Biomaterial Database

An EM study of the dorsal nucleus of the lateral lemniscus: inhibitory, commissural, synaptic connections between ascending auditory pathways. 1989

D L Oliver, and A Shneiderman

Department of Anatomy, University of Connecticut Health Center, Farmington 06032.

The dorsal nucleus of the lateral lemniscus (DNLL) and its connections constitute one of the ascending auditory pathways to the inferior colliculus. One notable feature of this nucleus is the heavy commissural connections between DNLL on opposite sides of the midbrain. These commissural connections may have a significant impact on the ascending pathway. In this study, the fine structure of DNLL in the cat and its commissural connections were examined. Both anterograde and retrograde transport methods were used simultaneously at the EM level. Injections of 3H-leucine mixed with WGA-HRP were made in one DNLL. After axonal transport, EM autoradiographic methods were used to identify the anterogradely labeled axonal endings from the opposite DNLL. In the same location, retrogradely labeled neurons with crossed connections were identified with HRP histochemistry. Two types of axonal endings were found in DNLL, those with round synaptic vesicles forming asymmetrical synaptic junctions and those with pleomorphic vesicles and symmetrical synapses. Both types were equally common. However, only endings with pleomorphic vesicles were labeled after injections in the contralateral DNLL. The labeled endings from the opposite DNLL appeared to represent a homogeneous population, even though a number of variations in the 2 types of endings were found. Labeled endings were presynaptic to all parts of neurons in DNLL, but a large proportion of the synapses were on cell bodies and large dendrites. Two patterns of nuclear morphology and distribution of rough endoplasmic reticulum were identified and may represent different cell types. Examples of both cell types were observed to project to the contralateral side and received labeled synaptic endings. The major finding of this study is that the crossed connections between DNLL exhibit the morphology associated with inhibitory function. Since neurons in DNLL are thought to use GABA as a neurotransmitter, the crossed connections could provide inhibitory inputs to DNLL on each side. Since some neurons receive numerous axosomatic inputs from the contralateral DNLL and also project to the opposite side, they may participate in direct reciprocal, inhibitory connections between the nuclei. Crossed inhibitory connections in the DNLL pathway may be important in regulating the flow of ascending auditory information.

UI	MeSH Term	Description	Entries
D007245	Inferior Colliculi	The posterior pair of the quadrigeminal bodies which contain centers for auditory function.	Colliculus, Inferior,Brachial Nucleus of the Inferior Colliculus,Caudal Colliculus,Colliculus Inferior,Inferior Colliculus,Posterior Colliculus,Colliculi, Inferior,Colliculus Inferiors,Colliculus, Caudal,Colliculus, Posterior,Inferior, Colliculus,Inferiors, Colliculus
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009433	Neural Inhibition	The function of opposing or restraining the excitation of neurons or their target excitable cells.	Inhibition, Neural
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D003712	Dendrites	Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.	Dendrite
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
D001306	Auditory Pathways	NEURAL PATHWAYS and connections within the CENTRAL NERVOUS SYSTEM, beginning at the hair cells of the ORGAN OF CORTI, continuing along the eighth cranial nerve, and terminating at the AUDITORY CORTEX.	Auditory Pathway,Pathway, Auditory,Pathways, Auditory
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse