Biomaterial Database

Projections from upper cervical inspiratory neurons to thoracic and lumbar expiratory motor nuclei in the cat. 1988

R W Hoskin, and L M Fedorko, and J Duffin

Department of Anaesthesia, University of Toronto, Ontario, Canada.

Previous studies have demonstrated the existence of axonal projections from propriospinal respiratory neurons in the rostral cervical cord of the cat (upper cervical inspiratory neurons) to the vicinity of the phrenic and rostral thoracic inspiratory (external) intercostal motoneurons. However, no synaptic targets of the upper cervical inspiratory neurons have been identified. This study investigated the axonal projections to the caudal thoracic and upper lumbar cord and the possible existence of inhibitory connections to the expiratory intercostal and abdominal motoneurons. The connections from upper cervical inspiratory neurons to expiratory motoneurons in the lower thoracic cord were examined using the methods of antidromic mapping and the spike-triggered averaging of intracellular potentials. Of the 70 upper cervical inspiratory neurons examined, only four (5.7%) could not be antidromically activated from the T9 segment of the spinal cord. The axons of 66 upper cervical inspiratory antidromic activation at less than 5 microV, and the presence of collaterals was confirmed by antidromic mapping in 30 cases (49.2%). Of 21 axons tested for lumbar projections, 13 (61.9%) projected as far as T12, seven (33.3%) as far as L1, three (14.3%) as far as L2, and one (4.8%) was antidromically activated from L3. Spike-triggered averaging of the synaptic potentials recorded intracellularly from expiratory intercostal motoneurons in T9 and T10 spinal segments was done for 27 upper cervical inspiratory neurons, 17 of these with 4 or more motoneurons, for a total of 111 expiratory motoneurons. In 16 cases the motoneurons were injected with Cl- to reverse IPSPs and the spike-triggered averaging was repeated. No monosynaptic or disynaptic post-synaptic potentials were seen in any of the spike-triggered averages. We concluded that the upper cervical inspiratory neurons may provide inspiratory inhibition to expiratory motoneurons via a di- or oligosynaptic pathway involving segmental inhibitory interneurons and that either the spike-triggered averaging technique was not sensitive enough to detect the ipsilateral connections or the interneuron pathway was to the contralateral side of the spinal cord.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009434	Neural Pathways	Neural tracts connecting one part of the nervous system with another.	Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, 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
D012119	Respiration	The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (	Breathing
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
D005260	Female		Females
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
D013116	Spinal Cord	A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.	Coccygeal Cord,Conus Medullaris,Conus Terminalis,Lumbar Cord,Medulla Spinalis,Myelon,Sacral Cord,Thoracic Cord,Coccygeal Cords,Conus Medullari,Conus Terminali,Cord, Coccygeal,Cord, Lumbar,Cord, Sacral,Cord, Spinal,Cord, Thoracic,Cords, Coccygeal,Cords, Lumbar,Cords, Sacral,Cords, Spinal,Cords, Thoracic,Lumbar Cords,Medulla Spinali,Medullari, Conus,Medullaris, Conus,Myelons,Sacral Cords,Spinal Cords,Spinali, Medulla,Spinalis, Medulla,Terminali, Conus,Terminalis, Conus,Thoracic Cords
D013909	Thorax	The upper part of the trunk between the NECK and the ABDOMEN. It contains the chief organs of the circulatory and respiratory systems. (From Stedman, 25th ed)	Chest,Thoraces,Chests,Thorace