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PubMed1980

Reciprocal connections between substantia nigra and medullary reticular formation in the rat.

Electrophysiological analysis shows reciprocal connections between substantia nigra and medullary reticular formation (nucleus reticularis giganto celullaris). The nigro-reticular connection appears to be monosynaptic, as shown by antidromic activation, and comprises an ipsi and a contralateral component. Its effect is mainly inhibitory. The reticulonigral component produces mainly excitatory effects and includes fibres from nucleus giganto celullaris and nucleus parvocelullaris in the medullary reticular formation.

Afferent Pathways↗
PubMed1994

Modulation of gastric perception and motility in man. Current concepts and correlation with symptoms.

Gastric function is controlled by central and peripheral modulation. Most often, afferent information from the stomach does not reach conscious level. At extremes of chemical and mechanical stimulation, however, afferent signals are perceived as pain. Whether or not a signal is perceived depends on gating of afferent signals at the levels of both spinal cord and brainstem. Inhibition of gastric tone and peristalsis during perceived discomfort largely results from stimulation via sympathetic neural pathways. These findings may be clinically relevant because upper gastrointestinal symptoms in many dyspeptic patients could be the result of primary afferent neuron dysfunction rather than motor dysfunction.

Afferent Pathways↗
PubMed1997

Neurophysiology of micturition and continence in women.

Micturition and continence involve the coordination of complex neural events between the central and peripheral nervous systems. An understanding of these events provides a foundation for the treatment of voiding disorders in women such as stress urinary incontinence, urge incontinence and interstitial cystitis. The purpose of this paper is to comprehensively review the neuroanatomy, neurophysiology and neuropharmacology of micturition and continence. However, a brief section discussing clinical correlations will follow each of these topics to help integrate the basic science with clinical observations.

Afferent Pathways↗
PubMed2002

Cervical myofascial pain and headache.

Myofascial pain is a common cause of regional chronic pain. Myofascial trigger points can refer pain to the head and face in the cervical region, thus contributing to cervicogenic headache. When identified properly, cervical myofascial pain is a treatable component of headache management. This article reviews current literature on the pathophysiology, diagnosis, and management of cervical myofascial pain.

Afferent Pathways↗
PubMed1987

The afferent innervation of the thymus gland in the rat.

The afferent nervous supply to the thymus gland has been investigated by means of the retrograde transport of horseradish peroxidase. It has been shown that the thymus receives an afferent supply from the nodose ganglia of the vagus and from the dorsal root ganglia C1-C7. The afferent innervation of the right and left thymic lobes is bilaterally organized; the fibers of a small celled population of nodose ganglion neurons cross outside the thymus and those of a larger celled population cross within the thymus gland. The functional implications of these findings are discussed in the context of central nervous system-immune system interactions.

Afferent Pathways↗
PubMed1992

Electrophysiological evidence for reciprocal connectivity between the nucleus accumbens septi and ventral pallidal region.

Responses of nucleus accumbens (NAS) neurons to ventral pallidum (VP) stimulation were examined in anesthetized rats. Results demonstrated: (1) NAS to VP projection neurons reside primarily in the relatively lateral aspects of the NAS, and (2) substantial VP to NAS feedback also exists. These feedback projections are widely distributed throughout the NAS. Moreover, functionally identifiable NAS neuronal subpopulations were revealed by analysis of unit responses to concurrent VP and fimbria stimulation: (1) most, but not all NAS units responded to VP and fimbria stimulation in qualitatively divergent ways; (2) many NAS units demonstrated monosynaptic convergence of fimbria and VP terminations onto individual NAS units; and (3) in other cases, identified NAS-VP projection neurons were also monosynaptically activated by fimbria stimulation.

Action Potentials↗
PubMed1989

Comparison of vestibular and auditory startle responses in the rat and cat.

