scholarly journals Endogenous Kisspeptin Tone Is a Critical Excitatory Component of Spontaneous GnRH Activity and the GnRH Response to NPY and CART

2014 ◽  
Vol 99 (3-4) ◽  
pp. 190-203 ◽  
Author(s):  
Saurabh Verma ◽  
Melissa A. Kirigiti ◽  
Robert P. Millar ◽  
Kevin L. Grove ◽  
M. Susan Smith
Keyword(s):  
Excitatory Component

Somatosensory cortical efferent neurons of the awake rabbit: latencies to activation via supra--and subthreshold receptive fields

1996 ◽  
Vol 75 (4) ◽  
pp. 1753-1759 ◽  
Author(s):  
H. A. Swadlow ◽  
T. P. Hicks
Keyword(s):  
High Speed ◽  
Receptive Fields ◽  
Cortical Cell ◽  
Sensory Stimulation ◽  
Inhibitory Response ◽  
Postsynaptic Potentials ◽  
Peripheral Stimulation ◽  
Efferent Neurons ◽  
Excitatory Component ◽  
Peripheral Sensory

1. Latencies to peripheral sensory stimulation were examined in four classes of antidromically identified efferent neurons in the primary somatosensory cortex (S1) of awake rabbits. Both suprathreshold responses (action potentials) and subthreshold responses were examined. Subthreshold responses were examined by monitoring the thresholds of efferent neurons to juxtasomal current pulses (JSCPs) delivered through the recording microelectrode (usually 1-3 microA). Through the use of this method, excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) were manifested as decreases and increases in threshold, respectively. Efferent populations examined included callosal (CC) neurons, ipsilateral corticocortical (C-IC) neurons, and descending corticofugal neurons of layer 5 (CF-5) and layer 6 (CF-6). Very brief air puffs (rise and fall times 0.6 ms) were delivered to the receptor periphery via a high-speed solenoid valve. 2. Whereas all CF-5 neurons had demonstrable suprathreshold excitatory and/or inhibitory responses to peripheral stimulation, most CC, C-IC, and CF-6 neurons did not. CC and CF-6 neurons that yielded no suprathreshold response to the stimulus had lower axonal conduction velocities than those that did respond (P < 0.0001 in both cases). However, subthreshold receptive fields could be demonstrated in many of the otherwise unresponsive CC (81%), C-IC (88%), and CF-6 (43%) neurons. The subthreshold responses usually consisted of an initial excitatory component (a decrease in the threshold to the JSCP) and a subsequent long-duration (> 80 ms) inhibitory component. A few neurons (1 CC, 1 C-IC, and 5 CF-6) showed an initial short latency inhibitory response in the absence of any excitatory component. 3. Some CC and C-IC neurons yielded supra- and/or subthreshold responses to peripheral stimulation at latencies of 6.1-7 ms. All such neurons were found at intermediate cortical depths (thought to correspond to deep layer 2-3 through layer 5). It is argued that such latencies are indicative of monosynaptic activation via thalamic afferents. Very superficial CC and C-IC neurons, and all CF-6 neurons responded to latencies of > 7 ms. All CF-5 neurons responded to latencies of > 8 ms, although many were found at the same depth as the deeper CC and C-IC neurons that responded at monosynaptic latencies. These results indicate that cortical cell type as well as laminar position are important factors that determine the sequence of intracortical neuronal activation after peripheral sensory stimulation.

Behavioral Time Course of Microstimulation in Cortical Area MT

2010 ◽  
Vol 103 (1) ◽  
pp. 334-345 ◽  
Author(s):  
Nicolas Y. Masse ◽  
Erik P. Cook
Keyword(s):  
Electrical Stimulation ◽  
Time Course ◽  
Behavioral Effects ◽  
Sensory Stimuli ◽  
Temporal Properties ◽  
Behavioral Studies ◽  
Electrophysiological Studies ◽  
Excitatory Component ◽  
Sensory Neural

