Highly Sensitive Neurons
Inhaled agents can alter excitability in many different anatomic
regions of the brain or spinal cord. However, within each discrete area of the CNS,
there may exist a relatively small number of neurons that are exquisitely sensitive
to anesthetics. The existence of such highly sensitive cells is demonstrated in
molluscan ganglia having endogenous firing activity.[34]
[35]
The firing activity may be
completely inhibited in selected neurons at halothane concentrations of about 1 MAC
( Fig. 4-6
),[34]
[35]
with other neighboring neurons exhibiting little
alteration in neuronal firing activity. There may even exist supersensitive sites
in the CNS (i.e., sites that are maximally inhibited at anesthetic concentrations
substantially less than MAC) that are related to the anesthetic-induced production
of amnesia.[36]
