Factors influencing the cholinesterases of cerebrospinal fluid in the anaesthetized cat.

Both acetylcholinesterase and non-specific cholinesterase are found in cerebrospinal fluid and blood plasma of the cat; the ratio of activities acetylcholinesterase/non-specific cholinesterase is about 1.5 in cerebrospinal fluid and 0.15 in plasma. A search was made for factors capable of influencing the concentration of the two cholinesterases in cerebrospinal fluid. Either the ventricular system was perfused with artificial cerebrospinal fluid from a lateral ventricle to the aqueduct, or the atlanto-occipital membrane was punctured and cerebrospinal fluid was collected continuously from the cisterna magna. Factors studied included: (a) procedures affecting the composition or formation of cerebrospinal fluid, such as changes in the ionic constituents of the perfusate, the inhibition of cerebrospinal fluid formation by acetazolamide or ouabain, or the rapid intra-carotid infusion of hypertonic urea; (b) arousal (noise or stimulation of the central ends of the sciatic nerves), or deepening of anaesthesia; (c) changes in blood pressure; (d) central stimulants and depressants, pyrogens, prostaglandins, antagonists of acetylcholine. Whereas most procedures or drugs tested increased the concentration of acetylcholinesterase, some central depressants (e.g. chlorpromazine) reduced, while another (ether) increased the appearance of acetylcholinesterase in the cerebrospinal fluid. The effect of ether was, in all probability, due to damage to the blood-brain barrier. A rise in acetylcholinesterase concentration was obtained upon stimulation of the central ends of the sciatic nerves; this was inhibited by atropine but not by N-methylatropine, indicating that the rise was due to increased nervous activity and not to the circulatory effects of the stimulation, since the changes in blood pressure caused by the stimulation remained the same after atropine administration. Amphetamine or leptazol raised the levels of acetylcholinesterase but it was not possible to determine whether this was due only to increased central nervous activity, since there was invariably leakage through the blood-brain barrier which by itself would be sufficient to produce the effect. A rise in the level of acetylcholinesterase was seen after administration of pyrogen; this was apparently not a simple effect of warming the body, but due to the action of the pyrogen on centers concerned with temperature control, since warming the animal by external heat failed to produce a similar change.(ABSTRACT TRUNCATED AT 400 WORDS)