C-Fos protein expression in the mouse brain: effects of nicotine aerosol.

Tobacco products are predominantly consumed through inhalation of nicotine-containing aerosols, with nicotine producing significant sensory stimulation effects. Existing research indicates that organic acid components can modulate the neurostimulatory properties of tobacco products. This study aimed to investigate the combined effects of nicotine and citric acid aerosols on neural activity in the male mouse brain. By establishing a group aerosol exposure protocol and utilizing c-Fos protein as a neuronal activity marker, we demonstrated that nicotine aerosol exposure significantly enhanced c-Fos expression in several brain regions including the hypothalamus, amygdala, midbrain, and olfactory-related areas. Notably, citric acid effectively attenuated the nicotine-induced enhancement of neuronal activity, with significantly reduced c-Fos expression observed in specific brain regions including the amygdalopiriform transition area (APir), basolateral amygdaloid nucleus (BLA), anterior medial amygdalar (MeA), lateral preoptic nucleus (LPO), medial habenular nucleus (MHb), and accumbens nucleus (NAc) compared to the nicotine group. This study reveals the regulatory role of organic acids on the neurostimulatory effects of nicotine, providing a theoretical basis for modulating the sensory characteristics of tobacco products.