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Journal of Smooth Muscle Research =... Jun 2005The micturition reflex is one of the autonomic reflexes, but the release of urine is regulated by voluntary neural mechanisms that involve centers in the brain and... (Review)
Review
The micturition reflex is one of the autonomic reflexes, but the release of urine is regulated by voluntary neural mechanisms that involve centers in the brain and spinal cord. The micturition reflex is a bladder-to-bladder contraction reflex for which the reflex center is located in the rostral pontine tegmentum (pontine micturition center: PMC). There are two afferent pathways from the bladder to the brain. One is the dorsal system and the other is the spinothalamic tract. Afferents to the PMC ascend in the spinotegmental tract, which run through the lateral funiculus of the spinal cord. The efferent pathway from the PMC also runs through the lateral funiculus of the spinal cord to inhibit the thoracolumbar sympathetic nucleus and the sacral pudendal nerve nucleus, while promoting the activity of the sacral parasymapathetic nucleus. Inhibition of the sympathetic nucleus and pudendal nerve nucleus induces relaxation of the bladder neck and the external urethral sphincter, respectively. There are two centers that inhibit micturition in the pons, which are the pontine urine storage center and the rostral pontine reticular formation. In the lumbosacral cord, excitatory glutamatergic and inhibitory glycinergic/GABAergic neurons influence both the afferent and efferent limbs of the micturition reflex. The activity of these neurons is affected by the pontine activity. There are various excitatory and inhibitory areas co-existing in the brain, but the brain has an overall inhibitory effect on micturition, and thus maintains continence. For micturition to occur, the cerebrum must abate its inhibitory influence on the PMC.
Topics: Animals; Central Nervous System; Humans; Urinary Bladder; Urination; Urine
PubMed: 16006745
DOI: 10.1540/jsmr.41.117 -
Urologia Internationalis 1999Bladder sensation is transmitted both via the spinothalamic tract in the lateral funiculus and the dorsal system in the dorsal funiculus. We transected the dorsal...
Bladder sensation is transmitted both via the spinothalamic tract in the lateral funiculus and the dorsal system in the dorsal funiculus. We transected the dorsal funiculus in 10 female cats to clarify the functional roles of these two ascending pathways. The dorsal funiculus was transected at T10 in 5 decerebrate and 5 freely-moving cats, and micturition parameters were compared before and after transection. Transection of the dorsal funiculus did not affect any of the parameters of reflex micturition in the 5 decerebrate cats. Within 1 week after transection, 4 of the 5 freely-moving cats used the normal micturition posture, but the remaining one performed micturition in a prone position as if she had lost micturition sensation. All 5 cats urinated with a normal micturition posture by 2 weeks after transection. The mean single voided volume was decreased transiently up to 1 week, but returned to normal by 2 weeks after transection. None of the 5 cats had any residual urine before and after transection. Both the ascending and descending limbs of the micturition reflex pass through the lateral funiculus. Bladder sensation is transmitted both via the spinothalamic tract coursing in the lateral funiculus and the dorsal system in the dorsal funiculus. The dorsal system may play a major role in the transmission of bladder sensation to the cerebral cortex, but may not be essential.
Topics: Animals; Cats; Decerebrate State; Female; Reflex; Spinal Cord Injuries; Spinothalamic Tracts; Thoracic Vertebrae; Urinary Bladder; Urination
PubMed: 10738190
DOI: 10.1159/000030443 -
Temperature (Austin, Tex.) 2023Thermoregulatory behaviors are powerful effectors for core body temperature (T) regulation. We evaluated the involvement of afferent fibers ascending through the dorsal...
Selection of preferred thermal environment and cold-avoidance responses in rats rely on signals transduced by the dorsal portion of the lateral funiculus of the spinal cord.
Thermoregulatory behaviors are powerful effectors for core body temperature (T) regulation. We evaluated the involvement of afferent fibers ascending through the dorsal portion of the lateral funiculus (DLF) of the spinal cord in "spontaneous" thermal preference and thermoregulatory behaviors induced by thermal and pharmacological stimuli in a thermogradient apparatus. In adult Wistar rats, the DLF was surgically severed at the first cervical vertebra bilaterally. The functional effectiveness of funiculotomy was verified by the increased latency of tail-flick responses to noxious cold (-18°C) and heat (50°C). In the thermogradient apparatus, funiculotomized rats showed a higher variability of their preferred ambient temperature (T) and, consequently, increased T fluctuations, as compared to sham-operated rats. The cold-avoidance (warmth-seeking) response to moderate cold (whole-body exposure to ~17°C) or epidermal menthol (an agonist of the cold-sensitive TRPM8 channel) was attenuated in funiculotomized rats, as compared to sham-operated rats, and so was the T (hyperthermic) response to menthol. In contrast, the warmth-avoidance (cold-seeking) and T responses of funiculotomized rats to mild heat (exposure to ~28°C) or intravenous RN-1747 (an agonist of the warmth-sensitive TRPV4; 100 μg/kg) were unaffected. We conclude that DLF-mediated signals contribute to driving spontaneous thermal preference, and that attenuation of these signals is associated with decreased precision of T regulation. We further conclude that thermally and pharmacologically induced changes in thermal preference rely on neural, presumably afferent, signals that travel in the spinal cord within the DLF. Signals conveyed by the DLF are important for cold-avoidance behaviors but make little contribution to heat-avoidance responses.
