Effects of noise on monoamine levels in the rat brain using in vivo microdialysis.

The concentrations of monoamines in the striatum, dorsal raphe and cortex of the brain of male Sprague-Dawley rats were monitored using in vivo microdialysis before, during and after noise exposure. Some 120 h after implantation of the microdialysis probe in the desired area, the rats were exposed to white noise (110 dB) for 20 min. The concentrations of monoamines in the dialysate were determined by HPLC. Exposure to white noise increased epinephrine in the striatum (42%) and dorsal raphe (39%), values then declined to baseline. In contrast, white noise decreased 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum (99%) and cortex (53%); these levels remained depressed following noise cessation. Noise also decreased homovanillic acid (HVA) in the striatum and in 5-hydroxy-indoleacetic acid (5-HIAA) in the striatum and dorsal raphe nucleus. Other neurotransmitters (norepinephrine etc.) did not change significantly in any region. These results suggest that noise influences monoamine levels differently in different brain regions.