mersalyl and amyl-acetate

1. A rat olfactory preparation, suitable for biochemical studies in vitro on olfactory mechanisms, is described. 2. The effects of the impermeant chemical modification reagents mersalyl (a thiol reagent) and enzymatic iodination, on the amplitude of the electroolfactogram (EOG) responses elicited from rat olfactory mucosa by pulses of odorant vapours was studied using 12 odorants differing widely in odour quality and molecular structure: amyl acetate, carvone, decanal, butylamine, cineole, citronellol, cresol, diacetyl, dimethylethyl-pyrazine, naphthalene, octanethiol and valeric acid. 3. Both reagents irreversibly reduced the EOG amplitude to all odorants to an extent dependent on the reagent concentration. Two subpopulations of animal preparations could be distinguished on the basis of the extent to which they survived the iodination whereas mersalyl appeared to sample a single population of preparations. 4. Small but statistically significant differences were observed between the responses of each odorant with each reagent but no simple correlation between either the molecular structure or odour quality of the odorants and the reagent effect is apparent for the case of mersalyl. With iodination the responses from the three flexible-aliphatic-chain odorants were reduced to a greater extent than the other odorants, all of which had a dissimilar molecular structure. 5. The ability of three odorants, amyl acetate, carvone and decanal, to protect the receptors for the odorants against chemical modification was investigated. The protecting odorants were applied directly to the mucosa as a dilute solution in Ringer's medium. No specific odorant protection effects were observed. 6. The results are discussed in relation to a model of the olfactory mechanism involving relatively non-specific receptor proteins. Each receptor type is envisaged as interacting weakly with a number of odorants and each odorant interacts with a number of receptors.

Topics: Aldehydes; Animals; Cyclohexane Monoterpenes; Electrophysiology; In Vitro Techniques; Iodine; Male; Mersalyl; Monoterpenes; Odorants; Olfactory Mucosa; Pentanols; Rats; Rats, Inbred Strains; Sensory Receptor Cells; Sulfhydryl Reagents; Terpenes

The effects of thiol-specific reagents on the amplitude of the electro-olfactogram (E.O.G.) responses elicited from frog olfactory mucosa by pulses of odorant vapours was studied. The impermeant thiol-specific reagent mersalyl [(3-{[2-(carboxymethoxy)-benzoyl]amino}-2-methoxypropyl)hydroxymercury monosodium salt] brings about a rapid decrease in the E.O.G. signal obtained with the odorant pentyl acetate. The extent of the decrease is proportional to the concentration of the mersalyl applied and the effect of the reagent is partially but incompletely reversed by treatment of the labelled mucosa with dithiothreitol. The sites labelled by mersalyl can be protected by pretreating the mucosa with a dilute solution of the odorant pentyl acetate and leaving the solution in contact with the tissue after the addition of mersalyl. When the protecting odorant is washed out of the tissue, the original E.O.G. amplitude is regained. Pentyl acetate applied to the mucosa protected the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: n-butyric acid, n-butyl acetate, phenylacetaldehyde and cineole (1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane). The pentyl acetate applied to the mucosa failed to protect the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: butan-1-ol, benzyl acetate, nitrobenzene, beta-ionone and linalyl acetate. The significance of the differential protection effects for the odour-quality-coding mechanism in the olfactory primary neurons is discussed. It is suggested that the olfactory code at this level of the olfactory system may be elucidated by chemical-modification methods.

Topics: Acetates; Animals; Anura; Binding Sites; Electrophysiology; Mersalyl; Olfactory Mucosa; Organomercury Compounds; Pentanols; Rana temporaria