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Morphophysiology of neurons of the rat ventrobasal thalamic complex. An intracellular HRP study
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SPINAL PROJECTIONS TO MIDBRAIN IN CAT M BjSrke]and* and ~ . . . . . • " . 255 Po J. Boivie, Dept of Anatomy, Karolinska Instltute, Stockholm~ T h u r s d a y and Dept of Neurology,University Hospital,Uppsala,Sweden. [ Experimental animal studies as well as observations in man indicate that some parts of the mesencepha][c reticular formation (MRF) and the periaqueductal gray substance (PAG) play a role in pain. These regions receive direct projections from the spinal cord. In the present anatomical investigation the exact pattern of termination of these projections have been studied in cat. The results are based mainly on degeneration experiments with spinal cord lesions in adult cats. All lesions were made caudal to the lateral cervical nucleus. Additional experiments using orthograde transport of horseradish peroxidase(HRP) support the results from the degeneration experiments. Few spinal fibers terminate in the ventral half of the midbrain, but in its dorsal half extensive terminal fiber networks are found at all rostrocaudal levels. A continuous terminal zone extends from the caudal to the rostral end of PAG, in which the degeneration was densest caudal to the superior colliculus. Other terminal zones include the external nucleus of the inferior colliculus, cuneiforme nucleus, superior colliculus and posterior pretectal nucleus. Some other, more vaguely defined parts of MRF receive a scattered projection. After strictly unilateral lesions only few degenerating fibers were found contralaterally. The extensive spinal projections to the midbrain demonstrated in this and previous anatomical studies support the notion that several midbrain regions are important for somesthetic functions, including pain. Further indications of this are found in the fact that also the lateral cervical nucleus and dorsal column nuclei project extensively to the midbrain. (Supported by Swedish Medical Research Council project 3391). MORPHOPHYSIOLOGY OF NEURONS OF THE RAT VENTROBASAL THALAMIC 256 Po COMPLEX. AN INTRACELLULAR HRP STUDY. C.L. Lee, I, Thursday H. Peschanski,l,2, and H.J. Ralston III, i, Dept. of Anat., Univ. Calif., San Francisco, CA 94143, USA, Unite Inserm U 16], 2 rue d'Al~sia, Paris France In the ventrobasal thalamic complex of the rat, numerous neurons responding to noxious stimuli (N) have been recorded, intermingled with cells presenting classical "lemniscal-type" responses to non-noxious stimuli (Nn). This study has been undertaken to determine whether morphological differences could be found between these two kinds of cells. Electrodes filled with HRP (lO~) in .05M Tris buffer (pH 7.6) and KCI (.bM) were used. Neurons were usually characterized extracellularly with somatic noxious and non-noxious cutaneous stimuli. Then a current pulse was used to impale the cell, intracellular response was checked and HRP injected (pulses of l0 hA, 6 ms, 150 Hz, 2-5 min). The brain was perfused, vibratomed (75pm thick sections), reacted with DAB and embedded in Epon Araldite. Each injected neuron was morphologically identified and drawn prior to final trimming and thin sectioning for EM study. Compared to Nn cells, N neurons seem to present some particular features. They have more rounded cell bodies ( ~ 20p); the 4 to 6 primary dendrites divide rapidly in large secondary dendrites without tufted organization nor obvious orientation along a main axis; appendages of various sizes and shapes are located along dendrites of all orders, in contrast with Nn neurons whose primary dendrites are free of appendages. These preliminary data seem thus to indicate that "noxious" responsive neurons present particular morphological features. Electron microscopic study of synapses ending on both kind of cells is in progress. Supported by NS I]614 from USPHS
SPINAL PROJECTIONS TO MIDBRAIN IN CAT M BjSrke]and* and ~ . . . . . • " . 255 Po J. Boivie, Dept of Anatomy, Karolinska Instltute, Stockholm~ T h u r s d a y and Dept of Neurology,University Hospital,Uppsala,Sweden. [ Experimental animal studies as well as observations in man indicate that some parts of the mesencepha][c reticular formation (MRF) and the periaqueductal gray substance (PAG) play a role in pain. These regions receive direct projections from the spinal cord. In the present anatomical investigation the exact pattern of termination of these projections have been studied in cat. The results are based mainly on degeneration experiments with spinal cord lesions in adult cats. All lesions were made caudal to the lateral cervical nucleus. Additional experiments using orthograde transport of horseradish peroxidase(HRP) support the results from the degeneration experiments. Few spinal fibers terminate in the ventral half of the midbrain, but in its dorsal half extensive terminal fiber networks are found at all rostrocaudal levels. A continuous terminal zone extends from the caudal to the rostral end of PAG, in which the degeneration was densest caudal to the superior colliculus. Other terminal zones include the external nucleus of the inferior colliculus, cuneiforme nucleus, superior colliculus and posterior pretectal nucleus. Some other, more vaguely defined parts of MRF receive a scattered projection. After strictly unilateral lesions only few degenerating fibers were found contralaterally. The extensive spinal projections to the midbrain demonstrated in this and previous anatomical studies support the notion that several midbrain regions are important for somesthetic functions, including pain. Further indications of this are found in the fact that also the lateral cervical nucleus and dorsal column nuclei project extensively to the midbrain. (Supported by Swedish Medical Research Council project 3391). MORPHOPHYSIOLOGY OF NEURONS OF THE RAT VENTROBASAL THALAMIC 256 Po COMPLEX. AN INTRACELLULAR HRP STUDY. C.L. Lee, I, Thursday H. Peschanski,l,2, and H.J. Ralston III, i, Dept. of Anat., Univ. Calif., San Francisco, CA 94143, USA, Unite Inserm U 16], 2 rue d'Al~sia, Paris France In the ventrobasal thalamic complex of the rat, numerous neurons responding to noxious stimuli (N) have been recorded, intermingled with cells presenting classical "lemniscal-type" responses to non-noxious stimuli (Nn). This study has been undertaken to determine whether morphological differences could be found between these two kinds of cells. Electrodes filled with HRP (lO~) in .05M Tris buffer (pH 7.6) and KCI (.bM) were used. Neurons were usually characterized extracellularly with somatic noxious and non-noxious cutaneous stimuli. Then a current pulse was used to impale the cell, intracellular response was checked and HRP injected (pulses of l0 hA, 6 ms, 150 Hz, 2-5 min). The brain was perfused, vibratomed (75pm thick sections), reacted with DAB and embedded in Epon Araldite. Each injected neuron was morphologically identified and drawn prior to final trimming and thin sectioning for EM study. Compared to Nn cells, N neurons seem to present some particular features. They have more rounded cell bodies ( ~ 20p); the 4 to 6 primary dendrites divide rapidly in large secondary dendrites without tufted organization nor obvious orientation along a main axis; appendages of various sizes and shapes are located along dendrites of all orders, in contrast with Nn neurons whose primary dendrites are free of appendages. These preliminary data seem thus to indicate that "noxious" responsive neurons present particular morphological features. Electron microscopic study of synapses ending on both kind of cells is in progress. Supported by NS I]614 from USPHS