Deafferentation slows the growth of specific dendrites of identified giant interneurons

1975 ◽  
Vol 159 (3) ◽  
pp. 407-418 ◽  
Author(s):  
R. K. Murphey ◽  
Barbara Mendenhall ◽  
J. Palka ◽  
J. S. Edwards
Keyword(s):  
Giant Interneurons

Independent Coding of Wind Direction in Cockroach Giant Interneurons

1997 ◽  
Vol 78 (5) ◽  
pp. 2655-2661 ◽  
Author(s):  
Adi Mizrahi ◽  
Frederic Libersat
Keyword(s):  
Sensory Processing ◽  
Wind Direction ◽  
Information Transfer ◽  
Cell Interactions ◽  
Synaptic Activity ◽  
Cercal System ◽  
Giant Interneurons ◽  
Before And After ◽  
Left And Right

Mizrahi, Adi and Frederic Libersat. Independent coding of wind direction in cockroach giant interneurons. J. Neurophysiol. 78: 2655–2661, 1997. In this study we examined the possible role of cell-to-cell interactions in the localization processing of a wind stimulus by the cockroach cercal system. Such sensory processing is performed primarily by pairs of giant interneurons (GIs), a group of highly directional cells. We have studied possible interactions among these GIs by comparing the wind sensitivity of a given GI before and after removing another GI with the use of photoablation. Testing various combinations of GI pairs did not reveal any suprathreshold interactions. This was true for all unilateral GI pairs on the left or right side as well as all the bilateral GI pairs (left and right homologues). Those experiments in which we were able to measure synaptic activity did not reveal subthreshold interactions between the GIs either. We conclude that the GIs code independently for a given wind direction without local GI–GI interactions. We discuss the possible implications of the absence of local interactions on information transfer in the first station of the escape circuit.

Tachykinin-mediated modulation of sensory neurons, interneurons, and synaptic transmission in the lamprey spinal cord

1996 ◽  
Vol 76 (6) ◽  
pp. 4031-4039 ◽  
Author(s):  
D. Parker ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Substance P ◽  
Synaptic Transmission ◽  
Dorsal Root ◽  
Input Resistance ◽  
Dorsal Column ◽  
Giant Interneurons ◽  
Potassium Conductances ◽  
Dorsal Cells ◽  
Measurable Change

1. Tachykinin-like immunoreactivity is found in the dorsal roots, dorsal horn, and dorsal column of the lamprey. The effect of tachykinins on sensory processing was examined by recording intracellularly from primary sensory dorsal cells and second-order spinobulbar giant interneurons. Modulation of synaptic transmission was examined by making paired recordings from dorsal cells and giant interneurons, or by eliciting compound depolarizations in the giant interneurons by stimulating the dorsal root or dorsal column. 2. Bath application of tachykinins depolarized the dorsal cells. This effect was mimicked by stimulation of the dorsal root, suggesting that dorsal root afferents may be a source of endogenous tachykinin input to the spinal cord. The depolarization was reduced by removal of sodium or calcium from the Ringer, or when potassium conductances were blocked, and was not associated with a measurable change in input resistance. Dorsal root stimulation also caused a depolarization in the dorsal cells, and this effect and that of bath-applied substance P, was blocked by the tachykinin antagonist spantide. 3. The tachykinin substance P could reduce inward and outward rectification in the dorsal cells, the effect on outward rectification only being seen when potassium conductances were blocked by tetraethylammonium (TEA). 4. Substance P increased the excitability of the dorsal cells and giant interneurons, shown by the increased spiking in response to depolarizing current pulses. The increased excitability was blocked by the tachykinin antagonist spantide. 5. Substance P modulated the dorsal cell action potential, by increasing the spike duration and reducing the amplitude of the afterhyperpolarization. The spike amplitude was not consistently affected. 6. Stimulation of the dorsal column resulted in either depolarizing or hyperpolarizing potentials in the giant interneurons. The amplitude of the depolarization was increased by substance P, whereas the amplitude of the hyperpolarization was reduced. These effects occurred independently of a measurable change in postsynaptic input resistance, suggesting that the modulation occurred presynaptically. Paired recordings from dorsal cells and giant interneurons failed to reveal an effect of substance P on dorsal cell-evoked excitatory postsynaptic potentials (EPSPs), suggesting that the potentiation of the dorsal column-evoked depolarization was due to an effect on other axons in the dorsal column. Dorsal root-evoked potentials could also be increased in the presence of substance P, although this effect was less consistent than the effect on dorsal column stimulation. 7. These results suggest that tachykinins modulate sensory input to the lamprey spinal cord by increasing the excitability of primary afferents and second-order giant interneurons, and also by modulating synaptic transmission. Tachykinins may result in potentiation of local spinal reflexes and also modulation of descending reticulospinal inputs to the spinal locomotor network as a result of potentiation of spinobulbar inputs.

Sign in / Sign up

Export Citation Format

Share Document