Electrical stimulation of the brain is a valuable research tool and has shown therapeutic promise in the development of new sensory neural prosthetics. Despite its widespread use, we still do not fully understand how current passed through a microelectrode interacts with functioning neural circuits. Past behavioral studies have suggested that weak electrical stimulation (referred to as microstimulation) of sensory areas of cortex produces percepts that are similar to those generated by normal sensory stimuli. In contrast, electrophysiological studies using in vitro or anesthetized preparations have shown that neural activity produced by brief microstimulation is radically different and longer lasting than normal responses. To help reconcile these two aspects of microstimulation, we examined the temporal properties that microstimulation has on visual perception. We found that brief application of subthreshold microstimulation in the middle temporal (MT) area of visual cortex produced smaller and longer-lasting effects on motion perception compared with an equivalent visual stimulus. In agreement with past electrophysiological studies, a computer simulation reproduced our behavioral effects when the time course of a single microstimulation pulse was modeled with three components: an immediate fast strong excitatory component, followed by a weaker inhibitory component, and then followed by a long duration weak excitatory component. Overall, these results suggest the behavioral effects of microstimulation in our experiments were caused by the unique and long-lasting temporal effects microstimulation has on functioning cortical circuits.

Responses of ferret lower esophageal sphincter to 5-hydroxytryptamine: pathways and receptor subtypes

1995 ◽  
Vol 268 (6) ◽  
pp. G1004-G1011 ◽  
Author(s):  
L. A. Blackshaw ◽  
V. Nisyrios ◽  
J. Dent
Keyword(s):  
Lower Esophageal Sphincter ◽  
Splanchnic Nerve ◽  
Lower Esophageal Sphincter Pressure ◽  
Receptor Subtypes ◽  
Sphincter Pressure ◽  
In Series ◽  
Bilateral Vagotomy ◽  
Excitatory Component ◽  
Esophageal Sphincter ◽  
Greater Splanchnic Nerve

In urethananesthetized ferrets, basal lower esophageal sphincter pressure (LESP) was unaffected by the 5-hydroxytryptamine3 (5-HT3) receptor antagonist granisetron (0.5 mg/kg) or by greater splanchnic nerve section (GSX), but increased after bilateral vagotomy. Peripheral vagal nerve stimulation caused LES relaxation, often followed by a brief contraction and a prolonged inhibition of LESP. Close intra-arterial injection of 5-HT (5-100 micrograms) had a biphasic effect on LESP, with a brief drop followed by a prolonged increase. Granisetron (0.5 mg/kg i.v.) abolished the initial relaxation and revealed an earlier peak of excitation. This was not influenced by subsequent vagotomy and GSX. In a series of eight additional experiments (series 2), granisetron was given after vagotomy and GSX. In series 2, 5-HT-induced relaxation was unaffected by vagotomy but was significantly reduced after GSX and was further reduced after granisetron, indicating that 5-HT3 receptor mechanisms may lie on a sympathetic neural pathway. Vagotomy had no effect on the excitatory component. GSX had no effect on the amplitude of excitation, but reduced its latency. Granisetron had no further effect on excitation in series 2. In a separate series of 13 experiments (series 3), the excitatory component of the LES response to 5-HT was abolished by ketanserin (2.5 mg/kg i.v.) , after which only relaxation occurred. Both 5-HT2 and 5-HT3 antagonists in combination abolished all effects of 5-HT on LESP. Atropine (400 micrograms/kg i.v., n = 7) had no effect on 5-HT-induced LES responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of synaptic facilitation during the progression of kindling epilepsy by amygdala stimulations

1993 ◽  
Vol 70 (2) ◽  
pp. 602-609 ◽  
Author(s):  
S. Matsuura ◽  
K. Hirayama ◽  
R. Murata
Keyword(s):  
Quantitative Analysis ◽  
Long Term Potentiation ◽  
Progressive Increase ◽  
Friedman Test ◽  
Single Test ◽  
Term Potentiation ◽  
Excitatory Component ◽  
Activity Dependent ◽  
Excitatory Potential

