[Entry pathways of painful afferent pathways into the spinal cord].
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Afferent Pathways↗
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[Effects of morphine on evoked potential recorded from pain-afferent pathways (author's transl)].
Effects of morphine (1 mg/kg i.v.) were examined on evoked potential of somatosensory afferent pathways elicited by tooth pulp stimulation in cats. Results were as follows: In central gray (CG) of the midbrain which has a triphasic evoked potential with a short latency, morphine decreased the amplitude. In nucl. lateralis posterior(LP) and nucl. medialis dorsalis(MD) of the thalamus, association relay nuclei, which have a late component followed by a fast component with a relatively short latency, morphine decreased the amplitude of the late component but not that of fast component of the evoked potential. In nucl. centralis lateralis(CL) of the thalamus, intralaminar nuclei, and pre-central association area(PCA) of the cortex, which have monophasic and triphasic evoked potentials with a long latency, respectively, morphine markedly decreased the amplitude of both evoked potentials. In nucl. ventralis posteromedialis(VPM) and somatic sensory area I (SI), lemniscal system, which has biphasic and mutiphasic evoked potentials with a short latency, respectively, morphine had no effect on these evoked potentials. As these depressant effects of morphine on evoked potentials were antagonized by naloxone (0.2mg/kg i.v.), a specific morphine action is suggested.
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The negative potential wave evoked in cuneate nucleus by stimulation of afferent pathways: its origins and susceptibility to inhibition.
1. The negative (N)-wave evoked at various depths in the cuneate nucleus by stimulation of afferents in the ipsilateral forepaw or dorsal column has been studied in the rat. 2. Micro-iontophoretic applications of gamma-aminobutyric acid (GABA) into the vicinity of the recording electrode markedly reduced the amplitude of the negative wave, but only when recordings were made near the base of the cuneate nucleus. Nearer the surface of the medulla, GABA was much less effective. 3. A similar depth distribution obtained for the depression of the negative wave by micro-iontophoretic Mg2+ and enhancement by Ca2+. 4. Depression of the negative wave by conditioning stimulation of the afferent pathway also showed a similar depth distribution. The conditioned depression of the negative wave was most marked during the first 30 ms after the conditioning stimulus and this early depression could be antagonized by iontophoretic (+)-bicuculline methochloride. A lesser degree of conditioned inhibition of the negative wave persisted up to 80-200 ms but this was resistant to (+)-bicuculline methochloride. Thus, conditioned depression of the negative wave appeared to be mediated only in part by a GABA-like transmitter. 5. It is concluded that the negative wave recorded near the base of the cuneate nucleus has some of the predicted properties of a post-synaptic potential. These properties are not seen when the negative wave is recorded more superficially, near the surface of the medulla.
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[Sources of the afferent pathways of the motor cortex in cats revealed by using the peroxidase method].
By means of the method based on the retrograde axonal transport of exogenic horse-radish peroxidase, there have been stated the sources of afferent pathways of the motor cortex and the structure of neurons sending their axons to the given region. The marked neurons have been found in ipsilateral (SI, SII, Pr, Limb.) and contralateral cortex (MI, Limb.), as well as in the diencephalon (LP, VPL, Hp), the mesencephalon (NR, SN, TM) and the pons (TP). The complex investigation (the peroxidase method and electron microscopy) allowed to get an idea on morphological substrate of disynaptic pathways.
Animals↗
[Analgesic effect of pentazocine and its action on nociceptive afferent pathway].
Nociceptive stimulus was applied to the skin of adult cats by pinching with a serrated forceps or by radiant heat with Pain meter. This stimulation caused motor or emotional responses such as movements of the head and trunk, vocalization, escape and attack. After the administration of pentazocine, these responses disappeared and the animals behaved normally. Analgesic action appeared approximately 15 min after the administration and lasted more than 90 min. Effects of pentazocine on pain-afferent pathways were studied and the evoked potential was recorded by tibial nerve stimulation. Though pentazocine did not influence the evoked potential recorded from somatic sensory area I and mesencephalic central gray, the evoked potential in pre-central association area, nucleus centralis lateralis, nucleus suprageniculatus-limitans and reticularis pontis caudalis was reduced by pentazocine.
Afferent Pathways↗
The rubro-bulbospinal path. A descending system known to influence dynamic fusimotor neurones and its interaction with distal cutaneous afferents in the control of flexor reflex afferent pathways.
