In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. I. Membrane and synaptic response properties

1995 ◽  
Vol 73 (2) ◽  
pp. 780-793 ◽  
Author(s):  
S. H. Wu ◽  
J. B. Kelly

1. We examined the physiological properties of neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the rat in a 400-microns tissue slice taken in the frontal plane through the auditory midbrain. The brain slice was placed in a small chamber and was perfused fully submerged in a warm, continuously circulating oxygenated saline solution. We made intracellular recordings with glass pipettes filled with 4 M potassium acetate. Synaptic potentials were evoked by electrical stimulation of either the lateral lemniscus or the commissure of Probst. 2. We tested the membrane characteristics of DNLL neurons by recording the electrical potentials produced by intracellular injection of positive or negative current. Typically, DNLL neurons had nearly linear current-voltage curves and responded to depolarizing currents with a sustained train of action potentials. Injection of intense or prolonged depolarizing currents frequently resulted in a pronounced afterhyperpolarization of the cell membrane. Intense hyperpolarizing currents were often followed by a large rebound depolarization. 3. The action potentials of most DNLL neurons were characterized by a double undershoot, i.e., the initial hyperpolarization after a spike was followed by a second, longer-latency hyperpolarization. Seventy-nine percent of the cells recorded had this type of double undershoot. The remaining cells had a single undershoot in which the postspike hyperpolarization was followed by a steady return to resting potential without any indication of a second phase of hyperpolarization. 4. Electrical stimulation of the lateral lemniscus evoked both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in DNLL. The EPSPs were evoked alone without any evidence of an IPSP in 67% of neurons and IPSPs were evoked alone in 6% of the neurons from which recordings were made. In 27% of the recordings both EPSPs and IPSPs were elicited in the same neuron by stimulation of a single location on the lateral lemniscus. 5. The combined EPSPs and IPSPs produced by lemniscal stimulation could often be dissociated by their different thresholds and/or different response latencies. For 35% of the neurons in which both an EPSP and IPSP were present, the IPSP had a lower threshold; for 23% of the cells, the EPSP had a lower threshold. For the remaining cells the thresholds for producing an EPSP and IPSP were the same. 6. DNLL neurons were capable of responding with great fidelity to a single pulse of stimulation delivered to the lateral lemniscus, i.e., an action potential was evoked after every stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

1996 ◽  
Vol 75 (3) ◽  
pp. 1271-1282 ◽  
Author(s):  
S. H. Wu ◽  
J. B. Kelly

1. The synaptic pharmacology of the dorsal nucleus of the lateral lemniscus (DNLL) of the rat was investigated in a brain slice preparation of the auditory midbrain. The brain slice was cut in the coronal plane and placed in a small recording chamber where warm, oxygenated saline was continuously perfused over and underneath the tissue. Intracellular recordings were made with glass microelectrodes filled with 4 M potassium acetate. Synaptic potentials were elicited by electrical stimulation of the lateral lemniscus or commissure of Probst and pharmacological effects were tested by bath application of amino acid agonists and antagonists. 2. The cells in DNLL were challenged with the excitatory amino acid (EAA) agonists, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), N-methyl-D-aspartic acid (NMDA) in 0 Mg2+, and L-glutamate. Each of these caused a depolarization of the cell membrane, a reduction in cell membrane resistance, and the onset of spontaneous firing. 3. Short-latency excitatory postsynaptic potentials (EPSPs) were evoked by stimulation of the lateral lemniscus in 77% of the neurons tested. The mean latency to initial depolarization was 0.9 ms. A single spike with relatively constant latency (mean 1.5 ms) was typically elicited when the strength of lemniscal stimulation was increased. A longer-latency EPSP (mean 2.9 ms) was seen in 34% of the neurons tested either with the slice in normal saline or after pharmacological block of the earlier, short-latency EPSP. The long-latency EPSP was followed by a single spike of multiple spikes with highly variable latencies (range 3.2-24 ms). In 28% of the neurons tested, both early and late EPSPs were observed in response to stimulation of a single location on the lateral lemniscus. 4. Stimulation of the commissure of Probst elicited short-latency EPSPs (mean 0.9 ms) in 37% of the neurons tested. Longer-latency EPSPs (mean 3.0 ms) were found in only 3% of the neurons in response to commissural stimulation. 5. The nonspecific EAA antagonist kynurenic acid blocked both short-and long-latency EPSPs evoked by either lemniscal or commissural stimulation. The non-NMDA antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), at very low concentrations, blocked the short-latency EPSPs but had no effect on the longer-latency EPSPs. The short-latency EPSPs were unaffected by the NMDA antagonist D,L-2-amino-5-phosphonovaleric acid (APV). In contrast, the longer-latency EPSPs were blocked by APV, but never by CNQX. 6. DNLL neurons were affected by the inhibitory amino acid agonists gamma-aminobutyric acid (GABA) and glycine. The membrane resistance of the neurons was decreased by GABA and glycine in a solution of either normal or calcium-free saline in a concentration-dependent manner. 7. Inhibitory postsynaptic potentials (IPSPs) were elicited by stimulation of the lateral lemniscus in 53% of the neurons and the commissure of the Probst in 18% of the neurons tested. The mean latencies were 1.0 and 0.9 ms, respectively. The reversal potentials of the IPSPs were around -70 mV. 8. The IPSPs evoked by stimulation of the lateral lemniscus were blocked by the glycine receptor antagonist strychnine, but not by the GABA receptor antagonist bicuculline, whereas the IPSPs elicited by stimulation of the commissure of Probst were blocked by bicuculline but not strychnine.


