Stereometric characteristics of ultrastructure of presynaptic terminals in the dorsal horn of the cat spinal cord

Morphometric statistical techniques were used to investigate geometric aspects of 240 axodendritic presynaptic terminals (PT) located in the dorsal horn of the gray matter of the cat spinal cord. Parameters describing the configuration and average spatial radius of the three-dimensional PT (approximated by irregular ellipsoid were estimated on the basis of the morphometry of random PT sections applying aspects of the theory of probability. Lack of any correlation between location of the active zone and the configurational pattern (extent) of terminals was demonstrated. Densitometric distribution of average spatial PT radii was obtained (mean: 0.820 µm). The relatively limited scatter of this distribution would indicate extremely close similarity between parameters of the PT comprising the test group.Dnepropetrovsk University. A. A. Bogomolets Institute of Physiology, Academy of the Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 403–410, May–June, 1989.     

Numerical characteristics of synaptic vesicular apparatus structure in the dorsal horn of the cat spinal cord

Statistical parameters characterizing the structure of the vesicular apparatus of presynaptic endings (PE) were determined from the findings of ultrastructural morphometric analysis of 135 synapses in the dorsal horn of the cat spinal cord. Quantitative estimates of vesicles in the PE (averaging about 470) were obtained, based on stereometric principles. The bimodal pattern of distribution of distances from the center of each vesicle to the nearest portion of the active zone was demonstrated — viewed as the structural correlate of the two-pool model of transmitter storage. The possibility of classifying PE according to the sign of vesicle spatial distribution is discussed as well as the relationship between this distribution and parameters of transmitter mobilization and synaptic release.Dnepropetrovsk State University. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 5, pp. 597–605, September–October, 1989.     

Projections of afferent ventral root fibers on dorsal horn neurons in the cat spinal cord

Mechanisms of the effect of stimulation of afferent fibers in ventral roots on dorsal horn interneurons were investigated in experiments on anesthetized cats. Dorsal horn interneurons on which such fibers project were shown to exist. In particular, some dorsal horn interneurons can exert an inhibitory influence on effects of dorsal root fiber activation.Institute of Physiology, Academy of Sciences of the Kazakh SSR, Alma-Ata. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 300–305, May–June, 1985.     

Viscerosomatic somatic convergence at lumbar interneurons in the dorsal horn of the cat and rat spinal cord

In experiments on spinal cats, when branches of the pelvic nerve innervating the rectum were electrically stimulated at the same time as the peroneal nerve it was found that 12 out of 20 neurons, to which the effects of both these supplies converged, were activated by both A- and C-fibers. Responses to stimulation of the pelvic nerve were apparently mediated via fibers with a conduction velocity not less than 2.2 m·s^–1. In studies in spinal rats it was shown that distension of the more distal regions of the large intestine could excite neurons in laminae IV–V, and inhibit neurons in deeper laminae. In seven out of 18 cases the inhibition evoked by visceral stimulation was due to a direct effect on the postsynaptic membrane of these cells, and in 11 cases it was localized to presynaptic structures. Naloxone, strychnine, and atropine did not block this inhibition, thus providing evidence against the possible participation of opioids, glycine, and acetylcholine in its generation. Phaclofen, a GABA_B-receptor antagonist, was also without effect, but bicuculline suppressed this inhibition in three out of 12 cases, indicating that GABA_A-receptors are involved.I. M. Sechenov Medical Academy, Russian Ministry of Public Health, Moscow. Translated from Neirofiziologiya, Vol. 24, No. 1, pp. 3–11, January–February, 1992.     

Normal anatomy and physiology of the spinal cord dorsal horn

The dorsal horn of the spinal cord receives afferent input from innocuous primary afferent neurons via collaterals from the dorsal columns. This input is integrated and relayed primarily by neurons in laminae III-VI. Dorsal horn neurons which encode innocuous inputs project to the medulla and the cervical spinal cord via the dorsal columns and the dorsolateral funiculus. Nociceptive primary afferent neurons enter the spinal dorsal horn via collaterals from Lissauer's tract. Nociceptive input is integrated and relayed by neurons in laminae I, II and V which project to the reticular formation and thalamus via the anterolateral tract.     

