Biomaterial Database

Spinal pathways mediating tonic or stimulation-produced descending inhibition from the periaqueductal gray or nucleus raphe magnus are separate in the cat. 1987

J Sandkühler, and Q G Fu, and M Zimmermann

II. Physiologisches Institut, Universität Heidelberg, West Germany.

1. The spinal pathways for tonic and stimulation-produced descending inhibition of spinal nociceptive neurons were investigated in anesthetized paralyzed cats. Reversible circumscribed blocks were produced at various depths in the lateral funiculi (LF) at L1-L2 using the microinjection of the local anesthetic lidocaine. The total amount of tonic descending inhibition in the absence of LF blocks was evaluated by monitoring the spinal neuronal activity during reversible spinalization by cold block and compared with the activity of the same neuron during LF blocks. Stimulation-induced descending inhibition of neuronal responses to noxious skin heating was produced by bipolar focal electrical stimulation in the periaqueductal gray (PAG) or nucleus raphe magnus (NRM) and compared with the inhibition of the same neurons during LF blocks. The relative significance of ipsi- and contralateral pathways in the dorsal, medial, or ventral aspects of the lateral funiculi for these types of descending inhibition are quantitatively described. 2. All 35 lumbar spinal dorsal horn neurons studied responded to noxious and innocuous mechanical and noxious thermal stimuli applied within the receptive fields on the glabrous skin of the hindlimb. Responses to noxious skin stimuli (50 degrees C, 10 s at 3-min intervals) were constant over time and served as a parameter to evaluate tonic and stimulation-produced descending inhibition. All neurons also responded to electrical stimulation of hindlimb cutaneous nerves supramaximal for the activation of A-beta-, delta-, and C-fibers. Neurons were located in laminae I-VI of the dorsal horn at L5-L7 levels. LF blocks were produced by the microinjection of 1 microliter lidocaine at each of one to six sites in the ipsilateral and/or contralateral LF 500, 1,500, and/or 2,500 microns below cord surface. 3. LF blocks ipsilateral to the recording sites in the cord significantly reduced tonic inhibition, with blocks in the dorsal part of the LF [i.e., the dorsolateral funiculus (DLF)] being equally effective to complete LF blocks. Stimulation-produced inhibition from PAG or NRM was, however, not significantly affected by ipsilateral LF blocks. 4. Contralateral LF blocks significantly reduced stimulation-produced descending inhibition and failed to affect tonic descending inhibition. Ventral LF blocks attenuated inhibition from the PAG but not from NRM, whereas DLF blocks were more effective on inhibition from the NRM. 5. Bilateral LF blocks significantly reduced tonic as well as stimulation-produced descending inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007839	Functional Laterality	Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.	Ambidexterity,Behavioral Laterality,Handedness,Laterality of Motor Control,Mirror Writing,Laterality, Behavioral,Laterality, Functional,Mirror Writings,Motor Control Laterality,Writing, Mirror,Writings, Mirror
D009433	Neural Inhibition	The function of opposing or restraining the excitation of neurons or their target excitable cells.	Inhibition, Neural
D009475	Neurons, Afferent	Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.	Afferent Neurons,Afferent Neuron,Neuron, Afferent
D010146	Pain	An unpleasant sensation induced by noxious stimuli which are detected by NERVE ENDINGS of NOCICEPTIVE NEURONS.	Suffering, Physical,Ache,Pain, Burning,Pain, Crushing,Pain, Migratory,Pain, Radiating,Pain, Splitting,Aches,Burning Pain,Burning Pains,Crushing Pain,Crushing Pains,Migratory Pain,Migratory Pains,Pains, Burning,Pains, Crushing,Pains, Migratory,Pains, Radiating,Pains, Splitting,Physical Suffering,Physical Sufferings,Radiating Pain,Radiating Pains,Splitting Pain,Splitting Pains,Sufferings, Physical
D010487	Periaqueductal Gray	Central gray matter surrounding the CEREBRAL AQUEDUCT in the MESENCEPHALON. Physiologically it is probably involved in RAGE reactions, the LORDOSIS REFLEX; FEEDING responses, bladder tonus, and pain.	Mesencephalic Central Gray,Midbrain Central Gray,Central Gray Substance of Midbrain,Central Periaqueductal Gray,Griseum Centrale,Griseum Centrale Mesencephali,Periaqueductal Gray Matter,Substantia Grisea Centralis,Substantia Grisea Centralis Mesencephali,Central Gray, Mesencephalic,Central Gray, Midbrain,Gray Matter, Periaqueductal,Gray, Central Periaqueductal,Griseum Centrale Mesencephalus,Periaqueductal Grays, Central
D011903	Raphe Nuclei	Collections of small neurons centrally scattered among many fibers from the level of the TROCHLEAR NUCLEUS in the midbrain to the hypoglossal area in the MEDULLA OBLONGATA.	Caudal Linear Nucleus of the Raphe,Interfascicular Nucleus,Nucleus Incertus,Rostral Linear Nucleus of Raphe,Rostral Linear Nucleus of the Raphe,Superior Central Nucleus,Central Nucleus, Superior,Incertus, Nucleus,Nuclei, Raphe,Nucleus, Interfascicular,Nucleus, Raphe,Nucleus, Superior Central,Raphe Nucleus
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
D004525	Efferent Pathways	Nerve structures through which impulses are conducted from a nerve center toward a peripheral site. Such impulses are conducted via efferent neurons (NEURONS, EFFERENT), such as MOTOR NEURONS, autonomic neurons, and hypophyseal neurons.	Motor Pathways,Efferent Pathway,Pathway, Efferent,Pathways, Efferent
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D005260	Female		Females