Background: Nicotine, the main ingredient in tobacco smoke, has always been linked to degenerative
changes to the nervous system and several areas in the brain were reported to be injured due to nicotine.
The effect of nicotine on the auditory system is only being recognized recently with few studies assessed the
morphology. The effect of nicotine on the primary auditory cortex of young adolescent animals was
addressed in this study. Materials & Methods: Twenty young male guinea pigs of two months old were
divided into two groups of 10 animals each. Group I, the control group, received daily subcutaneous
injections of normal saline for one month. Group II, the nicotine-treated group, received 3 mg/Kg body
weight of nicotine subcutaneously daily. After animal sacrifice, brains were removed and processed for light
and electron microscopic evaluations. Morphometry was also done to light microscopic histological sections.
Results: In the nicotine-treated group, there were degenerative changes affecting the neurons, glia as well
as blood capillaries. There was a darkening of neurons and disruption of their dendrites and organelles. The
glial cells revealed reactivity, swelling, and cytoplasmic disruption. Blood capillaries showed collapse and
thickening of their basement membrane. Morphometry revealed a decrease in the thickness of auditory
cortex as well as an increase in the number of dark neurons in the treated group versus the control.
Conclusion: Nicotine administration to adolescent male guinea pigs resulted in degenerative changes
affecting the auditory cortex of the brain, which emphasizes the hazardous effects of cigarette smoking,
especially at a young age.