The major goal of this project is to study the membrane mechanisms involved in signalling thermal stimuli by nerve cells in the trigeminal ganglion which receives information from the face. A novel, miniature thermal stimulator is being developed which will apply highly localized and well-controlled heat stimuli to these trigeminal sensory neurons which are maintained in a cell-culture environment. This new instrument is based upon a commercially available miniature thermometer which utilizes a temperature-dependent change in the rate of decay of fluorescence emitted by a phosphor coating at the tip of a fiberoptic probe. The tip of the temperature probe functions as a black-body radiator by covering it with a layer of gold. A new optical assembly couples the optical fiber to both a xenon flash light and an infrared laser diode. Injection of both infrared and blue radiation into the optic fiber will make it possible to simultaneously heat the front of the probe and measure its surface temperature. By utilizing the temperature signal in a feedback loop and pulse-modulating the output of the infrared laser diode, it is possible to accurately control the highly localized heat stimuli. This new instrument should have many important applications in biological research.