1988 ◽  
Vol 118 (3) ◽  
pp. 471-483 ◽  
Author(s):  
L. M. Voloschin ◽  
E. Décima ◽  
J. H. Tramezzani

ABSTRACT Electrical stimulation of the XIII thoracic nerve (the 'mammary nerve') causes milk ejection and the release of prolactin and other hormones. We have analysed the route of the suckling stimulus at the level of different subgroups of fibres of the teat branch of the XIII thoracic nerve (TBTN), which innervates the nipple and surrounding skin, and assessed the micromorphology of the TBTN in relation to lactation. There were 844 ± 63 and 868 ± 141 (s.e.m.) nerve fibres in the TBTN (85% non-myelinated) in virgin and lactating rats respectively. Non-myelinated fibres were enlarged in lactating rats; the modal value being 0·3–0·4 μm2 for virgin and 0·4–0·5 μm2 for lactating rats (P > 0·001; Kolmogorov–Smirnov test). The modal value for myelinated fibres was 3–6 μm2 in both groups. The compound action potential of the TBTN in response to electrical stimulation showed two early volleys produced by the Aα- and Aδ-subgroups of myelinated fibres (conduction velocity rate of 60 and 14 m/s respectively), and a late third volley originated in non-myelinated fibres ('C') group; conduction velocity rate 1·4 m/s). Before milk ejection the suckling pups caused 'double bursts' of fibre activity in the Aδ fibres of the TBTN. Each 'double burst' consisted of low amplitude action potentials and comprised two multiple discharges (33–37 ms each) separated by a silent period of around 35 ms. The 'double bursts' occurred at a frequency of 3–4/s, were triggered by the stimulation of the nipple and were related to fast cheek movements visible only by watching the pups closely. In contrast, the Aα fibres of the TBTN showed brief bursts of high amplitude potentials before milk ejection. These were triggered by the stimulation of cutaneous receptors during gross slow sucking motions of the pup (jaw movements). Immediately before the triggering of milk ejection the mother was always asleep and a low nerve activity was recorded in the TBTN at this time. When reflex milk ejection occurred, the mother woke and a brisk increase in nerve activity was detected; this decreased when milk ejection was accomplished. In conscious rats the double-burst type of discharges in Aδ fibres was not observed, possibly because this activity cannot be detected by the recording methods currently employed in conscious animals. During milk ejection, action potentials of high amplitude were conveyed in the Aα fibres of the TBTN. During the treading time of the stretch reaction (SR), a brisk increase in activity occurred in larger fibres; during the stretching periods of the SR a burst-type discharge was again observed in slow-conducting afferents; when the pups changed nipple an abrupt increase in activity occurred in larger fibres. In summary, the non-myelinated fibres of the TBTN are increased in diameter during lactation, and the pattern of suckling-evoked nerve activity in myelinated fibres showed that (a) the double burst of Aδ fibres, produced by individual sucks before milk ejection, could be one of the conditions required for the triggering of the reflex, and (b) the nerve activity displayed during milk-ejection action may result, at least in part, from 'non-specific' stimulation of cutaneous receptors. J. Endocr. (1988) 118, 471–483


