Fig. 5.

Pilocarpine levels from in vitro isolated guinea-pig brains. HPLC pilocarpine levels were measured in frozen isolated brains in which pilocarpine was perfused in vitro for 10 min at 800 μM in the presence (open circles) or in the absence (filled squares) of histamine, an agent known to increase the permeability of the BBB. The data points for pilocarpine levels are plotted against the time of washout of the drug. In these brains electrophysiological recordings were performed to verify the presence of seizure-like activity during histamine–pilocarpine co-application. The initial cerebral concentrations of the drug were obtained by extrapolating the time-dependent decay and by using y axis (mM) intercepts.