EFFECT ON BREATHING OF SURFACE VENTROLATERAL MEDULLARY COOLING IN AWAKE, ANESTHETIZED AND ASLEEP GOATS

In adult and neonatal goats, we chronically implanted thermodes on the ventrolateral (VLM) medullary surface to create reversible neuronal d ysfunction and thereby gain insight into the role of superficial VLM n eurons in control of breathing in anesthetized, awake and asleep state s. Consistent with data of others, cooling caudal area M and rostral a rea S caused sustained apnea under anesthesia. However, in the awake a nd NREM sleep states, cooling at this site caused only a modest reduct ion in breathing, indicating that neurons at this site are not critica l for respiratory rhythm in these states. Moreover, data in the awake state over multiple conditions suggest neurons at this site do not int egrate all intracranial and carotid chemoreception. The data suggest t hough that neurons at this site have a facilitatory-like effect on bre athing both unrelated and related to intracranial chemoreception. We b elieve that this facilitation serves a function similar to the facilit ation provided by the carotid chemoreceptors and by sources associated with wakefulness. Accordingly, elimination/attenuation of any one of these three influences (caudal M rostral S VLM, wakefulness, carotid c hemoreception) results in a slight decrease in breathing, removal of t wo of the three results in a greater decrease in breathing, and remova l of all three results in sustained apnea. (C) 1997 Elsevier Science B .V.