Effects of antihistaminic agents upon the electrographic activity of the cat brain: A power spectral density study

Abstract

The actions of three representative antihistaminics, tripelennamine (TPM), dipenhydramine (DPA), and ehlorpheniramine (CPA) on the electrical activity of the cat brain have been examined with the aid of power spectral density analysis. During the slow intravenous infusion of these drugs, DPA alone induced an increase in cortical synchrony but later induced cortical desynchrony like that seen throughout the infusions of TPM and CPA. Hippocampal theta (3.5–5 Hz) activity was induced by all 3 drugs, but computer analysis delineated subtle differences in the patterns of onset and dominance with the drugs, suggesting a greater complexity of hippocampal rhythms than previously reported. Bimodal activity in the range of 1–2 and 3–4.5 Hz was seen with all 3 drugs in reticular formation, thalamus and cortex, and in hippocampus as well with DPA and CPA. Total normalized cortical power approximated 100% throughout the infusion of TPM, while CPA and DPA cortical power values fluctuated and reached final values of approximately 200% just prior to paroxysm. All three drugs induced epileptiform paroxysms followed by hypersynchronous activity.