefrontal cortex. Finally, potency of clonidine and morphine inhibiting LC activity was reduced in GIRK2 mutant mice, although the efficacy remained unchanged. Altogether, the present study supports the role of GIRK2 subunit-containing GIRK channels on the maintenance of tonic noradrenergic activity in vivo. Electric and neurochemical consequences derived from an altered GIRK2-dependent signalling could facilitate the understanding of the neurobiological basis of pathologies related to a dysfunctional monoaminergic transmission.

Contaminación microbiológica en humidificadores de sistemas de oxigenoterapia de alto y bajo flujo: una revisión sistemática

AIM To determine the risk of microbiological contamination with hospital use high- and low-flow bubbling humidifiers. METHODS A systematic literature review was carried out in 6 databases. Observational or experimental studies published between 1990 and 2016 were selected, written in English or Spanish, and in which microbiological contamination with hospital use high- and low-flow bubbling humidifiers was investigated. RESULTS A total of 12 articles were included: 4 analyzed the water from reusable humidifiers, 4 analyzed the water from prefilled system humidifiers, and the rest compared samples from both models. Microbial contamination was observed in all studies in which reusable humidifiers were evaluated, usually involving common bacteria from the skin flora, while potential pathogenic species were notified in 2 studies. No microbial contamination was isolated from reusable humidifiers, regardless of whether they had been consecutively used over time by a single patient or by several patients. CONCLUSION On one hand, there seems to be a low risk of contamination during the first weeks of use of prefilled humidifiers, which allows multiple use in different patients, without a risk of cross-contamination. On the other hand, it should be underscored that handling reusable humidifiers without correct aseptic measures can increase the risk of contamination; replacing reusable humidifiers with prefilled models therefore could be the safest option.

Dolor asociado a las técnicas de inserción de catéteres venosos y extracción de sangre arterial en el área de urgencias

OBJECTIVES To analyse vein catheterisation and blood gas test-related pain among adult patients in the emergency department and to explore pain score-related factors. METHOD An observational and multicentre research study was performed. Patients undergoing vein catheterisation or arterial puncture for gas test were included consecutively. After each procedure, patients scored the pain experienced using the NRS-11. RESULTS 780 vein catheterisations and 101 blood gas tests were analysed. Venipuncture was scored with an average score of 2.8 (95% CI: 2.6-3), and arterial puncture with 3.6 (95%CI 3.1-4). Iatrogenic pain scores were associated with moderate - high difficulty procedures (P<.001); with the choice of the humeral rather than the radial artery (P=.02) in the gas test and correlated to baseline pain in venipunctures (P<.001). Pain scores related to other variables such as sex, place of origin or needle gauge did not present statistically significant differences. CONCLUSIONS Vein catheterisation and blood gas test-related pain can be considered mild to moderately and moderately painful procedures, respectively. The pain score is associated with certain variables such as the difficulty of the procedure, the anatomic area of the puncture or baseline pain. A better understanding of painful effects related to emergency nursing procedures and the factors associated with pain self-perception could help to determine when and how to act to mitigate this undesired effect.