Cats, humans, and many other animals show stereotyped EMG responses in limb and axial muscles if suddenly dropped into free-fall. In cats, these free-fall responses (FFR) consist of highly synchronized bursts in most limb and axial muscles at 18-22 ms. We have used FFR to evaluate descending motor function and recovery in chronic spinal injured cats. Here FFR are compared with auditory evoked startle reflexes (ASR) in the hindlimb muscles of the rat and cat to determine whether they are related, and whether they could be used to evaluate descending motor function in the rat. ASR and FFR in the two species were similar except that the earliest components for both responses occurred around 9 ms in the rat versus 18-20 ms in the cat. Also, FFR in cats were usually more consistent and greater in amplitude during repeated drops than in rats, while the converse was true for ASR. Rat FFR amplitudes increased significantly after administering ketamine or 4-aminopyridine (4-AP), especially with both drugs together, while ASR amplitudes did not. FFR in cats recorded under ketamine analgesia were not normally improved by 4-AP. Finally, both FFR and ASR were suppressed by pentobarbital, chloralose, or motor activity. These data suggest that: (1) FFR appears to be a vestibular evoked startle reflex; (2) in the rat, ASR should be useful as a test of descending motor function following spinal injury, and (3) the combination of ketamine and 4-AP may be useful in revealing the presence of functional spinal pathways after CNS trauma.

4-Aminopyridine↗
PubMed1983

Development of the serotonergic system in the rat embryo: an immunocytochemical study.

The development of central serotonergic neurons has been examined immunocytochemically utilizing an antiserum to serotonin (5-HT). Cells of the B4-B9 complex are first detected early on embryonic day 13 (E13; 7 mm crown rump length, CRL) and increase rapidly in number through E15 when they appear as bilateral columns situated from just caudal to the mesencephalic flexure to the pontine flexure. Aggregation of cells into subgroups is apparent soon after 5-HT neurons leave the ventricular zone, allowing the identification of certain subdivisions of the B4-B9 complex long before they assume their adult locations. The initial detection of 5-HT immunoreactive cells in the medulla occurs 1-2 days after the appearance of cells in the B4-B9 complex, although it has been reported that the time of origin of medullary raphe neurons (B1-B3) occurs before that of raphe neurons in the midbrain and pons (B4-B9). The first medullary 5-HT neurons, comprising the B3 subdivision occur ventro-laterally on E14 (10-11 mm CRL) at least 1-2 days before midline 5-HT neurons are visualized in the B1 and B2 groups. Thus, in contrast to cells in the B4-B9 complex, medullary 5-HT neurons complete much of their migration before they can be detected immunocytochemically, indicating that the time of onset of transmitter synthesis and storage may differ during differentiation of cells sharing a common neurotransmitter phenotype. The formation of ascending 5-HT fiber projections occurs rapidly from cells of the B4-B9 complex. Within 24 hours after the initial detection of 5-HT fiber immunoreactivity in such cells at E13, their axons are seen entering the caudal diencephalon (E14). These fibers have traversed the diencephalon and floor of the telencephalon by E15-E16 and reach the frontal neocortical pole by E17. The main ascending bundle of 5-HT axons courses through the diencephalon in the vicinity of the medial forebrain bundle, although some fibers also diverge and travel along certain pre-existing non-5HT pathways. However, examples are also found of acute directional changes in 5-HT fiber growth which do not appear to be associated with pre-formed non-5HT pathways. The pattern of ascending fiber outgrowth suggests a priority routing system which provides certain regions with 5-HT axons in a preferential sequence irrespective of the distance of these areas from 5-HT cell groups or from major bundles of ascending 5-HT fibers.

Afferent Pathways↗
PubMed2005

Facilitation and inhibition of withdrawal reflexes following repetitive stimulation: electro- and psychophysiological evidence for activation of noxious inhibitory controls in humans.

A systematic evaluation of nociceptive withdrawal reflexes and pain rating was undertaken in order to explore the mechanisms underlying temporal summation of repetitive electrocutaneous stimulation in healthy individuals (n=12; age=27.5+/-1.5 years). Five-second subreflex threshold (RT) electrocutaneous stimulation at different frequencies (single stimulus, 5, 10, and 20 Hz) and intensities (0.6RT and 0.8RT) was applied on the dorsum of the foot, and the withdrawal reflex from the ipsilateral biceps femoris muscle was measured. The subjects scored the pain intensity on a visual analogue scale (0-100 mm) for the beginning, the middle and the end phase of the 5 s series of stimulation, and the respective averaged reflex size was calculated. The reflex size increased at stimulus frequencies 10 Hzx0.8RT and 20 Hzx0.8RT as compared with 5 Hzx0.8RT (SNK, P<0.05), and by an increase in current intensity from 0.6RT to 0.8RT (SNK, P<0.05). Pain intensity increased with the increase in the current intensity from 0.6RT to 0.8RT (SNK, P<0.05). Profound activation of inhibition following electrocutaneous pain stimuli was demonstrated by reduction in pain intensity and reflex size during the last second as compared with the first second at 0.6RT current intensity (SNK, P<0.05). The pain intensity peaked between 5 and 10 Hz (P<0.05) and was reduced at 20 Hz for current intensities at 0.8RT (P<0.05). This study provides evidence for both frequency dependent central integration of the repetitive electrocutaneous stimuli and activation of a pain inhibitory system by psychophysical and electrophysiological means, demonstrating the delicate balance between neuronal facilitation and inhibition in the human pain system.

