Bruxismo y dolor crónico orofacial / Bruxism and chronic orofacial pain

En el estado actual del conocimiento sobre los factores y mecanismos del bruxismo se han ido abandonando las posiciones de la relación causal estrecha entre oclusión y bruxismo, pero sin descartarla como factor a tener en cuenta por ser parte del complejo proceso perceptivo periférico. Crece la evidencia experimental del papel clave que juegan los mecanismos centrales excitadores e inhibidores de la actividad muscular y cuando se ha vuelto crónico de muy poca posibilidad de solución; salvo el efectgo placebo o la remisión espontánea. El dolor crónico orofacial no guarda una relación causal demostrable con el bruxismo pero, sin embargo, puede coexistir o no. No obstante, como factor irritativo crónico sobre las estructuras profundas perceptivas es muy probable que contribuya a establecer circuitos centrales por la acción neuroendócrina y de neuropéptidos vinculados a la acción neuromuscular y al dolor por el efecto de hiperalgesia central resultante de la estimulación repetitiva (wind up). Por ello, es muy importante el diagnósitoc multifactorial temprano y la terapia biaxial que es interactiva. La llamada vinculación del stress emocional con el dolor es parte de un fenómeno más complejo con los que se llaman fenómenos vivenciales como los culturales; estilo de enfrentamiento; rasgos de personalidad; ansiedad; angustia, miedo y la vinculación de la depresión con el dolor que interactúan con los neuroendócrinos. Dado que el dolor crónico (como otras enfermedades crónicas) es una condición para la cual usualmente la cura no es posible, el objetivo de la mayor parte de los casos de dolor crónico es un programa de tratamiento rehabilitativo más que curativo, para evitar la discapacitación y/o el padecimiento. Estos aspectos deben tratarse con una buena relación interpersonal, una serie de tests y una entrevista estructurada que permita la terapia cognitiva

Correlation between concomitant theta waves in nucleus reticularis pontis oralis and in hippocampus, thalamus and neocortex during dreaming in rats

Theta waves, which are the main electrophysiological expression of dreaming activity in many brain structures of rats, often undergo specific changes in voltage and frequency according to the oniric patterns. Much is known about their mechanisms but little is known regarding their origin, which has been ascribed to a specific activation of either the reticular formation or the septal nuclei or nucleus reticularis pontis oralis. In the present study, rats were prepared for chronic recording of the electro-oscillograms of cortical areas 10, 3 and 17, of hippocampal CA1 and CA3 fields, of nucleus reticularis thalami, nucleus reticularis pontis oralis and occasionally of nucleus reticularis caudalis. Head, rostrum, eye and forelimb movements were also recorded, so that the oniric behaviors could be precisely identified. The scatter diagrams and the corresponding correlation coefficients (r) of the voltage of concomitant waves were determined for each possible pair of leads. The potentials were analyzed at a frequency of 256 Hz over a period of 1 to 3 sec. A very high degree of correlation was observed between theta waves in nucleus reticularis pontis oralis, hippocampal fields and nucleus reticularis pontis caudalis; sometimes r approached unity. Although these data cannot be taken as proof of nucleus reticularis pontis oralis being the source of theta waves, they are at least compatible with this hypothesis.

Disruptive effect of the mesencephalic reticular formation on tonic immobility in guinea pigs

Cholinergic stimulation of the mesencephalic reticular formation with carbachol impairs the induction of tonic immobility (TI) by restreining maneuvers and reduces the duration of immobility episodes in guiena pigs TI which permits the animal to evaluate the best6 time for escape. It is possible that this monitoring inolves cirucits and neurotransmitters other than the ascending cholinergic system origination in the mesencephalic reticular formation

Effects of mesencephalic lesion on the histomorphology of testis and spermatogenesis.

Mesencephalic reticular formation lesions were produced bilaterally by using two epoxy-coated stainless steel electrodes. Electrolytic lesions resulted in atrophy of testes, and decreased spermatogenesis. Seminiferous tubules of lesioned rats were characterised by a general decrease in the number of cells from different generation of germinal epithelium, empty spaces, degeneration of spermatogonia, degeneration of spermatocytes I and of young spermatids. There were significant reductions in weights of the testes (P less than 0.01). Similarly the areas of cross-sections of seminiferous tubules were significantly reduced (P less than 0.05). Another note-worthy feature was a gross reduction in the complete cross section count of interstitial cells. The study strongly suggests that the mesencephalic reticular formation influences the testes and spermatogenesis.

Experimental spike and wave EEG pattern from thalamic stimulation in anaesthetized juvenile monkeys.

A bilaterally synchronous 3/sec spike and wave pattern in the EEG can be obtained during stimulation of the nucleus medialis dorsalis (nMD) and nucleus paracentralis (nPC) of the thalamus, in lightly anaesthetized juvenile monkeys. The spike and wave EEG patterns have a frequency of 2 1/2 to 3Hz and occur during low frequency stimulation, without continuing into the post-stimulatory phase. Stimulation of the mesencephalic reticular formation (MRF) at higher voltages inhibits the thalamic-induced spike and wave response. This finding has heuristic significance, as activating stimuli arrest the wave and spike EEG pattern of human absence (petit mal epilepsy) seizures. The study also demonstrates the morphological similarity of the 3/sec spike and wave thalamic induced response in experimental and clinical absence states as well as similarities in their alterations with different levels of activation.

Central nervous control of venous tone. III. Responses of capacitance and resistance vessels of skin to bulbar and hypothalamic stimulation.

Electrical stimulation of 350 points in the bulbar formation of 35 dogs under chloralose anaesthesia demonstrated the presence of sites producing increase or decrease of systemic arterial pressure (SAP) in the same general morphological limits of bulbar pressor and depressor regions as described by earlier authors. Simultaneous recording of pressure changes in the cutaneous vessels however demonstrated that pressure changes in these vessels did not correspond to the pressor or depressor effects of the SAP. Instead, responses were obtained in which pressures in cutaneous capacitance and resistance vessels followed a trend which was opposite in direction and magnitude to that of SAP. Thus there were 30 depressor sites which produce increase in cutaneous vessel pressure and 23 pressor sites which produced a fall in cutaneous vessel pressure. For a marked rise in the SAP, only 62 sites elicited equally marked increase in both capacitance and resistance vessel pressure, while another 52 elicited only a small increase of equivalent magnitude in the capacitance and resistance vessels. Stimulation of 84 points produced dissimilar effects on capacitance and resistance vessels out of which 38 elicited moderate increase in resistance vessel tone with minimal changes in the capacitance vessel tone, while 46 points elicited moderate increase in capacitance vessel tone with only a small increase in the resistance vessel tone. These points were diffusely admixed in the bulbar reticular formation. Effects which were exclusive to the capacitance and resistance vessels of skin, singly or in combination, without affecting the SAP were elicited from 12 points while another 28 points produced marked rise or fall of systemic arterial pressure without affecting the cutaneous vessels. These observations suggest that the neuronal organisation regulating cardiovascular activities at the bulbar level is quite complex having the capacity to generate varying activities in different components of the vascular circuits by differentially altering the discharge of the efferent sympathetic fibres on the one hand, and marked selectivity of action on any particular vascular bed or circulatory component on the other hand. Stimulation of 93 points in the hypothalamus produced similar patterns of response as obtained from medulla oblongata. In addition, stimulation of 6 points in the anterior hypothalamus produced a distinctive response accompanied by dilatation of cutaneous resistance and capacitance vessels with marked increase in respiratory rate and minimal changes in the SAP. This type of response which resembled the physiological response employed for heat loss was not obtained from any stimulation site in the medulla oblongata.