Sensory Neurons: Simulations of Experiments on Single Nerve Fibers and Brain Cells of Sensory Systems. Version 1.0.Richard R. Fay

1993 ◽  
Vol 68 (3) ◽  
pp. 482-483
Author(s):  
Gary R. Lewin
Keyword(s):  
Sensory Neurons ◽  
Sensory Systems ◽  
Nerve Fibers ◽  
Brain Cells ◽  
Single Nerve

Projections from sensory neurons developing at ectopic sites in insects

Development ◽  
1981 ◽  
Vol 65 (Supplement) ◽  
pp. 209-224
Author(s):  
Hilary Anderson
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sensory Neurons ◽  
Sensory Systems ◽  
Genetic Mutation ◽  
Detailed Understanding ◽  
Giant Interneuron ◽  
The Central Nervous System ◽  
Ectopic Neurons

This paper reviews recent experiments which attempt to gain more understanding about the recognition processes involved in the formation of neuronal connexions by studying the degree of specificity with which sensory neurons form their central connexions. This is done by generating ectopic neurons (either by transplantation or by genetic mutation) whose axons grow into novel regions of the central nervous system, and then examining their projections and synapses. The sensory systems reviewed are: the Antennapedia, spineless-aristapedia, proboscipedia, and bithorax homeotic mutants of Drosphila melanogaster; the cercus-to-giant interneuron system of crickets, and the wind-sensitive hair system of locusts. The results show that ectopic neurons form projections that are discrete and characteristic, not random and chaotic. In those cases where single classes of sensilla have been studied, they follow either their normal CNS pathways or those pathways normally used by their segmental homologues. Ectopic sensory neurons can also form appropriate functional connexions in some cases but not in others. Possible reasons are discussed, but detailed understanding of the underlying events requires further experimentation.

Iodoacetate depression in Xenopus sciatic single nerve fibers

1965 ◽  
Vol 208 (4) ◽  
pp. 720-723 ◽  
Author(s):  
Gordon M. Schoepfle ◽  
Eliska Atkins ◽  
Larry A. Schafer
Keyword(s):  
Membrane Potential ◽  
Maximum Rate ◽  
Nerve Fibers ◽  
Rate Of Change ◽  
Resting Membrane Potential ◽  
Delayed Effect ◽  
Fluid Exchange ◽  
Sodium Conductance ◽  
Single Nerve ◽  
A Chain

Under conditions of continuous fluid exchange at a pH 7.55, a 10-min exposure of Xenopus sciatic single nerve fibers to iodoacetate results in eventual decline in the maximum rate of change of membrane potential, even after a delay of an hour or more during which no changes are apparent. This delayed effect is obtained over an iodoacetate concentration range of 0.1–20.0 mm sodium iodoacetate. Neither the resting membrane potential nor the maximal limiting response obtained during hyperpolarization are affected at a time when iodoacetate has appreciably depressed the spike in the nonpolarized fiber. These findings are taken to indicate that iodoacetate blocks a chain of reactions at a link remote from the process directly concerned with maintenance of the resting level of the sodium conductance. Neither lactate nor pyruvate can be relied on to bring about recovery from the iodoacetate depression.

An intracellular study of chemosensory fibers and endings

1980 ◽  
Vol 44 (6) ◽  
pp. 1077-1088 ◽  
Author(s):  
Y. Hayashida ◽  
H. Koyano ◽  
C. Eyzaguirre
Keyword(s):  
Carotid Body ◽  
Action Potentials ◽  
Physiological Saline ◽  
Mean Amplitude ◽  
Nerve Fibers ◽  
Chemical Stimulation ◽  
Nerve Terminals ◽  
Generator Potential ◽  
Single Nerve ◽  
Frequency Changes