PubMed: 37187830
DOI: 10.1080/23328940.2023.2191378 -
Der Radiologe Mar 2021Spinal cord injuries are frequently associated with severe clinical-neurological deficits. These are evident with specific symptoms and syndromes. Hereby, a thorough... (Review)
Review
BACKGROUND
Spinal cord injuries are frequently associated with severe clinical-neurological deficits. These are evident with specific symptoms and syndromes. Hereby, a thorough knowledge of spinal neuroanatomy is essential.
METHODS
Spinal anatomy, examination procedures and classical spinal syndromes are presented.
RESULTS
Important spinal syndromes comprise the dorsal cord syndrome, spinothalamic tract syndrome, pyramidal tract syndrome, central cord syndrome, transversal and Brown-Séquard syndrome as well as combined syndromes.
CONCLUSION
Clinical examination allows assessment and anatomical classification of spinal syndromes and targeted examination of the spinal cord using additional diagnostic methods.
Topics: Brown-Sequard Syndrome; Humans; Spinal Cord; Spinal Cord Injuries; Spine
PubMed: 33590288
DOI: 10.1007/s00117-021-00817-3 -
Neuroscience Dec 2013In this review we discuss recent advances in the understanding of the development of forebrain projections attending to their origin, fate determination, and axon... (Review)
Review
In this review we discuss recent advances in the understanding of the development of forebrain projections attending to their origin, fate determination, and axon guidance. Major forebrain connections include callosal, corticospinal, corticothalamic and thalamocortical projections. Although distinct transcriptional programs specify these subpopulations of projecting neurons, the mechanisms involved in their axonal development are similar. Guidance by short- and long-range molecular cues, interaction with intermediate target populations and activity-dependent mechanisms contribute to their development. Moreover, some of these connections interact with each other showing that the development of these axonal tracts is a well-orchestrated event. Finally, we will recapitulate recent discoveries that challenge the field of neural wiring that show that these forebrain connections can be changed once formed. The field of reprogramming has arrived to postmitotic cortical neurons and has showed us that forebrain connectivity is not immutable and might be changed by manipulations in the transcriptional program of matured cells.
Topics: Animals; Axons; Cerebral Cortex; Humans; Nerve Net; Prosencephalon
PubMed: 24042037
DOI: 10.1016/j.neuroscience.2013.08.070 -
Neurochemical Pathology Dec 1986The frog dorsal root provides a useful model for the study of axonal regeneration in an adult vertebrate CNS. We have used the model to compare the regeneration of two... (Review)
Review
The frog dorsal root provides a useful model for the study of axonal regeneration in an adult vertebrate CNS. We have used the model to compare the regeneration of two very different types of axons within the same CNS environment and have found that regenerating dorsal root, as well as rerouted motoneuron axons, display similar growth patterns in the spinal cord. Both sensory and motor axons grow preferentially in some regions and not in others. They both regenerate effectively longitudinally as well as radially within the dorsolateral fasciculus (DLF). By contrast, fewer sensory and motor axons regenerate longitudinally or radially in the dorsal funiculus (DF). This similar preferential growth of two very different populations of axons suggests that the growth patterns reflect regional differences in the cellular environment of the cord. The DLF has fascicles of unmyelinated axons separated by radial glial processes and, after dorsal root injury, is mildly gliotic. By contrast, DF has very large myelinated axons, which widely separate the radial glial processes that traverse the region. After dorsal root injury, this region is markedly gliotic and contains myelin, debris and oligodendroglia, and microglial macrophages. Our data suggest that unmyelinated axons and radial glial processes are more preferred substrates for axonal growth than myelin debris, oligodendroglia and macrophages. It is not surprising, then, that regions of the adult mammalian CNS that are characterized by large myelinated axons fail to support axonal growth. Moreover, there is some evidence that regions of the adult mammalian CNS that are characterized by unmyelinated axons support axonal growth.