Adult↗
PubMed1998

Three ulnar nerve conduction studies in patients with ulnar neuropathy at the elbow.

OBJECTIVE: Ulnar neuropathy at the elbow is often difficult to localize by standard electrophysiologic testing. This study compared three ulnar nerve conduction studies to determine which was more sensitive in localizing ulnar neuropathy at the elbow. METHODS: Motor studies to the first dorsal interosseous and the abductor digiti quinti and a mixed ulnar nerve sensory study across the elbow. RESULTS: Motor studies to the first dorsal interosseous and abductor digiti quinti were abnormal in 81% and 71% of patients, respectively. The ulnar mixed sensory study across the elbow was abnormal in 57%. In 38%, all three tests were abnormal. CONCLUSION: Motor studies were more sensitive than the ulnar mixed sensory study across the elbow in localizing ulnar neuropathy of the elbow.

Adult↗
PubMed2000

The anatomical organization of the macaque pregeniculate complex.

Saccade-related activity recorded in the primate pregeniculate nucleus, and its anatomical connections with the pretectal nucleus of the optic tract (NOT) and superior colliculus (SC), suggest that it plays a role in visual-ocular motor integration. To study this role, a clearer understanding of pregeniculate organization is required. Based on its connectivity and neurotransmitter immunocytochemistry, we demonstrate that this nucleus is composed of several subnuclei, suggesting the term, pregeniculate complex (PrGC). The PrGC includes a weakly developed dorsal lamina, rostrally, and a well-developed ventral lamina. The ventral lamina includes the retinorecipient and superior sublayers, rostrally, and the medial division, caudally. A thin lamina of cells lateral to the dorsal lateral geniculate nucleus is contiguous with the PrGC; we term this the lateral division. The PrGC and the lateral division each project to the SC/NOT; the superior sublayer and medial division of the PrGC are connected reciprocally to the SC/NOT. Immunocytochemistry for gamma-aminobutyric acid (GABA) and substance P (SP) further delineate the PrGC subnuclei. The retinorecipient sublayer stains most intensely for GABA and SP. The superior sublayer and medial division also stain strongly for GABA and SP. Essentially all neurons in the lateral division are GABA-positive. The combination of tract tracing and immunocytochemistry demonstrate differences in the connectivity of the PrGC subnuclei and the lateral division with the SC/NOT. This, combined with the differential localization of GABA in the PrGC, provides a basis for further study of its functional role.

Afferent Pathways↗
PubMed2001

Postsynaptic dorsal column and cuneate neurons in raccoon: comparison of response properties and cross-correlation analysis.

The responses of 111 postsynaptic dorsal column (PSDC) neurons in the cervical spinal cord and 51 cuneate neurons with receptive fields on the glabrous skin of the forepaw were studied in anesthetized raccoons using extracellular recording techniques. The PSDC neurons had larger receptive fields than the cuneate neurons, but in both groups the fields never extended onto hairy skin. PSDC and cuneate neurons had approximately the same mean latency to electrical stimulation of the receptive field, but PSDC neurons had significantly lower thresholds. The majority of both PSDC and cuneate neurons also responded to electrical stimulation of an adjacent digit, even though they did not respond to mechanical stimulation of that digit. Cross-correlation analysis of the activity of 51 pairs of PSDC and cuneate neurons recorded simultaneously revealed a significant interaction in 26 pairs during spontaneous activity. In 20 of these neuron pairs, the probability that the cuneate neuron would fire was greater after the PSDC neuron had fired (suggesting a spinocuneate interaction), five pairs showed an interaction in the opposite (cuneospinal) direction, and one pair had a significant inhibitory interaction. These interactions occurred more often when the receptive fields of the two neurons were overlapping than when their fields were on adjacent digits. Frequency response analysis revealed greater coherence for those pairs showing a spinocuneate interaction than for those with a cuneospinal interaction. These results support the hypothesis that the PSDC system exerts a tonic facilitatory effect on cuneate neurons and that there may be some somatotopic organization to the interactions. However, the similar response latencies of the two groups of neurons makes it unlikely that PSDC neurons could contribute to the rapid initial processing of cutaneous information by the cuneate nucleus.