1. A quantitative analysis of facilitation during the kindling stimulation to the amygdala was conducted by measuring the area between the excitatory potential and the baseline in the averaged tetanic response recorded at the entorhinal cortex. The changes in facilitation were then compared with the development of electrographic afterdischarges (AD) and behavioral seizures in response to successive kindling stimulations. 2. Kindling train pulses (n = 99 or 100; duration: 0.5 ms; frequency: 10 Hz; intensity: AD threshold) were applied to conscious rats until at least one generalized seizure occurred or until 13 stimuli were delivered. 3. Facilitation of the entorhinal responses by kindling stimulation first occurred in the monosynaptic excitatory component and was then followed by a progressive increase in the polysynaptic component that was manifested as the later negative peaks. A clear progressive enhancement was observed in the facilitation by successive kindling stimulations, which also induced prolongation of the AD duration and progression of the seizure stages, indicating that activity-dependent enhancement of facilitation (EF) occurred during the progression of kindling epilepsy. 4. Quantitative analysis revealed that the EF that occurred with the progression of seizure stages was statistically significant (P < 0.001, Friedman test). The AD duration (r = 0.89) and the long-term potentiation (r = 0.85) of the entorhinal responses by single test amygdala stimuli showed a very good linear relation to the EF.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Activation and Reconfiguration of Fictive Feeding by the OctopamineContaining Modulatory OC Interneurons in the SnailLymnaea

2001 ◽  
Vol 86 (2) ◽  
pp. 792-808 ◽  
Author(s):  
Ágnes Vehovszky ◽  
Christopher J. H. Elliott
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Feeding Rate ◽  
Lymnaea Stagnalis ◽  
Repetitive Stimulation ◽  
Excitatory Effect ◽  
Excitatory Component ◽  
Inhibitory Components ◽  
Stimulation Of

We describe the role of the octopamine-containing OC interneurons in the buccal feeding system of Lymnaea stagnalis. OC neurons are swallowing phase interneurons receiving inhibitory inputs in the N1 and N2 phases, and excitatory inputs in the N3 phase of fictive feeding. Although the OC neurons do not always fire during feeding, the feeding rate is significantly ( P < 0.001) higher when both SO and OC fire in each cycle than when only the SO fires. In 28% of silent preparations, a single stimulation of an OC interneuron evokes the feeding pattern. Repetitive stimulation of the OC interneuron increases the proportion of responsive preparations to 41%. The OC interneuron not only changes both the feeding rate and reconfigures the pattern. Depolarization of the OC interneurons increases the feeding rate and removes the B3 motor neuron from the firing sequence. Hyperpolarization slows it down (increasing the duration of N1 and N3 phases) and recruits the B3 motor neuron. OC interneurons form synaptic connections onto buccal motor neurons and interneurons but not onto the cerebral (cerebral giant cell) modulatory neurons. OC interneurons are electrically coupled to all N3 phase (B4, B4Cl, B8) feeding motor neurons. They form symmetrical connections with the N3p interneurons having dual electrical (excitatory) and chemical (inhibitory) components. OC interneurons evoke biphasic synaptic inputs on the protraction phase interneurons (SO, N1L, N1M), with a short inhibition followed by a longer lasting depolarization. N2d interneurons are hyperpolarized, while N2v interneurons are slowly depolarized and often fire a burst after OC stimulation. Most motor neurons also receive synaptic responses from the OC interneurons. Although OC and N3p interneurons are both swallowing phase interneurons, their synaptic contacts onto follower neurons are usually different (e.g., the B3 motor neurons are inhibited by OC, but excited by N3p interneurons). Repetitive stimulation of OC interneuron facilitates the excitatory component of the biphasic responses evoked on the SO, N1L, and N1M interneurons, but neither the N2 nor the N3 phase interneurons display a similar longer-lasting excitatory effect. OC interneurons are inhibited by all the buccal feeding interneurons, but excited by the serotonergic modulatory CGC neurons. We conclude that OC interneurons are a new kind of swallowing phase interneurons. Their connections with the buccal feeding interneurons can account for their modulatory effects on the feeding rhythm. As they contain octopamine, this is the first example in Lymnaea that monoaminergic modulation and reconfiguration are provided by an intrinsic member of the buccal feeding network.