2000 ◽  
Vol 203 (3) ◽  
pp. 435-445
Author(s):  
M. Wildman

The position of the coxal segment of the locust hind leg relative to the thorax is monitored by a variety of proprioceptors, including three chordotonal organs and a myochordotonal organ. The sensory neurons of two of these proprioceptors, the posterior joint chordotonal organ (pjCO) and the myochordotonal organ (MCO), have axons in the purely sensory metathoracic nerve 2C (N2C). The connections made by these afferents with metathoracic motor neurons innervating thoraco-coxal and wing muscles were investigated by electrical stimulation of N2C and by matching postsynaptic potentials in motor neurons with afferent spikes in N2C. Stretch applied to the anterior rotator muscle of the coxa (M121), with which the MCO is associated, evoked sensory spikes in N2C. Some of the MCO afferent neurons make direct excitatory chemical synaptic connections with motor neurons innervating the thoraco-coxal muscles M121, M126 and M125. Parallel polysynaptic pathways via unidentified interneurons also exist between MCO afferents and these motor neurons. Connections with the common inhibitor 1 neuron and motor neurons innervating the thoraco-coxal muscles M123/4 and wing muscles M113 and M127 are polysynaptic. Afferents of the pjCO also make polysynaptic connections with motor neurons innervating thoraco-coxal and wing muscles, but no evidence for monosynaptic pathways was found.


1997 ◽  
Vol 78 (5) ◽  
pp. 2235-2245 ◽  
Author(s):  
Xiao Wen Fu ◽  
Borys L. Brezden ◽  
Shu Hui Wu

Fu, Xiao Wen, Borys L. Brezden, and Shu Hui Wu. Hyperpolarization-activated inward current in neurons of the rat's dorsal nucleus of the lateral lemniscus in vitro. J. Neurophysiol. 78: 2235–2245, 1997. The hyperpolarization-activated current ( I h) underlying inward rectification in neurons of the rat's dorsal nucleus of the lateral lemniscus (DNLL) was investigated using whole cell patch-clamp techniques. Patch recordings were made from DNLL neurons of young rats (21–30 days old) in 400 μm tissue slices. Under current clamp, injection of negative current produced a graded hyperpolarization of the cell membrane, often with a gradual sag in the membrane potential toward the resting value. The rate and magnitude of the sag depended on the amount of hyperpolarizing current. Larger current resulted in a larger and faster decay of the voltage. Under voltage clamp, hyperpolarizing voltage steps elicited a slowly activating inward current that was presumably responsible for the sag observed in the voltage response to a steady hyperpolarizing current recorded under current clamp. Activation of the inward current ( I h) was voltage and time dependent. The current just was seen at a membrane potential of −70 mV and was activated fully at −140 mV. The voltage value of half-maximal activation of I h was −78.0 ± 6.0 (SE) mV. The rate of I h activation was best approximated by a single exponential function with a time constant that was voltage dependent, ranging from 276 ± 27 ms at −100 mV to 186 ± 11 ms at −140 mV. Reversal potential ( E h) of I h current was more positive than the resting potential. Raising the extracellular potassium concentration shifted E h to a more depolarized value, whereas lowering the extracellular sodium concentration shifted E h in a more negative direction. I h was sensitive to extracellular cesium but relatively insensitive to extracellular barium. The current amplitude near maximal-activation (about −140 mV) was reduced to 40% of control by 1 mM cesium but was reduced to only 71% of control by 2 mM barium. When the membrane potential was near the resting potential (about −60 mV), cesium had no effect on the membrane potential, current-evoked firing rate and input resistance but reduced the spontaneous firing. When the membrane potential was more negative than −70 mV, cesium hyperpolarized the cell, decreased current-evoked firing and increased the input resistance. I h in DNLL neurons does not contribute to the normal resting potential but may enhance the extent of excitation, thereby making the DNLL a consistently powerful inhibitory source to upper levels of the auditory system.