Fractalkine and minocycline alter neuronal activity in the spinal cord dorsal horn

Fractalkine (FKN) evokes nociceptive behavior in nai ve rats, whereas minocycline attenuates pain acutely after neuronal injury. We show that, in nai ve rats, FKN causes hyperresponsiveness of lumbar wide dynamic range neurons to brush, pressure and pinch applied to the hindpaw. One day after spinal nerve ligation (SNL), minocycline attenuates after-discharge and responses to brush and pressure. In contrast, minocycline does not alter evoked neuronal responses 10 days after SNL or sciatic constriction, but increases spontaneous discharge. We speculate that microglia rapidly alter sensory neuronal activity in nai ve and neuropathic rats acutely, but not chronically, after injury.     

Ultrastructure of orexin-1 receptor immunoreactivities in the spinal cord dorsal horn

The ultrastructural properties of orexin 1-receptor-like immunoreactive (OX1R-LI) neurons in the dorsal horn of the rat spinal cord were examined using light and electron microscopy techniques. At the light microscopy level, the most heavily immunostained OX1R-LI neurons were found in the ventral horn of the spinal cord, while some immunostained profiles, including nerve fibers and small neurons, were also found in the dorsal horn. At the electron microscopy level, OX1R-LI perikarya were identified containing numerous dense-cored vesicles which were more heavily immunostained than any other organelles. Similar vesicles were also found within the axon terminals of the OX1R-LI neurons. The perikarya and dendrites of some of the OX1R-LI neurons could be seen receiving synapses from immunonegative axon terminals. These synapses were found mostly asymmetric in shape. Occasionally, some OX1R-LI axon terminals were found making synapses on dendrites that were OX1R-LI in some cases and immunonegative in others. The synapses made by OX1R-LI axon terminals were found both asymmetric and symmetric in appearance. The results provide solid morphological evidence that OX1R is transported in the dense-cored vesicles from the perikarya to axon terminals and that OX1R-LI neurons in the dorsal horn of the spinal cord have complex synaptic relationships both with other OX1R-LI neurons as well as other neuron types.     

Experimental morphological study of primary afferent terminals at the base of the dorsal horn of the cat spinal cord

The distribution and ultrastructure of primary afferent terminals in the gray matter of the cervical and lumbar regions of the cat spinal cord were studied by the experimental degeneration method of Fink and Heimer. Most preterminals of primary afferents were shown to be concentrated in the region of the intermediate nucleus of Cajal (central part of Rexed's laminae VI–VII), in the substantial gelatinosa (laminae II–III), and in the nucleus proprius of the dorsal horn (central and medial parts of lamina IV). Fewer are found in the region of the motor nuclei. The number of degenerating axon terminals in the lateral parts of laminae IV and V differed: 31.5 and 0.4% respectively of all axon terminals. Many terminals of primary afferents in lamina IV contribute to the formation of glomerular structures in which they exist as terminals of S-type forming axo-axonal connections with other terminals. These results are in agreement with electrophysiological data to show that interneurons in different parts of the base of the dorsal horn differ significantly in the relative numbers of synaptic inputs formed by peripheral afferents and descending systems.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 406–414, July–August, 1973.     

An interaction of opioids and galanin in dorsal horn of the spinal cord in mononeuropathic rats

The present study was performed in rats with experimentally induced mononeuropathy after common sciatic nerve ligation. The hind-paw withdrawal latencies to thermal and mechanical stimulation were increased significantly after intrathecal injection of 3 nmol of galanin. The increased hind-paw response latencies induced by galanin were attenuated by following intrathecal injection of 22 nmol, but not 11 or 2.75 nmol of the opioid receptor antagonist naloxone. Further, the increased hind-paw response latencies induced by galanin were prevented by following intrathecal injection of 10 nmol of mu-opioid receptor antagonist, beta-funaltrexamine (beta-FNA), but not by 10 nmol of delta-opioid receptor antagonist, natrindole or 10 nmol of kappa-opioid receptor antagonist, nor-binaltorphimine (nor-BNI). Intrathecal 10 nmol of beta-FNA alone had no significant effects on the hind-paw withdrawal responses. These results demonstrate the existence of a specific interaction between galanin and opioids in the transmission of presumed nociceptive information in the spinal cord of mononeuropathic rats. This interaction involves the activation of mu-opioid receptor.     

