scholarly journals Firing characteristics of deep dorsal horn neurons after acute spinal transection during administration of agonists for 5-HT1B/1D and NMDA receptors

2016 ◽  
Vol 116 (4) ◽  
pp. 1644-1653 ◽  
Author(s):  
Theeradej Thaweerattanasinp ◽  
Charles J. Heckman ◽  
Vicki M. Tysseling
Keyword(s):  
Spinal Cord ◽  
Firing Rate ◽  
Dorsal Horn ◽  
Muscle Spasm ◽  
Spontaneous Firing ◽  
Burst Neurons ◽  
Muscle Spasms ◽  
Firing Characteristics ◽  
Spontaneous Firing Rate ◽  
Excitatory Drive

Spinal cord injury (SCI) results in a loss of serotonin (5-HT) to the spinal cord and a loss of inhibition to deep dorsal horn (DDH) neurons, which produces an exaggerated excitatory drive to motoneurons. The mechanism of this excitatory drive could involve the DDH neurons triggering long excitatory postsynaptic potentials in motoneurons, which may ultimately drive muscle spasms. Modifying the activity of DDH neurons with drugs such as NMDA or the 5-HT1B/1D receptor agonist zolmitriptan could have a large effect on motoneuron activity and, therefore, on muscle spasms. In this study, we characterize the firing properties of DDH neurons after acute spinal transection in adult mice during administration of zolmitriptan and NMDA, using the in vitro sacral cord preparation and extracellular electrophysiology. DDH neurons can be categorized into three major types with distinct evoked and spontaneous firing characteristics: burst (bursting), simple (single spiking), and tonic (spontaneously tonic firing) neurons. The burst neurons likely contribute to muscle spasm mechanisms because of their bursting behavior. Only the burst neurons show significant changes in their firing characteristics during zolmitriptan and NMDA administration. Zolmitriptan suppresses the burst neurons by reducing their evoked spikes, burst duration, and spontaneous firing rate. Conversely, NMDA facilitates them by enhancing their burst duration and spontaneous firing rate. These results suggest that zolmitriptan may exert its antispastic effect on the burst neurons via activation of 5-HT1B/1D receptors, whereas activation of NMDA receptors may facilitate the burst neurons in contributing to muscle spasm mechanisms following SCI.

Spontaneous firing rate of neurones in the prefrontal cortex of the rat: evidence for a dopaminergic inhibition

1976 ◽  
Vol 116 (3) ◽  
pp. 516-522 ◽  
Author(s):  
F. Mora ◽  
K.F. Sweeney ◽  
E.T. Rolls ◽  
A.M. Sanguinetti
Keyword(s):  
Prefrontal Cortex ◽  
Firing Rate ◽  
Spontaneous Firing ◽  
Spontaneous Firing Rate

Neurodepressing Hormone (Ndh): Fact or Fiction?

Crustaceana ◽  
1996 ◽  
Vol 69 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Alberto Huberman
Keyword(s):  
Molecular Weight ◽  
Firing Rate ◽  
Low Molecular Weight ◽  
Spontaneous Firing ◽  
Sinus Gland ◽  
Spontaneous Firing Rate

AbstractExtracts of the crustacean eyestalk, and particularly of the sinus gland, produce an inhibition of the spontaneous firing rate of motor and sensitive neurons in two different bioassays. This activity can be ascribed to a molecule of low molecular weight, neutral, non-peptidic, soluble in water and methanol, thermostable, different from GABA but suppressed by picrotoxin. Its nature remains to be elucidated.

scholarly journals Regulation of Neuronal Function by Choline and 4OH-GTS-21 Through α7 Nicotinic Receptors

