Biomaterial Database

Nigral inhibitory termination on efferent neurons of the superior colliculus: an intracellular horseradish peroxidase study in the cat. 1985

A B Karabelas, and A K Moschovakis

Intracellularly recorded responses of deeper tectal neurons to stimulation of the substantia nigra and the cerebral peduncle were obtained to demonstrate the monosynaptic inhibitory nature of the nigrotectal pathway in the cat. We also employed antidromic stimulation (contralateral predorsal bundle and superior colliculus) and intracellular labeling with HRP to demonstrate which types of tectal efferent neurons are nigrorecipient. The response to nigral stimulation in 61% of the cells studied was a monosynaptic IPSP of short duration. Recovered HRP-labeled nigrorecipient neurons include X1 (large multipolar radiating), X2 (tufted), X4 (medium-size vertical), X5 (medium-size horizontal), T1 (medium-size trapezoid radiating), T2 (small ovoid vertical), I (small sparsely ramified), and A (small horizontal) neurons. Nigrorecipient cells participate in all four of the major efferent axonal systems of the deeper tectal layers: crossed descending (X and T neurons), ipsilateral descending (I and T neurons), ascending (A, X, and T neurons), and commissural (T neurons). EPSPs accompanied by long-lasting hyperpolarizing potentials were recorded from the remaining tectal neurons in response to stimulation of the substantia nigra, cerebral peduncle, and pericruciate cortex. Collision experiments indicate that at least part of the excitatory responses of tectal neurons to nigral and penduncular stimulation are mediated by corticotectal fibers traversing the cerebral peduncle and the substantia nigra. Excitatory effects of nigral, peduncular, and cortical stimulation were disclosed in X neurons including the non-nigrorecipient large vertical neurons of the X3 subgroup. Cortical excitatory and nigral inhibitory inputs converge only on X neurons (X1, X2, X4, X5). In this case, nigrally evoked IPSPs were preceded by a brief EPSP. Collectively, these results demonstrate the inhibitory termination of the nigrotectal pathway on a wide variety of deeper tectal efferent neurons. Such findings imply the versatility of the nigral involvement in tectal mechanisms of gaze control. We suggest that the substantia nigra pars reticulata contacts tectal neurons differing as to their response properties and shapes the signal carried by all the major tectofugal bundles.

UI	MeSH Term	Description	Entries
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
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
D001931	Brain Mapping	Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.	Brain Electrical Activity Mapping,Functional Cerebral Localization,Topographic Brain Mapping,Brain Mapping, Topographic,Functional Cerebral Localizations,Mapping, Brain,Mapping, Topographic Brain
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
D002540	Cerebral Cortex	The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulci. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.	Allocortex,Archipallium,Cortex Cerebri,Cortical Plate,Paleocortex,Periallocortex,Allocortices,Archipalliums,Cerebral Cortices,Cortex Cerebrus,Cortex, Cerebral,Cortical Plates,Paleocortices,Periallocortices,Plate, Cortical
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
D012438	Saccades	An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.	Pursuit, Saccadic,Saccadic Eye Movements,Eye Movement, Saccadic,Eye Movements, Saccadic,Movement, Saccadic Eye,Movements, Saccadic Eye,Pursuits, Saccadic,Saccade,Saccadic Eye Movement,Saccadic Pursuit,Saccadic Pursuits
D013378	Substantia Nigra	The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce DOPAMINE, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored MELANIN is a by-product of dopamine synthesis.	Nigra, Substantia,Nigras, Substantia,Substantia Nigras
D013477	Superior Colliculi	The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.	Colliculus, Superior,Optic Lobe, Human,Optic Lobe, Mammalian,Optic Tectum,Anterior Colliculus,Superior Colliculus,Tectum, Optic,Colliculi, Superior,Colliculus, Anterior,Human Optic Lobe,Human Optic Lobes,Mammalian Optic Lobe,Mammalian Optic Lobes,Optic Lobes, Human,Optic Lobes, Mammalian,Optic Tectums,Tectums, Optic