Frequency dependence of synaptic transmission in nucleus of the solitary tract in vitro

1986 ◽  
Vol 55 (5) ◽  
pp. 1076-1090 ◽  
Author(s):  
R. Miles
Keyword(s):  
Frequency Dependence ◽  
Stimulus Frequency ◽  
Cardiovascular Reflexes ◽  
Solitary Tract ◽  
Postsynaptic Inhibition ◽  
Similar Frequency ◽  
Synaptic Circuits ◽  
Long Latency ◽  
Excitatory Component

Afferent fibers from visceral sensory receptors enter the medulla oblongata, form the solitary tract, and synapse with neurons in the nucleus of the solitary tract. In the present study longitudinal slices were prepared from guinea pig medulla in order to examine the properties of transmission at these synapses in vitro. Synaptic responses to selective stimulation of solitary tract fibers were recorded intracellularly from neurons in an area, close to the obex and immediately medial and lateral to the tract, where arterial baroreceptor fibers are known to terminate. The amplitude of maximally evoked postsynaptic potentials (PSPs) in solitary tract neurons was strongly dependent on stimulus frequency. On increasing frequency from 0.5 to 20 Hz, a PSP depression of 80% was reached in 4-8 s. The mean depression was 35% at 5 Hz and 60% at 10 Hz. Sufficient local connections were retained in vitro that solitary tract stimulation evoked disynaptic inhibitory potentials and long latency, possibly polysynaptic, excitatory potentials in some neurons. The possibility that frequency-dependent changes in the efficacy of these local synaptic circuits contributed to PSP depression was examined. The role of postsynaptic inhibition in synaptic depression was tested by examining the frequency dependence of PSPs at membrane potentials close to the reversal of their excitatory component. The resulting hyperpolarizing PSPs were also depressed suggesting that a facilitation of postsynaptic inhibition at high frequency does not underlie the depression. The contribution of depression in multisynaptic excitatory pathways to PSP depression was assessed by exclusion. At low stimulus intensities, excitatory synaptic events with no long latency components were evoked. These events exhibited a similar frequency dependence to that of maximal PSPs. These results suggest that mechanisms operating at synapses made by solitary tract fibers are responsible for the frequency dependence of PSPs recorded in solitary tract neurons. Such mechanisms might contribute to the adaptation of some cardiovascular reflexes initiated by baroreceptors.

Medullary pathway of the Bezold-Jarisch reflex in the rat

1992 ◽  
Vol 263 (6) ◽  
pp. R1195-R1202 ◽  
Author(s):  
A. J. Verberne ◽  
P. G. Guyenet
Keyword(s):  
Kynurenic Acid ◽  
Jugular Vein ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Solitary Tract Nucleus ◽  
Solitary Tract ◽  
Arterial Baroreflex ◽  
Glutamate Antagonist ◽  
Excitatory Component ◽  
Sympathetic Discharge

The central pathway mediating the Bezold-Jarisch reflex elicited by jugular vein injection of serotonin (5-HT) and phenyl biguanide (PBG) was studied in halothane-anesthetized, paralyzed rats. 5-HT and PBG produced hypotension and inhibition of lumbar sympathetic discharge often preceded by sympathoexcitation. The Bezold-Jarish reflex was blocked by bilateral kynurenic acid (KYN; glutamate antagonist, 1.25 nmol/side) microinjection into the solitary tract nucleus. Bilateral KYN injection into the caudal ventrolateral medulla (5 nmol/side) also blocked the reflex. Bilateral injection of bicuculline methiodide (BIC; 100 pmol/side) into the rostral ventrolateral medulla (RVL) reduced the depressor and sympathoinhibitory components of the reflex and enhanced an excitatory component. Blockade or attenuation of the Bezold-Jarisch reflex was always associated with a concomitant blockade or attenuation of the arterial baroreflex. RVL barosensitive neurons (n = 61) were inhibited (> 60% reduction in firing) by PBG and 5-HT. Iontophoretic application of BIC (n = 11 cells), but not strychnine (glycine antagonist), blocked inhibition of RVL neurons by 5-HT and PBG. The sympathoinhibitory component of the Bezold-Jarisch reflex may use a central pathway similar to that of the arterial baroreflex.