Action Potentials↗
PubMed2004

Key mechanisms for setting the input-output gain across the motoneuron pool.

This chapter summarizes a number of factors that control the "input-output" function across the motoneurons (MNs) comprising a single spinal motor nucleus. The main focus is on intrinsic properties of individual MNs that can be controlled by neuromodulators. These include: (1) amplification of the synaptic input at the cell's dendritic level by voltage-gated, persistent inward currents (plateau potentials); and (2) transduction of the net synaptic excitation into a frequency code (the MN's stimulus current-spike frequency relation) at the cell's soma/initial segment. Two other aspects of the synaptic control of MNs, which may affect their input-output gain, are also discussed. They include the hypotheses that: (1) a non-uniform distribution of synaptic effects to low- and high-threshold motor units causes a change in recruitment gain; and (2) recurrent inhibition, via motor axon collaterals and Renshaw cells, functions as a variable gain regulator of MN discharge.

Action Potentials↗
PubMed1991

Noradrenergic locus coeruleus neurons: their distant connections and their relationship to neighboring (including cholinergic and GABAergic) neurons of the central gray and reticular formation.

Noradrenergic LC neurons appear to be relatively unique in the brain, being unsurpassed in the divergence and ubiquity of their projections through the central nervous system. In this regard, they share certain characteristics with peripheral noradrenaline neurons of the sympathetic nervous system. As such they would be assumed to play a very general role in modulating the activity of large populations of neurons in multiple, functionally diverse systems. Like other periventricular and reticular neurons, they have the potential to receive afferent information from multiple sources via long dendrites, upon which the majority of their inputs from brainstem and forebrain may arrive. They appear closely related to the cholinergic neurons of the laterodorsal tegmental nucleus, their neighbors that are located medial and rostral to them within the periventricular gray and that have similarly oriented and positioned long dendrites that would allow reception of similar afferent input as the LC neurons and also possibly interaction with the LC neurons. As evidenced by input to the noradrenergic cell bodies in the compact portion of the nucleus, a moderate GABAergic innervation, that may derive in part from local neurons, could have a potent influence on the activity of the cells. Periventricular GABAergic cells could also serve as intermediaries to other afferent input, from a distance, terminating in the periventricular region or from local neurons such as the cholinergic cells of the laterodorsal tegmental nucleus.

Acetylcholine↗
PubMed1996

Neurophysiology of micturition and continence.

This article reviews the neuroanatomy, neurophysiology, and neuropharmacology involved in micturition and continence. Knowledge of these topics helps the clinician diagnose and treat voiding disorders that are caused by disease, trauma, drugs, and aging.

Afferent Pathways↗
PubMed1997

Esophageal distension induced gastric relaxation is mediated in part by vagal peripheral reflex mechanism in rats.

The effect of short-term lower esophageal distension on intragastric pressure (IGP) and the related neural pathways involved were investigated in urethane-anesthetized rats in which enteric nervous system connections were interrupted by ligations of the pylorus and the gastroesophageal junction while keeping the gastric vagus nerve trunks intact. Under these conditions, lower esophageal distension with a bolus of 0.2 to 0.5 ml saline in 0.1 ml step increments, raised the inside esophagus balloon pressure from 1.89 +/- 0.17 to 4.21 +/- 0.13 cm H2O and reduced IGP from -0.42 +/- 0.08 to -0.77 +/- 0.12 cm H2O, respectively. Bilateral cervical vagotomy partly blocked the gastric relaxation induced by 0.5 ml esophageal distension from -0.77 +/- 0.12 to -0.34 +/- 0.02 cm H2O; in contrast, a further bilateral splanchnectomy partly rebounded the effect of 0.5 ml esophageal distension from -0.34 +/- 0.02 to -0.46 +/- 0.05 cm H2O. These results suggest that the enteric nervous system may not play a prominent role in acute esophageal distension induced-gastric relaxation. However, more than 50% of this effect is central nervous system mediated (via the long vago-vagal reflex). The other 40% can be maintained without central and enteric nervous systems involvement, probably via a proposed gastric vagal afferent-esophageal collateral reflex.

Afferent Pathways↗