The inhibitory effect of electrical stimulation in the near-rubral region on polysynaptic segmental as well as ascending pathways activated by the flexor reflex afferents (FRA) in hind limb nerves was studied in chloralose anaesthetized cats. The effective stimulating region totally coincided with the one from which a D zone climbing fibre response may be elicited in the contralateral cerebellar cortex. The descending path was dependent upon an intact dorsolateral spinal funiculus, where also a characteristic volley could be recorded with a surface electrode on short train central stimulation. The suppressive action on the transmission through the FRA pathways was evoked in the absence of a lower lumbar dorsal root potential, and it was concluded that the effect was exerted by postsynaptic inhibition. It was suggested that this descending path, the effects of which resemble those elicited from the dorsal reticulospinal system, is identical to the rubro-bulbospinal path, previously known to influence dynamic fusimotor neurones. The transmission through the FRA pathways was also suppressed by conditioning stimulation of ipsilateral, low threshold distal cutaneous afferents. The time course of this effect was the same as that with central conditioning stimulation. Facilitatory interaction was revealed with double conditioning and it was suggested that the descending path and the distal cutaneous afferents converge upon a common group of interneurones, which postsynaptically inhibit an early (possibly the first one) interneurone in the FRA pathways. As low threshold distal cutaneous afferents supply the primary peripheral input via climbing fibres to the cerebello-cortical D zone, it was concluded that the different stimuli (central or peripheral) which activate a common group of inferior olivary neurones destined for the D zone also activate a common group of segmental inhibitory interneurones. The results are discussed in relation to current concepts of segmental motor control, and it is suggested that the mechanisms studied could be involved in the regulation of stepping.
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Inhibitory actions from low and high threshold cutaneous afferents on groups II and III muscle afferent pathways in the spinal cat.
The inhibitory effects caused by volleys in cutaneous afferents on the transmission through some polysynaptic segmental pathways activated by high threshold muscle afferents were studied in chloralose anesthetized, spinal cats. Pathways studied were groups II and III to motoneurones as well as group II to primary afferents. The results suggested that two different mechanisms were involved. One mechanism, with a very slow time course (duration more than 400 ms), is suggested to be an example of presynaptic inhibition between different primary afferent systems. This mechanism required high threshold (greater than or equal to 1.6T) conditioning shocks, and appeared simultaneously with the component II dorsal root potential being evoked by the cutaneous afferent volley. The other mechanism, with a faster time course (duration always below 300 ms), was dependent upon low threshold (less than or equal to 1.5T) cutaneous conditioning volleys. This inhibitory interaction could not be ascribed to the same presynaptic mechanism, but is suggested to be an example of postsynaptic inhibition at an interneuronal level. The presumed disynaptic excitatory pathway from group II muscle afferents to flexor motoneurones was not inhibited by cutaneous conditioning shocks, but could on the contrary be facilitated by activity in low threshold cutaneous afferents, probably at the only interneurone involved in this group II pathway.
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Afferent pathways of the blink reflex.
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Afferent Pathways↗
[The role of vestibular and proprioceptive afferent pathways in the reaction to pushing (author's transl)].
The reaction to pushing was studied in 6 normal subjects and 3 patients with bilateral peripheral vestibular lesions. The reaction to pushing was tested on the anterior tibial and soleus, by modifying the proprioceptive afferent impulses. The respective parts of the vestibular, proprioceptive, visual components, and of a sudden, start are analyzed; the afferent impulses obtain information from the initial posture and modulate the relative importance of these different factors at a supra-segmentary level.
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Contributions of different afferent pathways to the catecholamine and 5-hydroxytryptamine-innervation of the amygdala: a neurochemical and histochemical study.
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Afferent Pathways↗
[Restoration of instrumental movements in cats after section of spinal cord afferent pathways].
Instrumental fore-leg movements (pedal pressing) were studied in the course of recovery of motor functions after section of the posterior columns and the spino-cervical tract at the cervical level. Recovery of supporting-locomotor functions reached a high level. Instrumental reactions connected with inborn forms of motor activity (running etc.) were being restored parallel to the locomotion restoration. Complex instrumental movements were restored slower and didn't reach a high degree of accuracy. A more simple instrumental movement (pressing on the open pedal) had a more rapid and more complete recovery. It is concluded that the possibilities of substitution of different channels, transmitting afferent somatic impulses to the sensorimotor cortex, are very limited for elaborated instrumental movements.
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[Effect of narcotic analgesics on the cortical control process of impulse transmission in the afferent pathways of the sciatic nerve].
The effect produced by narcotic analgetics with their intravenous administration on the process of cortical control over the transmission of impulses along specific routes of the sciatic nerve was studied. The conditioning stimulation of the cortex was effected by using a monopolar electrode through single electric impulses. The interval between conditioning and test (on sciatic nerve) impulses was of 80-120 ms. Morphine (1-2 mg/kg), promedol (trimeperidin) (1-2 mg/kg) and phentanyl (100 gamma/kg) potentiated the inhibition of evoked potentials in the nucleus gracilis and in VPL, observed upon stimulation of the cortex of optic lobuses. The intensification of inhibitory corticifugal mechanisms occurring under the effect of narcotic analgetics takes place both on the level of the medulla oblongata and of the thalamic one.