P2X receptor-mediated purinergic sensory pathways to the spinal cord dorsal horn

P2X receptors are expressed on different functional groups of primary afferent fibers. P2X receptor-mediated sensory inputs can be either innocuous or nociceptive, depending on which dorsal horn regions receive these inputs. We provide a brief review of P2X receptor-mediated purinergic sensory pathways to different regions in the dorsal horn. These P2X purinergic pathways are identified in normal animals, which provides insights into their physiological functions. Future studies on P2X purinergic pathways in animal models of pathological conditions may provide insights on how P2X receptors play a role in pathological pain states.     

Changes in the efficacy of transmission at synapses of the dorsal horn of the cat spinal cord observed during repetitive activation of cutaneous afferents

Inhibitory patterns in monosynaptic components of field potentials and potentials in the dorsal spinal cord surface were investigated during acute experiments on cats involving low-frequency stimulation of cutaneous peripheral nerves. Approximation of experimental data obtained from a theoretical plot was performed adopting a standard model of transmitter storage and release. Parameters of fractional release and replenishment of transmitter depleted from synaptic junctions were determined. Processes of replenishing supplies of transmitter for release were seen to intensify under rhythmic stimulation. A comparison between these experimental findings on the character of synapses of the monosynaptic reflex arc and others found in the literature indicated a similarity between the parameters of the mechanism underlying transmitter mobilization and release at different synaptic junctions formed by primary afferent fibers.Dnepropetrovsk State University Commemorating the 300th Aniversary of Ukraine-Russian Reunion, Dnepropetrovsk. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 491–497, July–August, 1987.     

Estimation of spatio-morphofunctional characteristics of presynaptic terminals in the lateral zone at the base of the dorsal horn

This article further develops a statistical/stereological model for estimating 3-dimensional population characteristics of cell elements based on analysis of random (2-dimensional) cross section of planes. This model was used to conduct morphometric electron microscope research on presynaptic terminals (PT) at lateral sites at the base of the dorsal horn of the cat spinal cord. Estimated distributions of PT volumes were thus found, as well as areas of PT axolemma with "corrugation" size of synaptic zones (AZ), and estimates of mean numbers of AZ on a 3-dimensional PT and statistical parameters of AZ location in relation to the point at which the axon passes into the synaptic bouton.Dnepropetrovsk State University. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 803–811, November–December, 1990.     

去甲肾上腺素在脊髓背角的镇痛机制

疹髓背角浅层是传递和调制外周伤害性信息的关键部位。起源于脑干的去甲肾上腺素（NA）能纤维终止脊髓背角,它们释放的NA具有抑制初级传入末梢释放谷氨酸和P物质、增加Ⅱ层（胶状质）抑制性神经活性物质释放的作用。此外,形态学研究提示NA可能直接抑制Ⅰ/Ⅲ层向丘脑传递伤害性信息的投射神经元。NA可能通过以上途径,实现对外周伤害性信息传递的调制而发挥镇痛作用。     

MK-801抑制福尔马林实验引起的大鼠脊髓背角环氧合酶-2的表达

应用免疫组织化学方法,观察鞘内注射N-methyl—D—aspartate(NMDA)受体拮抗剂MK-801对福尔马林实验引起的大鼠脊髓背角环氧合酶-2(cyclooxygenase-2,COX-2)表达的影响。结果表明：MK-801对福尔马林实验引起的第1相缩足反射仅有一定抑制作用,但对第2相缩足反射有显著的抑制作用,且呈剂量依赖性。与这种行为学的变化相对应,MK-801可显著抑制福尔马林实验引起的脊髓背角COX-2表达的增加,并且这种抑制作用与MK-801的剂量呈正相关。这些结果表明,在福尔马林实验中,NMDA受体的活动是引起脊髓背角COX-2表达增加的原因之一。     

Effects of clopheline on impulse activity of neurons in the midbrain and dorsal horn of the spinal cord

Clophelin (1-5 mg/kg) suppresses spinal dorsal horn neuronal nociceptive responses but does not change their touch stimuli reactions in unanesthetized curarized cats. This effect is steady to naloxone (1 mg/kg), yohimbine (5 mg/kg) and removal by prazosin (1 mg/kg). Clophelin depresses nociceptive responses of the central gray matter neurones which generalized pain impulses in the supraspinal structures.