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Bernard Calvino

Publications and source records attributed to Bernard Calvino.

6 recordsLinked to original sources
PubMed2006

Central pain control.

We describe the anatomic and physiological components involved in pain physiology, with the goal of providing readers with the background information needed to understand central pain control mechanisms. These include spinal segmental controls, supraspinal excitatory and inhibitory controls, and diffuse noxious inhibitory controls (DNICs). Pain is a subjective sensation produced by an emotionally unpleasant experience considered to originate in adaptive processes taking place within neuron networks located at various levels of the central nervous system. The intensity of the components of pain is influenced by the stimulus characteristics, patient-related factors, and the setting in which the stimulus occurs. The various components of pain and the psychological and neurophysiological mechanisms that underlie the affective dimension of pain are reviewed. As a conclusion, phantom pain is used to illustrate the role for physiological systems independent from those involved in the physiology of nociception and pain, such as the motor cortex. This example highlights the extreme complexity of pain and pain control systems in humans.

Animals↗
PubMed2006

[Neural basis of pain].

Main elements concerning the physiology of pain are described, as well as the structures of the nervous system at the origin of the central control of pain: peripheral fibres (small diameter myelinated A delta and unmyelinated C fibres); spinal ascending pathways; cerebral structures relaying nociceptive information (medial and ventro-postero-lateral thalamic relays); SI and SII cortical areas; spinal segmentary and supraspinal excitatory and inhibitory controls; diffuse noxious inhibitory controls (DNIC). Chronic pain is a result of two processes: peripheral and central sensitization, in relation with inflammation and nerve injury at peripheral level and with neuroplasticity at central level. Neurotrophins, mainly NGF and BDNF and their receptors (LNTR, TrkA and TrkB) are involved in these processes. Pain is a result of an unpleasant emotional experience: its various components, mainly the emotional one, may be increased or decreased considering the different characteristics of the stimulus and of the affective state of the patient, as well as the context in which this stimulus is applied. The role of physiological systems, unconnected with those classically involved in the physiology of nociception and pain, such as the motor cortex in phantom limb pain, are described in conclusion, to focus on the extreme complexity of the control systems of pain in humans.

Chronic Disease↗
PubMed1992

Chronic pain induces a paradoxical increase in growth hormone secretion without affecting other hormones related to acute stress in the rat.

In several diseases chronic pain is associated with long-lasting pathophysiological responses which differ strongly from those observed in acute situations. When persisting, acute pain often results in physical and psychological stress which may in turn aggravate the initial pathological state. In the present work we examined the secretory patterns of pituitary hormones related to acute stress (growth hormone (GH), prolactin (PRL) and beta-endorphin (beta-END)) in rats during the phase of Freund adjuvant-induced arthritis (AIA, a model used for chronic pain studies) when chronic pain is maximum (14 and 21 days, postinoculation (PI)). Using radio-immunoassay hormones were measured in plasma samples taken every 30 min for 7 h in free-moving rats 14 and 21 days after Freund adjuvant or vehicle injection and in control animals. The total amount of GH secretion was higher at 14 and 21 days PI in AIA rats as compared to vehicle-treated and control animals, and the pulsatility of GH secretory pattern was not modified by AIA. PRL and beta-END secretion were not significantly different in arthritic rats as compared to controls. These results show that GH, PRL and beta-END responses induced by acute stress are not observed during the AIA phase when chronic pain is maximum. Thus, in our experimental conditions, beta-END and PRL do not seem to be good plasma markers of chronic pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Dorsal horn (convergent) neurones in the intact anaesthetized arthritic rat. II. Heterotopic inhibitory influences.

