Spinal LTP induced by sciatic nerve electrical stimulation enhances posterior triangular thalamic nociceptive responses.

Long-term potentiation (LTP) can be induced by electrical stimulation and gives rise to an increase in synaptic strength at the first relay. This phenomenon has been associated with learning and memory and also could be the origin of several pathological states elicited by an initial strong painful stimulus, such as some forms of neuropathic pain. We used high-frequency electrical stimulation of the sciatic nerve in anesthetized rats to produce spinal LTP. To evaluate the effect of spinal LTP on the activity of neurons in the posterior triangular nucleus of the thalamus (PoT), we applied an electrical stimulation (40 stimuli; 1ms; 0.5Hz; 1.5mA) to cutaneous tissues at 10-min intervals during at least 3h. In the majority of cases, PoT cells did not respond to cutaneous stimulation before LTP, but 50min after LTP induction PoT cells progressively began responding to the cutaneous stimulation. Furthermore, after 3h of LTP induction, PoT neurons could respond to cutaneous stimulation applied to different paws. Interestingly, the conduction velocities for the receptive field responses from the paw to the PoT cells were compatible with those of Aδ-fibers. Since PoT cells project to the insular cortex, the progressive increase in PoT activity and also the progressive unmasking of somatic receptive fields in response to LTP, place these cells in a key position to detect pain stimuli following central sensitization.

Functional interactions between the paraventricular hypothalamic nucleus and raphe magnus. A comparative study of an integrated homeostatic analgesic mechanism.

This work compares the effects of electrical stimulation of the paraventricular hypothalamic nucleus (PVN) and the raphe magnus nucleus (RMg) on the single-unit response from dorsal spinal cord neurons activated by nociceptive receptive field stimulation. We evaluated the effects of stimulating the PVN or RMg individually or simultaneously, as well as PVN stimulation after RMg electrolytic lesion. PVN or RMg stimulation suppressed the A-delta, C fiber, and postdischarge, and we demonstrated that their simultaneous stimulation increases the duration and intensity of suppressive effects. RMg lesion increased the peripheral responses, but PVN stimulation continued to be suppressive. The intrathecal administration of 20 µl of a 10⁻5 M solution of a specific oxytocin antagonist strongly reduced the PVN effects, and 20 µl of 10⁻6 M naloxone significantly reduced the RMg suppression of receptive field responses. Some spinal cord cells presented a short-latency, evoked action potential (6.8 ms and a variability of ±0.5 ms) produced by the RMg stimulation. This is interpreted as a direct postsynaptic action of the RMg on the spinal cord cells. We never found similar responses produced by the PVN, and therefore, we propose that the PVN effects are presynaptic. Finally, the immunohistochemical experiments confirmed the oxytocinergic and the vasopresinergic innervation used by the PVN projection to the RMg, and they raise the possibility that other neurotransmitters are involved. We conclude that the PVN and the RMg form part of a homeostatic analgesic mechanism acting on the same spinal cord cells to block the noxious information, but using different mechanisms. Both structures, and others, contribute to the homeostatic mechanism of endogenous analgesia.

Identification of a novel, multifunctional beta-defensin (human beta-defensin 3) with specific antimicrobial activity. Its interaction with plasma membranes of Xenopus oocytes and the induction of macrophage chemoattraction.

Previous studies have shown the implication of beta-defensins in host defense of the human body. The human beta-defensins 1 and 2 (hBD-1, hBD-2) have been isolated by biochemical methods. Here we report the identification of a third human beta-defensin, called human beta-defensin 3 (hBD-3; cDNA sequence, Genbank accession no. AF295370), based on bioinformatics and functional genomic analysis. Expression of hBD-3 is detected throughout epithelia of many organs and in non-epithelial tissues. In contrast to hBD-2, which is upregulated by microorganisms or tumor necrosis factor-alpha (TNF-alpha), hBD-3 expression is increased particularly after stimulation by interferon-gamma. Synthetic hBD-3 exhibits a strong antimicrobial activity against gram-negative and gram-positive bacteria and fungi, including Burkholderia cepacia. In addition, hBD-3 activates monocytes and elicits ion channel activity in biomembranes, specifically in oocytes of Xenopus laevis. This paper also shows that screening of genomic sequences is a valuable tool with which to identify novel regulatory peptides. Human beta-defensins represent a family of antimicrobial peptides differentially expressed in most tissues, regulated by specific mechanisms, and exerting physiological functions not only related to direct host defense.