Topics: Animals; Axons; Motor Neurons; Nerve Regeneration; Neuroglia; Neuronal Plasticity; Neurons, Afferent; Ranidae; Spinal Cord
PubMed: 3306473
DOI: 10.1007/BF02842938 -
Journal of Physiology, Paris 1999Presynaptic inhibition of primary afferents can be evoked from at least three sources in the adult animal: 1) by stimulation of several supraspinal structures; 2) by... (Review)
Review
Presynaptic inhibition of primary afferents can be evoked from at least three sources in the adult animal: 1) by stimulation of several supraspinal structures; 2) by spinal reflex action from sensory inputs; or 3) by the activity of spinal locomotor networks. The depolarisation in the intraspinal afferent terminals which is due, at least partly, to the activation of GABA(A) receptors may be large enough to reach firing threshold and evoke action potentials that are antidromically conducted into peripheral nerves. Little is known about the development of presynaptic inhibition and its supraspinal control during ontogeny. This article, reviewing recent experiments performed on the in vitro brainstem/spinal cord preparation of the neonatal rat, demonstrates that a similar organisation is present, to some extent, in the new-born rat. A spontaneous activity consisting of antidromic discharges can be recorded from lumbar dorsal roots. The discharges are generated by the underlying afferent terminal depolarizations reaching firing threshold. The number of antidromic action potentials increases significantly in saline solution with chloride concentration reduced to 50% of control. Bath application of the GABA(A) receptor antagonist, bicuculline (5-10 microM) blocks the antidromic discharges almost completely. Dorsal root discharges are therefore triggered by chloride-dependent GABA(A) receptor-mediated mechanisms; 1) activation of descending pathways by stimulation delivered to the ventral funiculus (VF) of the spinal cord at the C1 level; 2) activation of sensory inputs by stimulation of a neighbouring dorsal root; or 3) pharmacological activation of the central pattern generators for locomotion evokes antidromic discharges in dorsal roots. VF stimulation also inhibited the response to dorsal root stimulation. The time course of this inhibition overlapped with that of the dorsal root discharge suggesting that part of the inhibition of the monosynaptic reflex may be exerted at a presynaptic level. The existence of GABA(A) receptor-independent mechanisms and the roles of the antidromic discharges in the neonatal rat are discussed.
Topics: Animals; Animals, Newborn; Evoked Potentials; Neurons, Afferent; Rats; Spinal Nerve Roots; gamma-Aminobutyric Acid
PubMed: 10574124
DOI: 10.1016/s0928-4257(00)80063-7 -
Experimental Brain Research Jul 1975In adult cats the successive degeneration technique has been used to demonstrate the existence and distribution pattern of lateral funicular fibers to the dorsal column...
In adult cats the successive degeneration technique has been used to demonstrate the existence and distribution pattern of lateral funicular fibers to the dorsal column nuclei (DCN) originating from the brachial and thoracic cord. In a first operation, interruption of the dorsal columns at appropriate cervical levels and of the lateral funiculus at low thoractic levels was performed. Thirteen months later, a lesion was made in the lateral funiculus at upper brachial or uppermost thoracic levels. Fiber degeneration in the DCN consequent to this second operation is not contaminated by damage to dorsal roots or by interruption of lateral funicular afferents from lumbo-sacro-coccygeal segments. All animals were sacrificed 7 days after the second operation. Serial sections through the medulla oblongata, impregnated with the Fink-Heimer technique, show that fibers ascending from brachial levels in the dorsal part of the lateral funiculus reach the cuneate nucleus either by a dorsomedial route through the tegmentum or by cuneate nucleus either by a dorsomedial route through the tegmentum or by ascending in the restiform body. Degenerated fibers distribute selectively to the rostral part, and to a lesser extent to the base of the cuneate nucleus. Only very few fibers ascending from thoracic levels in the lateral funiculus distribute to the DCN. In another group of animals, not previously deafferented, a lesion of the lateral funiculus was made at upper brachial levels. This group served as a control to assess whether sprouting had occurred in the chronic preparations as a consequence of the long-term deafferentation. Comparison of the results in the cuneate nucleus of the two groups of animals shows no difference in the pattern of distribution or in the amount of degenerated fibers in this nucleus. These observations are discussed in relation to the question of collateral sprouting in the adult mammalian central nervous system.
Topics: Animals; Cats; Cervical Vertebrae; Lumbar Vertebrae; Medulla Oblongata; Nerve Degeneration; Spinal Cord; Spinal Nerve Roots; Thoracic Vertebrae; Time Factors
PubMed: 1149844
DOI: 10.1007/BF00238725 -
Experimental Brain Research 1968
Topics: Animals; Cats; Electric Stimulation; Electrophysiology; Hair; Muscles; Neural Conduction; Sensory Receptor Cells; Skin; Spinal Cord; Touch; Vibration
PubMed: 5712691
DOI: 10.1007/BF00235701