2001 ◽  
Vol 86 (5) ◽  
pp. 2583-2596 ◽  
Author(s):  
M.-J. Bourque ◽  
A. Kolta

Numerous evidence suggests that interneurons located in the lateral tegmentum at the level of the trigeminal motor nucleus contribute importantly to the circuitry involved in mastication. However, the question of whether these neurons participate actively to genesis of the rhythmic motor pattern or simply relay it to trigeminal motoneurons remains open. To answer this question, intracellular recordings were performed in an in vitro slice preparation comprising interneurons of the peritrigeminal area (PeriV) surrounding the trigeminal motor nucleus (NVmt) and the parvocellular reticular formation ventral and caudal to it (PCRt). Intracellular and extracellular injections of anterograde tracers were also used to examine the local connections established by these neurons. In 97% of recordings, electrical stimulation of adjacent areas evoked a postsynaptic potential (PSP). These PSPs were primarily excitatory, but inhibitory and biphasic responses were also induced. Most occurred at latencies longer than those required for monosynaptic transmission and were considered to involve oligosynaptic pathways. Both the anatomical and physiological findings show that all divisions of PeriV and PCRt are extensively interconnected. Most responses followed high-frequency stimulation (50 Hz) and showed little variability in latency indicating that the network reliably distributes inputs across all areas. In all neurons but one, excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs) were also elicited by stimulation of NVmt, suggesting the existence of excitatory and inhibitory interneurons within the motor nucleus. In a number of cases, these PSPs were reproduced by local injection of glutamate in lieu of the electrical stimulation. All EPSPs induced by stimulation of PeriV, PCRt, or NVmt were sensitive to ionotropic glutamate receptor antagonists 6-cyano-7-dinitroquinoxaline and d,l-2-amino-5-phosphonovaleric acid, while IPSPs were blocked by bicuculline and strychnine, antagonists of GABAA and glycine receptors. Examination of PeriV and PCRt intrinsic properties indicate that they form a fairly uniform network. Three types of neurons were identified on the basis of their firing adaptation properties. These types were not associated with particular regions. Only 5% of all neurons showed bursting behavior. Our results do not support the hypothesis that neurons of PeriV and PCRt participate actively to rhythm generation, but suggest instead that they are driven by rhythmical synaptic inputs. The organization of the network allows for rapid distribution of this rhythmic input across premotoneuron groups.


1994 ◽  
Vol 71 (6) ◽  
pp. 1999-2013 ◽  
Author(s):  
L. Yang ◽  
G. D. Pollak

1. We studied the monaural and binaural response properties of 99 neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the mustache bat before and during the iontophoretic application of antagonists that blocked gamma-aminobutyric acid-A (GABAA) receptors (bicuculline) or glycine receptors (strychnine). All cells were driven by monaural stimulation of the contralateral ear, whereas monaural stimulation of the ipsilateral ear never evoked discharges. The binaural properties of 81 neurons were determined by holding the intensity constant at the contralateral ear and presenting a variety of intensities to the ipsilateral ear. This procedure generated interaural intensity disparity (IID) functions and allowed us to determine the effect of ipsilaterally evoked inhibition on a constant excitatory drive evoked by the contralateral ear. 2. One of the main findings is that the IID functions in the majority of DNLL neurons were not affected by application of either strychnine or bicuculline. Blocking glycinergic inhibition with strychnine had no effect on the IID functions in 75% of the cells studied. However, strychnine did change the IID functions in approximately 25% of the DNLL population. In those cells glycinergic inhibition appeared to be partially, or, in a few cases, entirely responsible for the ipsilaterally evoked spike suppression. In contrast, blocking GABAergic inhibition with bicuculline had no discernible effect on the ipsilaterally evoked spike suppression in any of the excitatory/inhibitory cells that we recorded. GABAergic inhibition, therefore, plays no role in the formation of IID functions of neurons in the DNLL. Furthermore, the results suggest that glycinergic inhibition also does not contribute to the suppression of spikes evoked by stimulation of the contralateral ear in the vast majority of DNLL neurons. 3. Although the majority of IID functions were not influenced when either GABAergic or glycinergic innervation was blocked, ipsilateral stimulation alone evoked both a glycinergic and GABAergic inhibition in most DNLL cells. These inhibitory events were demonstrated in 18 other cells by evoking discharges with the iontophoretic application of glutamate. Stimulating the ipsilateral ear alone under these conditions caused a suppression of the glutamate-evoked discharges. Furthermore, the spike suppression persisted for a period of time that was longer than the duration of the tone burst at the ipsilateral ear. 4. The application of bicuculline or strychnine had different effects on the glutamate-elicited spikes. Bicuculline reduced the duration of the inhibition, and it was always the latter portion of the inhibition that was abolished by bicuculline. In more than half of the cells studied strychnine also reduced the duration of the inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)