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The seventh cranial nerve of the rat. Visualization of efferent and afferent pathways by cobalt precipitation.
The cobalt sulphide precipitation technique, in conjunction with Timm's intensification procedure, was used to delineate the afferent and efferent intramedullary pathways of the seventh cranial nerve complex in the rat. The branchial motor nucleus with the accompanying first part, genu, and second part of the root are described. The motor branches to the superficial facial musculature do not contain fibres of geniculate ganglion origin or fibres which terminate in the spinal trigeminal nucleus. The motor branches to the deep facial muscles arise from the dorsal part of the branchial motor nucleus and traverse to the midline medial to the genu, then project under the genu into the lateral reticular formation before exiting with the facial nerve. The salivatory and lacrimal nuclei and their intramedullary pathways are described. Sensory fibres from the cutaneous auricular branch enter the spinal trigeminal tract and most of the chorda tympani gustatory fibres enter the fasciculus solitarius. A smaller number of gustatory fibres extend medially to the region of the salivatory nucleus. Fibres of greater superficial petrosal origin also enter the fasciculus solitarius as well as the medial reticular formation. These findings are discussed in relation to previous anatomical, physiological and clinical reports.
Animals↗
[Afferent pathway from locus coeruleus to the nucleus solitarius].
After the destruction of the nucleus tractas solitarii, just caudally to the writing pen by means of a stereotaxic instrument, the system of afferent fibres to the nucleus in question was investigated by the methods of Nauta and Fink--Heimer. The fibre terminals were revealed near locus coeruleus. Investigation of the locus coeruleus by Golgi method demonstrated that it usually has neurons of reticular type and transitional ones which resemble by their form the neurons specific for sensory formations. It is possible to conclude that locus coeruleus posesses connections of visceral origin which may play a part in the afferent influence of locus coeruleus on the brain cortex.
Animals↗
[Electrical reactions in the afferent pathways of the small intestine of wakeful dogs during feeding and during the process of digestion].
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Animals↗
[Effect of narcotic analgesics on impulse conduction along the afferent pathways of visceral nerves].
Experiments were conducted on chloralose-anesthetized cats. The action of morphine and promedol upon the potentials of the cortical and subcortical structures occurring after the visceral nerve stimulation was studied. Morphine proved to depress the potentials evoked by stimulation of the inferior cardiac and vagus nerves, in the specific, associative and nonspecific structures of the brain; promedol produced an analogous effect. Morphine also inhibited the potentials occurring after the stimulation of the splanchnic nerve in the associative and nonspecific structures; depression of the responses in the specific pathways was less pronounced.
Animals↗
The vasomotor centre and its afferent pathways.
1. Experiments were carried out on two groups of anaesthetized greyhounds. The response of the first group to infusions of angiotensin II into a vertebral artery for 5 min and to bilateral occlusion of the common carotid arteries for 2 min was studied before and after bilateral ablation of the areas postrema. The response of the second group to infusions of angiotensin and to carotid occlusion was studied before and after mid-collicular transection of the midbrain. 2. Bilateral ablation of the areas postrema abolished the response to angiotensin infused into a vertebral artery at the dose used but did not significantly alter the response to carotid occlusion. Transection of the midbrain did not abolish the response to either procedure. 3. It is concluded that the structures involved in the cardiovascular response to carotid occlusion are anatomically distinct from the area postrema and that neither response requires the integrity of connections above the pons. 4. An attempt has been made to construct a schematic diagram of the vasomotor centre.
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[Effect of narcotics on impulse conduction in the afferent pathways of visceral nerves].
In tests set up on cats immobilized with pyraxolone and anatruxonium the effect of non-inhalation narcotics on the evoked potentials of the cortex and subcortical structures with visceral and also somatic, acoustic and photo-stimulation was studied. With stimuli of different modality sodium ethaminal was found to inhibit evoked potentials of the cerebral hemispheres, diencephalon and midbrain cortex. Hexabarbital sodium suppressed biopotentials in specific, associative and non- specific brain structures in the event of visceral and somatic stimulation. Viadril enhanced the amplitude of potentials in all types of stimulation Urethan inhibited potentials in specific pathways of visceral and somatic nerves as well as in associative and non-specific brain structures following visceral, somatic and acoustic stimulation, with the amplitude of potentials to photostimulation then increasing.
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