Fast wave activity in the rat rhinencephalon: elicitation by the odors of phytochemicals, organic solvents, and a rodent predator.

Recent research has shown that bursts of approximately 20 Hz fast waves are elicited in rhinencephalic cortex in rats by the odors of a number of different organic solvents and of components of the secretions of predators such as the weasel and the fox. We now show that a number of phytochemicals (benzyl alcohol, carvacrol, eucalyptol, and salicylaldehyde) will elicit fast wave bursts of about 20 Hz in the rat pyriform cortex. Additional organic solvents (carbon tetrachloride, chloroform, diethyl ether, 1, 2-dimethoxyethane, n-heptane, mesitylene, methylcyclohexane, and commercial gasoline and kerosene, but not N,N-dimethylformamide or dimethyl sulfoxide) and another component of fox secretions (isopentenylmethyl sulfide) were also effective. Many of these compounds will also elicit fast wave bursts of about 20 Hz in the dentate gyrus. The effectiveness of benzyl alcohol, camphor, carvacrol, eucalyptol, isopentenylmethyl sulfide, 2-propylthietane, salicylaldehyde, toluene, and trimethylthiazoline (all of which elicit rhinencephalic fast waves in rats) in suppressing feeding in various small herbivores suggests that the recording of odor-induced rhinencephalic fast waves may provide an easy means of identifying new antifeedants. We found no evidence that the bursts of 20-Hz activity seen in the rat rhinencephalon were kindling-induced seizure-like reactions of the olfactory brain to the vapors of toxic chemicals.