AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 2 295-R302, Copyright © 1986 by American Physiological Society
Effect of focal cooling of central chemosensitive areas on cerebral ischemic response
N. R. Prabhakar, J. Mitra, W. Van de Graaff, M. A. Haxhiu and N. S. Cherniack
The ventrolateral medullary surface (VMS) has been shown to have
chemosensitive areas that can alter blood pressure and respiration. It has
also been shown that lesions near the VMS can affect the intensity of the
cerebral ischemic response (CIR). To determine which regions of the central
chemosensitive areas of the ventral medullary surface contribute to the
pressor response caused by cerebral ischemia, we used focal cooling of the
caudal Loescheke's (CL), intermediate Schlaefke's (IS), and rostral
Mitchell's (RM) areas of VMS during ischemia of the brain. Experiments were
performed on 17 pentobarbital sodium-anesthetized, paralyzed, and
artificially ventilated cats after denervation of the vagi and sinoaortic
nerves. Bilateral occlusion of the external carotid and vertebral arteries
resulted in a significant increase of arterial pressure (from 129 +/- 4 to
174 +/- 8 mmHg, P less than 0.01) and an increase in splanchnic sympathetic
activity. However, heart rate and cervical sympathetic activities were not
appreciably affected by cerebral ischemia. Bilateral cooling of the IS area
to as low as 10 degrees C led to a decrease or disappearance of phrenic
activity but failed to affect the magnitude of the pressor response. Also
cooling of the CL and RM areas and application of Gelfoam pledgets soaked
in lidocaine (4%) to these areas did not affect the CIR. However, covering
the whole VMS with 0.2 ml of 4% lidocaine or cold cerebrospinal fluid (10
degrees C) abolished the ischemic reflex.(ABSTRACT TRUNCATED AT 250 WORDS)