[Unnecessary attendance at a hospital emergency service and linked factors]. / Inadecuación de las visitas a un servicio de urgencias hospitalario y factores asociados.

OBJECTIVES: To adapt to our environment a protocol that assesses the adequacy of attendance at a hospital emergency service (HES), in order to calculate the frequency of unnecessary attendance and to analyse possible linked factors. DESIGN AND SETTING: Qualitative study using retrospective cross-sectional analysis of 269 records of patients attended at a third-level HES in Granada. METHODS: A heterogeneous group of experts (4 HES doctors and 4 PC doctors) agreed a scale for identifying unnecessary attendance at HES, which was then applied to a randomised sample of records of patients seen in the preceding year. An analysis was made of the proportion of unnecessary attendance and various associated factors: demographic variables, accessibility and variables involving the reason for consultation. The statistical techniques used were: confidence intervals to calculate percentage of unnecessary attendance, kappa index for agreement among observers on using the scale, and multiple logistic regression to analyse the association between unnecessary attendance and the factors studied. RESULTS: Inter-observer concordance for 73% of the scale. 35% of visits unnecessary (95% CI, 29-41%). Unnecessary use of the HES was more by women (OR, 1.94, p = 0.023), patients from unreformed health areas (OR, 2.02, p = 0.028), those coming from home without having seen their general practitioner (OR, 2.54, p = 0.08), those who had had for longer the condition occasioning the attendance, and medical-type emergencies (OR, 1.52, p = 0.022). CONCLUSIONS: More studies to test the reliability of the scale need to be performed. The apparent deduction is that a special reverence for emergency hospital care still exists and that this is sometimes used to side-step waiting-lists.

[Indicators of anxiety and depression in subjects with different kinds of diet: vegetarians and omnivores]. / Indicadores de ansiedad y depresión en sujetos con diferentes tipos de alimentación: vegetarianos y omnívoros.

The following study, one of the first done in Puerto Rico, investigate the different kinds of diet and the level of anxiety and depression that the subjects present. The sample consists of 80 subjects between 25 and 70 years age divided into two main groups (vegetarian versus no vegetarian) depending their diet consumption. The basic findings in the three psychological tests given (IDARE-1, IDARE-2 and CES-D) to the subjects demonstrate significant differences in anxiety and depression between groups. More anxiety and depression where reported in the no vegetarian groups in comparison with the vegetarian groups. In addition, diet analysis found more nutritional antioxidant agents levels in the vegetarian group in comparison with the no-vegetarian group.

Indicadores de ansiedad y depresión en sujetos con diferentes tipos de alimentación: vegetarianos y omnívoros / Indicators of anxiety and depression in subjects with different kinds of diet: vegetarians and omnivores

The following study, one of the first done in Puerto Rico, investigate the different kinds of diet and the level of anxiety and depression that the subjects present. The sample consists of 80 subjects between 25 and 70 years age divided into two main groups (vegetarian versus no vegetarian) depending their diet consumption. The basic findings in the three psychological tests given (IDARE-1, IDARE-2 and CES-D) to the subjects demonstrate significant differences in anxiety and depression between groups. More anxiety and depression where reported in the no vegetarian groups in comparison with the vegetarian groups. In addition, diet analysis found more nutritional antioxidant agents levels in the vegetarian group in comparison with the no-vegetarian group