Recordings were made from dorsal horn neurones in the spinal cord and trigeminal nucleus caudalis of intact anaesthetized rats. These rats had been rendered polyarthritic by s.c. injection of Mycobacterium butyricum suspended in oil into the base of the tail. The experiments were carried out during the acute phase of the illness (3-4 weeks post inoculation) during which hyperalgesia occurred. The disease mainly affected the hind paws and the tail and, to a lesser extent, the forepaws. The facial area of the animals was not at all affected. As described in a previous paper, recordings from lumbar dorsal horn neurones revealed that two subpopulations could be described on the basis of their electrophysiological characteristics. Namely, 'typical' units which include convergent, non-noxious and proprioceptive neurones and which have properties essentially similar to those found in healthy rats, and 'atypical' cells which have no counterpart in healthy rats and which include convergent and non-noxious neurones. All the typical convergent neurones were inhibited by noxious stimuli applied to heterotopic body areas, whereas typical non-noxious and proprioceptive neurones were not; these observations are similar to those described in healthy rats as diffuse noxious inhibitory controls (DNIC). However, it was also found that 88% of the atypical convergent and 85% of the atypical non-noxious cells were inhibited by various heterotopic stimuli. The most important observation was that gentle stimulation such as mild pressure applied to the inflamed contralateral ankle joint--a stimulus intensity which has never been found to be effective in healthy animals--was capable of triggering inhibition of both typical and atypical convergent neurones. Recordings from trigeminal nucleus caudalis neurones revealed that the entire population presented essentially the same properties as those observed in healthy animals in terms of activity evoked by natural or electrical stimulation of their excitatory receptive fields. The activity of non-noxious neurones was never modified by any heterotopically applied stimuli. By contrast, all convergent neurones were inhibited by heterotopic stimuli, noxious (52 degrees C, pinch) or non-noxious (light and mild pressure), applied to inflamed areas. While the inhibition triggered by noxious stimuli was reminiscent of that observed in healthy rats, the inhibition triggered by non-noxious mechanical stimuli was related to the inflammatory state of the part of the body stimulated, the most sensitive areas being the hind paws.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1987

Dorsal horn (convergent) neurones in the intact anaesthetized arthritic rat. I. Segmental excitatory influences.

Recordings were made from dorsal horn neurones in intact anaesthetized rats rendered polyarthritic by s.c. injection into the base of the tail, of Mycobacterium butyricum suspended in oil; the experiments were carried out during the acute phase of the illness (3-4 weeks post inoculation) during which hyperaesthesia occurred. The majority (60.8%) of the neurones studied had properties close to those of corresponding groups of units in healthy rats. These 'typical' neurones could be subdivided into convergent (13.2%), non-noxious (34.4%) and proprioceptive (13.2%) units. By contrast, and in agreement with a previous study in the unanaesthetized spinal arthritic rat, the segmental electrophysiological characteristics of the remaining large proportion of neurones were changed both in terms of the size and distribution of their excitatory receptive fields and their responsiveness to peripheral stimuli; these were designated as 'atypical' neurones. According to their electrophysiological properties, these neurones were differentiated as atypical convergent (27.8%) and atypical non-noxious (11.4%) units. The main qualitative difference between the typical and atypical neurones was that the atypical had an additional receptive field on the oedematous ipsilateral ankle and, in several cases, showed high levels of background activity with sometimes dramatic increases. By comparison with neurones recorded in healthy rats, quantitative data revealed other modifications: typical and atypical convergent neurones and atypical non-noxious neurones had larger classical excitatory receptive fields; while C-fibre responses evoked by transcutaneous electrical stimulation were facilitated in the case of typical convergent neurones, 47% of the atypical convergent neurones had no C-fibre responses, and when present (53%) the threshold for obtaining these C-fibre responses was higher with suprathreshold stimuli producing a minimal number of spikes; in these cells, gentle mechanical stimuli gave rise to high rates of firing which sometimes resulted in dramatic, long lasting after-discharges. The possibility that typical convergent, atypical convergent and atypical non-noxious neurones were derived from the homogeneous population of convergent neurones in the healthy rat is discussed; the atypical properties could be the result of a change in the characteristics of convergent neurones, resulting from arthritis.

Animals↗