2003 ◽  
Vol 89 (4) ◽  
pp. 1797-1806 ◽  
Author(s):  
Vladimir V. Uteshev ◽  
Edwin M. Meyer ◽  
Roger L. Papke
Keyword(s):  
Firing Rate ◽  
Direct Action ◽  
Choline Uptake ◽  
Spontaneous Firing ◽  
Α7 Nicotinic Acetylcholine Receptor ◽  
Physiological Concentration ◽  
Α7 Nachr ◽  
Synaptic Functions ◽  
Neuronal Functions ◽  
Spontaneous Firing Rate

A unique feature of α7 nicotinic acetylcholine receptor physiology is that, under normal physiological conditions, α7 receptors are constantly perfused with their natural selective agonist, choline. Studying neurons of hypothalamic tuberomammillary (TM) nucleus, we show that choline and the selective α7 receptor agonist 4OH-GTS-21 can regulate neuronal functions directly, via activation of the native α7 receptors, and indirectly, via desensitizing those receptors or transferring them into a state “primed” for desensitization. The direct action produces depolarization and thereby increases the TM neuron spontaneous firing (SF) rate. The regulation of the spontaneous firing rate is robust in a nonphysiological range of choline concentrations >200 μM. However, modest effects persist at concentrations of choline that are likely to be attained perineuronally under some conditions (20–100 μM). At high physiological concentration levels, the indirect choline action reduces or even eliminates the responsiveness of α7 receptors and their availability to other strong cholinergic inputs. Similarly to choline, 4OH-GTS-21 increases the TM neuron spontaneous firing rate via activation of α7 receptors, and this regulation is robust in the range of clinically relevant concentrations of 4OH-GTS-21. We conclude that factors that regulate choline accumulation in the brain and in experimental slices such as choline uptake, hydrolysis of ACh, membrane phosphatidylcholine catabolism, and solution perfusion rate influence α7 nAChR neuronal and synaptic functions, especially under pathological conditions such as stroke, seizures, Alzheimer's disease, and head trauma, when the choline concentration in the CSF is expected to rise.

Spontaneous firing in primary afferent neurons of ampullary electroreceptor organs as attribute of bandwidth, threshold, and topology

2008 ◽  
Vol 58 (3) ◽  
pp. 301-312
Author(s):  
Franklin Bretschneider ◽  
Robert Peters ◽  
Lonneke Eeuwes
Keyword(s):  
Firing Rate ◽  
Carrier Frequency ◽  
Signal To Noise Ratio ◽  
Phase Locking ◽  
Spontaneous Firing ◽  
Sensory Stimuli ◽  
Firing Rates ◽  
Coefficients Of Variation ◽  
Electrical Stimuli ◽  
Spontaneous Firing Rate

AbstractSpontaneous firing of neurons plays an essential part in the detection of sensory stimuli. Spontaneous firing of primary afferents of ampullary electroreceptor organs in the catfish Ameiurus nebulosus (Lesueur, 1819) was studied in relation to the distribution, thresholds, and frequency characteristics of the electroreceptor organs. The spontaneous firing rate was correlated with the place on the skin. The mean inter-spike interval in 55 dorsal and 49 ventral ampullary organs in five specimens was 16.8 ms +/- 0.41 SEM and 20.5 ms +/- 0.48 SEM, corresponding to firing rates of 59.5 and 48.7 s-1 respectively. The concomitant coefficients of variation were 0.33 and 0.29. Approximately half of the dorsal ampullae were innervated by two fibres. The firing rates of each of the two fibres was lower than the firing rate of organs innervated by a single neuron. Responses to stimuli as weak as 10 pA could be recovered from the noisy average firing level provided the number of averaging sweeps was sufficiently large. This was equivalent to a stimulus of 0.025 μV/cm and was lower than the behavioural threshold of 1 μV/cm. The gain of the frequency response was enhanced at the carrier frequency, at twice the carrier frequency, and in the range from 75-90 Hz. The results revealed that the occurrence of spontaneous activity improved the signal to noise ratio of responses to electrical stimuli by reduction of the coefficient of variation, absence of a threshold, and phase locking.

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