1. The carotid body and its nerve, removed from anesthetized cats, were placed in physiological saline flowing under paraffin oil. The nerve, lifted into the oil, was used for either electrical stimulation or recording of the total afferent discharge. Intracellular recordings were obtained from individual nerve fibers and endings within the carotid body. The recording sites were identified by injecting Procion yellow through the intracellular electrodes; the tissues were then prepared for histology and observed with episcopic fluorescence or Nomarski optics. 2. Intracellularly recorded chemosensory fibers conducted at 1.1-30 m/s and usually displayed action potentials of regular amplitude. At times, however, some spikes become partially blocked while others maintained their original amplitude. "Natural" (hypoxia) or chemical (ACh or NaCN) stimulation induced different patterns of frequency changes of the large and small action potentials. This indicated nerve fiber branching at some distance from the recording site. 3. Intra- and extracellularly recorded spikes were blocked in 0 [Na+]0 by tetrodotoxin (TTX) or procaine. 4. During chemical stimulation, a slowly occurring depolarization (receptor or generator potential) was recorded intracellularly from the afferent fibers. It developed concomitantly with the increase in discharge. 5. Impalement of single nerve terminals (histologically identified) showed numerous "spontaneous" depolarizing potentials (SDPs) that had a mean amplitude of 5.6 mV, a mean duration of 46.1 ms, and nearly random distribution. They increased in frequency and summated during chemical stimulation. SDPs originated from either the site of recording or from neighboring areas. When the SDPs attained a certain amplitude, they seemed to give rise to action potentials. Also, relatively well developed or partially blocked spikes (apparently originating elsewhere) were recorded from single nerve terminals. 6. The receptor (generator) potential of chemosensory receptors appears to be an integrated response formed by multiple activity originating in different nerve endings.

Hypoglycemic detection at the portal vein is mediated by capsaicin-sensitive primary sensory neurons

2007 ◽  
Vol 293 (1) ◽  
pp. E96-E101 ◽  
Author(s):  
Satoshi Fujita ◽  
MaryAnn Bohland ◽  
Graciela Sanchez-Watts ◽  
Alan G. Watts ◽  
Casey M. Donovan
Keyword(s):  
Portal Vein ◽  
Sensory Neurons ◽  
Jugular Vein ◽  
Immunohistochemical Analysis ◽  
Nerve Fibers ◽  
Similar Response ◽  
Primary Sensory Neurons ◽  
Calcitonin Gene ◽  
Epinephrine Concentration

To elucidate the type of spinal afferent involved in hypoglycemic detection at the portal vein, we considered the potential role of capsaicin-sensitive primary sensory neurons. Specifically, we examined the effect of capsaicin-induced ablation of portal vein afferents on the sympathoadrenal response to hypoglycemia. Under anesthesia, the portal vein was isolated in rats and either capsaicin (CAP) or the vehicle (CON) solution applied topically. During the same surgery, the carotid artery (sampling) and jugular vein (infusion) were cannulated. One week later, all animals underwent a hyperinsulinemic hypoglycemic clamp, with glucose (variable) and insulin (25 mU·kg−1·min−1) infused via the jugular vein. Systemic hypoglycemia (2.76 ± 0.05 mM) was induced by minute 75 and sustained until minute 105. By design, no significant differences were observed in arterial glucose or insulin concentrations between groups. When hypoglycemia was induced in CON, the plasma epinephrine concentration increased from 0.67 ± 0.05 nM at basal to 36.15 ± 2.32 nM by minute 105. Compared with CON, CAP animals demonstrated an 80% suppression in epinephrine levels by minute 105, 7.11 ± 0.55 nM ( P < 0.001). A similar response to hypoglycemia was observed for norepinephrine, with CAP values suppressed by 48% compared with CON. Immunohistochemical analysis of the portal vein revealed an 85% decrease in the number of calcitonin gene-related peptide-reactive nerve fibers following capsaicin-induced ablation. That the suppression in the sympathoadrenal response was comparable to our previous findings for total denervation of the portal vein indicates that hypoglycemic detection at the portal vein is mediated by capsaicin-sensitive primary sensory neurons.

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