RESPIRATORY SUPPRESSION BY FOCAL COOLING OF VENTRAL MEDULLARY SURFACEIN ANESTHETIZED RATS - FUNCTIONAL AND NEUROANATOMICAL CORRELATE

Bilateral cooling of the parapyramidal region in the rostral ventral m edullary surface (VMS) elicited a reduction in respiratory frequency a nd phrenic inspiratory activity in halothane anesthetized rats. A dist inct cluster of neurons (nucleus parapyramidalis superficialis) was fo und in a superficial layer (10-150 mum from the surface)just beneath t he area where cooling produced suppression of respiration. The rat VMS layer contains neural substrates which regulate the respiratory rhyth m generation and inspiratory neural output.