Reticulospinal vasomotor neurons in the RVL mediate the somatosympathetic reflex

1989 ◽  
Vol 256 (5) ◽  
pp. R1084-R1097 ◽  
Author(s):  
S. F. Morrison ◽  
D. J. Reis
Keyword(s):  
Splanchnic Nerve ◽  
Ventrolateral Medulla ◽  
Conduction Time ◽  
Sympathetic Response ◽  
Early Activation ◽  
Afferent Activation ◽  
Somatosympathetic Reflex ◽  
Excitatory Component ◽  
Root Response ◽  
External Stimuli

Sympathoexcitatory neurons in the C1 area of the rostral ventrolateral medulla (RVL) that project to the spinal intermediolateral nucleus play an important role in the maintenance of basal sympathetic tone and in the reflex adjustments of sympathetic activity to internal and external stimuli. We sought to determine whether the sympathetic response to somatic afferent activation, the somatosympathetic reflex, also arises from the excitation of reticulospinal vasomotor neurons in the RVL. In urethan-anesthetized, paralyzed, ventilated rats, single sciatic nerve stimuli evoked an early (latency: 26 ms) and a late (latency: 117 ms) excitation of antidromically identified, RVL-spinal, sympathoexcitatory neurons that paralleled and preceded the biphasic increases in splanchnic nerve activity (peak latencies: 87 and 176 ms). The differences between the respective latencies of the RVL unit responses and those recorded in the splanchnic nerve were comparable to the conduction time in the sympathoexcitatory pathway from the RVL to the splanchnic nerve. Both the threshold intensity and the response amplitude vs. stimulus intensity relationship for the sympathetic response were comparable to those for the A-delta-fiber component of the dorsal root response to sciatic stimulation. We conclude that the rat somatosympathetic reflex consists of an early excitatory component due to the early activation of RVL-spinal sympathoexcitatory neurons with rapidly conducting axons and a later peak that may arise from the late activation of these same neurons as well as the early activation of RVL vasomotor neurons with more slowly conducting spinal axons.

scholarly journals Circadian variability of body temperature responses to methamphetamine

2018 ◽  
Vol 314 (1) ◽  
pp. R43-R48 ◽  
Author(s):  
Abolhassan Behrouzvaziri ◽  
Maria V. Zaretskaia ◽  
Daniel E. Rusyniak ◽  
Dmitry V. Zaretsky ◽  
Yaroslav I. Molkov
Keyword(s):  
Body Temperature ◽  
Dose Dependence ◽  
The Body ◽  
Sprague Dawley ◽  
Baseline Activity ◽  
Sprague Dawley Rats ◽  
Excitatory Component ◽  
Hyperthermic Response ◽  
Living Organisms ◽  
Temperature Responses

Vital parameters of living organisms exhibit circadian rhythmicity. Although rats are nocturnal animals, most of the studies involving rats are performed during the day. The objective of this study was to examine the circadian variability of the body temperature responses to methamphetamine. Body temperature was recorded in male Sprague-Dawley rats that received intraperitoneal injections of methamphetamine (Meth, 1 or 5 mg/kg) or saline at 10 AM or at 10 PM. The baseline body temperature at night was 0.8°C higher than during the day. Both during the day and at night, 1 mg/kg of Meth induced monophasic hyperthermia. However, the maximal temperature increase at night was 50% smaller than during the daytime. Injection of 5 mg/kg of Meth during the daytime caused a delayed hyperthermic response. In contrast, the same dose at night produced responses with a tendency toward a decrease of body temperature. Using mathematical modeling, we previously showed that the complex dose dependence of the daytime temperature responses to Meth results from an interplay between inhibitory and excitatory drives. In this study, using our model, we explain the suppression of the hyperthermia in response to Meth at night. First, we found that the baseline activity of the excitatory drive is greater at night. It appears partially saturated and thus is additionally activated by Meth to a lesser extent. Therefore, the excitatory component causes less hyperthermia or becomes overpowered by the inhibitory drive in response to the higher dose. Second, at night the injection of Meth results in reduction of the equilibrium body temperature, leading to gradual cooling counteracting hyperthermia.

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