An apparatus was developed which permits the automated delivery of volatile chemical stimuli for use in neurophysiology experiments. A computer-controlled olfactometer, incorporating electronic mass flow controllers (EMFCs) and Teflon-lined solenoid valves, generated and delivered clean or odorized air. Neural and respiratory signals from the animal were amplified and stored, along with trial information (e.g. odorant concentration) on a chart recorder and video cassette recorder, both of which were controlled by the computer. This apparatus was used to measure responses to toluene from the rat ethmoid nerve, a part of the ophthalmic division of the trigeminal nerve. Multi-unit responses to this compound were first observed at 2000 p.p.m. The magnitude of the response increased linearly with logarithmic increases in concentration up to vapour saturation. Changes in respiration in response to toluene also were observed, although neural responses often were seen in the absence of respiratory changes.
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Silver et al. (1990) studied this question.