2000 ◽  
Vol 83 (6) ◽  
pp. 3209-3216 ◽  
Author(s):  
Jean-François Perrier ◽  
Boris Lamotte D'Incamps ◽  
Nezha Kouchtir-Devanne ◽  
Léna Jami ◽  
Daniel Zytnicki

The postsynaptic potentials elicited in peroneal motoneurons by either mechanical stimulation of cutaneous areas innervated by the superficial peroneal nerve (SP) or repetitive electrical stimulation of SP were compared in anesthetized cats. After denervation of the foot sparing only the territory of SP terminal branches, reproducible mechanical stimulations were applied by pressure on the plantar surface of the toes via a plastic disk attached to a servo-length device, causing a mild compression of toes. This stimulus evoked small but consistent postsynaptic potentials in every peroneal motoneuron. Weak stimuli elicited only excitatory postsynaptic potentials (EPSPs), whereas increase in stimulation strength allowed distinction of three patterns of response. In about one half of the sample, mechanical stimulation or trains of 20/s electric pulses at strengths up to six times the threshold of the most excitable fibers in the nerve evoked only EPSPs. Responses to electrical stimulation appeared with 3–7 ms central latencies, suggesting oligosynaptic pathways. In another, smaller fraction of the sample, inhibitory postsynaptic potentials (IPSPs) appeared with an increase of stimulation strength, and the last fraction showed a mixed pattern of excitation and inhibition. In 24 of 32 motoneurons where electrical and mechanical effects could be compared, the responses were similar, and in 6 others, they changed from pure excitation on mechanical stimulation to mixed on electrical stimulation. With both kinds of stimulation, stronger stimulations were required to evoke inhibitory postsynaptic potentials (IPSPs), which appeared at longer central latencies than EPSPs, indicating longer interneuronal pathways. The similarity of responses to mechanical and electrical stimulation in a majority of peroneal motoneurons suggests that the effects of commonly used electrical stimulation are good predictors of the responses of peroneal motoneurons to natural skin stimulation. The different types of responses to cutaneous afferents from SP territory reflect a complex connectivity allowing modulations of cutaneous reflex responses in various postures and gaits.


2005 ◽  
Vol 22 (2) ◽  
pp. 227-243 ◽  
Author(s):  
Tatiana Y. Kostrominova ◽  
Douglas E. Dow ◽  
Robert G. Dennis ◽  
Richard A. Miller ◽  
John A. Faulkner

Loss of innervation in skeletal muscles leads to degeneration, atrophy, and loss of force. These dramatic changes are reflected in modifications of the mRNA expression of a large number of genes. Our goal was to clarify the broad spectrum of molecular events associated with long-term denervation of skeletal muscles. A microarray study compared gene expression profiles of 2-mo denervated and control extensor digitorum longus (EDL) muscles from 6-mo-old rats. The study identified 121 genes with increased and 7 genes with decreased mRNA expression. The expression of 107 of these genes had not been identified previously as changed after denervation. Many of the genes identified were genes that are highly expressed in skeletal muscles during embryonic development, downregulated in adults, and upregulated after denervation of muscle fibers. Electrical stimulation of denervated muscles preserved muscle mass and maximal force at levels similar to those in the control muscles. To understand the processes underlying the effect of electrical stimulation on denervated skeletal muscles, mRNA and protein expression of a number of genes, identified by the microarray study, was compared. The hypothesis was that loss of nerve action potentials and muscle contractions after denervation play the major roles in upregulation of gene expression in skeletal muscles. With electrical stimulation of denervated muscles, the expression levels for these genes were significantly downregulated, consistent with the hypothesis that loss of action potentials and/or contractions contribute to the alterations in gene expression in denervated skeletal muscles.


Spine ◽  
2000 ◽  
Vol 25 (4) ◽  
pp. 411-417 ◽  
Author(s):  
Yuzuru Takahashi ◽  
Jiro Hirayama ◽  
Yoshio Nakajima ◽  
Seiji Ohtori ◽  
Kazuhisa Takahashi

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