EFFECT OF VASOACTIVE DRUGS ON THE FLUID PRESSURE OF CAPSULES IMPLANTED INTO DOG BRAIN, SUBCUTANEOUS TISSUE AND MUSCLE

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Perforated capsules were implanted into the brain parenchyma, subcutaneous tissue, and muscle (denoted BC, SC, and MC, respectively) of dogs. After implantation, tissue grew and fluid was retained within the capsules. The effects of vasoactive drugs on the intracapsular fluid and cerebrospinal fluid (CSF) pressures were observed. Adrenalin and noradrenalin were used as pressor agents, and acetylcholine, isoproterenol, and isoxsuprine as depressor agents, together with certain other drugs. The following results were obtained:
1. The observed changes in CSF and intracapsular fluid pressures were largely dependent on the induced blood pressure changes following drug administration.
2. The CSF pressure was increased by both the pressor agents and depressor agents.
3. The SC and MC pressures were decreased by the pressor agents and generally increased by the depressor agents.
4. BC pressure was increased by the pressor agents and decreased mostly by isoproterenol, affected rather variably by isoxsuprine, while there was an initial decrease and subsequent increase with acetylcholine.
5. The pattern of these pressure responses in the BC fluid was clearly different from that in the CSF. The direction of pressure fluctuation in BC was opposite to that in both SC and MC.
6. Possible mechanisms for these capsular and CSF pressure fluctuations are discussed.