Role of intraosseous receptors in afferent and motor reaction modulation

Abstract

Acute experiments on cats demonstrated facilitation effects of afferent reactions, and segmentary motor reactions during stimulation of sciatic nerves and inhibition of corticofugal motor reactions induced by electrical stimulation of ilium osteoreceptors. Key Words: nociception; intraosseous receptors; radicular syndromeThe osteoreceptor system remains one of the least studied parts of sensory system physiology. This might be due to the fact that so far no holistic concept has yet emerged regarding its role in physiological functions and its participation in the pathogenesis of somatic and visceral diseases [3,4]. Published data suggest that overstimulation of intraosseous receptors (e.g., during increased intraosseous pressure) may cause disturbances in sensorirnotor reactions, most clearly manifested in the general segments of spinal innervation [1][2][3][4]. Increased intraosseous afferentation is thought to play an essential role in the development of neurologic manifestations of lumbar osteochondrosis, prompting the present study aimed at elucidating the effect of osteoreceptor system stimulation on the formation of evoked potentials (EP) in the cerebral cortex and electromyographic reactions for discrete electrostimulations of the sciatic nerve. MATERIALS AND METHODSEP in the focus of maximum activity of the first sensorimotor area of the cerebral cortex and the electromyogram (EMG) of femora/ muscles during sciatic nerve stimulation (pulse duration 0. cats (14 animals) under chloralose anesthesia and myorelaxation. Electrostimulation was applied to motor zones of the cortex and the EMG-equivalent of the femoral muscle motor reaction was recorded. Conditioning stimulations were applied to the spongy substance of the ilium by means of two needle electrodes insulated their entire length except for the ends, introduced into the spongy bone at a depth of 3-4 mm and 3-4 mm apart (pulse duration 0.3 msec, strength 3-10 xmA). Experiments were performed using stereotaxis with Multibasis multipurpose neurophysiological apparatus (Biomedica) for 10 signal presentations. The amplitude fluctuations of the summated phases (from peak to peak) were subjected to statistical processing: 1-2 EP phases and deviations from the EMG response.The strength of sciatic nerve stimulation was selected at the level of threshold intensity sufficient for forming stable responses. For the sake of convenience the alterations of the indexes obtained for conditioning stimulations of the spongy substance of the ilium were estimated in percentages, taking the initial data as 100%. The interval between conditioning and test stimuli ranged from 100 to 1000 msec. RESULTSConditioning stimulations of the spongy substance of the ilium markedly affected the amplitude of the test EP and of the EMG response. For example, within the interval from 300 to 700 msec the summated

Spinal nociceptive transmission by mechanical stimulation of bone marrow

“…Previous studies have shown that both electrical stimulation and increase in pressure within bone marrow generate a blood pressure increase that may be indicative of nociceptive activation. 22 An increase in intraosseous pressure has been shown to activate fine-diameter afferent nerve fibers arising from bone marrow, as do irritant and inflammatory agents such as H + and K + ions and histamine and bradykinin. 23 These findings suggest that intraosseous nociceptors are activated by various kinds of stimuli including an increase in intraosseous pressure.…”