Biomaterial Database

Presynaptic inhibition in the crayfish CNS: pathways and synaptic mechanisms. 1985

M D Kirk

I studied the pathways that produce primary afferent depolarization (PAD) and presynaptic inhibition during crayfish escape behavior. Simultaneous intracellular recordings were obtained from interneurons and primary afferent axons in the neuropil of the sixth abdominal ganglion. In several experiments, a sucrose-gap recording of PAD accompanied the intracellular impalements. I have identified PAD-producing inhibitory interneurons (PADIs) that are fired by a single impulse in the lateral (LG) or medial (MG) giant, escape-command axons; the PADIs appear to be directly responsible for presynaptic inhibition of primary afferent input to identified mechanosensory interneurons. PADI spikes, elicited by injection of depolarizing current, produced unitary PAD with constant short latency (mean = 0.97 +/- 0.12 SD ms). The unitary PADs were capable of following PADI impulses one for one at frequencies greater than 100 Hz, and the amplitude of unitary PAD was increased by injection of chloride into the afferent terminals. Therefore, the PADIs appear to directly produce an increase in chloride conductance in the primary afferent terminals. Intracellular injections of Lucifer yellow or horseradish peroxidase (HRP) revealed three morphological types of PADI. Their axonal branches and terminals are bilateral and overlap extensively with the innervation fields of all 10 sensory roots of the sixth ganglion. The three morphological types of PADI were physiologically indistinguishable. In several cases, the impaled PADI was shown to produce unitary PAD in more than one afferent of a given root as well as in afferents of adjacent roots. Therefore, the PADIs appear to diverge widely and contact many afferents in all of the sixth-ganglion sensory roots. Stimulation, caudal to the fifth ganglion, of an MG that had been interrupted rostral to the fifth ganglion produced no PAD in sixth-ganglion afferents. Also, stimulation of an MG or an LG in a surgically isolated sixth abdominal ganglion failed to produce PAD. Therefore, the pathway between the MGs and PADIs is activated exclusively within the rostral abdominal ganglia. Direct stimulation in the second and third abdominal ganglia of the segmental giants (SGs) produced a polysynaptic, suprathreshold response in the PADIs. This response was compound and was not due to the activity of the identified corollary discharge interneurons, CDI-2 and CDI-3, that are fired by the SGs. Therefore, the primary input to the PADIs must come from other, unidentified CDIs that are driven by the SGs. PADIs were not fired by shocks to the sensory portions of any peripheral roots even though these shocks produced PAD.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007395	Interneurons	Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.	Intercalated Neurons,Intercalated Neuron,Interneuron,Neuron, Intercalated,Neurons, Intercalated
D008297	Male		Males
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009433	Neural Inhibition	The function of opposing or restraining the excitation of neurons or their target excitable cells.	Inhibition, Neural
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D003400	Astacoidea	A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.	Astacus,Crayfish,Procambarus,Astacoideas,Crayfishs
D005260	Female		Females
D005724	Ganglia	Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon