Bright artificial light produces subsensitivity to nicotine

Bright artificial light is a treatment for seasonal depression. Eleven (11) rats were exposed to bright artificial light (11,500 lux) for two consecutive weeks. The thermic response to nicotine was measured prior to light exposure and after one and two weeks of treatment. The thermic response to nicotine at baseline was -1.69 +/- 0.25 degrees C (mean +/- SEM). The thermic response to nicotine was -0.66 +/- 0.12 degrees C (p less than 0.002) after one and +0.31 +/- 0.14 degrees C (p less than 0.000025) after two weeks of light exposure. The change in temperature was different between weeks one and two (p less than 0.000025). The exposure of animals to constant light at an intensity of 300 lux did not blunt the hypothermic response to nicotine. These findings suggest that bright artificial light, like other antidepressant treatments, produces subsensitivity of a nicotinic mechanism involved in the regulation of core temperature.