gms | German Medical Science

Objective: Rats selectively bred for deficient prepulse inhibition (PPI), an operant measure of sensorimotor gating, may be used to study pathophysiological mechanisms and therapeutic strategies for neuropsychiatric disorders with abnormalities in information processing, such as schizophrenia and Tourette`s syndrome. The medial prefrontal cortex (mPFC) and the nucleus accumbens (NAC) have been shown to be involved in the regulation of PPI. Additionally, lesions of the entopeduncular nucleus (EPN) alleviated the PPI in rats with low PPI. We here examined the neuronal activity in the mPFC, NAC and EPN, since these areas are possibly involved in the pathomechanisms of prepulse inhibition (PPI) of the acoustic startle reaction.

Method: Male rats with breeding-induced high and low expression of PPI (n=6, each) were anesthetized with urethane (1.2 mg/kg). Extracellular single unit activity and local field potentials were recorded in the mPFC, NAC, and EPN for ten minutes, respectively.

Results: In PPI low rats, the discharge rate, measures of irregularity and the burst activity were significantly reduced as compared to the measures in PPI high rats (p<0.05), while analysis of the neuronal activity in the NAC and EPN showed no difference between groups. Additionally, the oscillatory theta band activity (4–8 Hz) was enhanced and the beta band activity (13–30 Hz) was reduced in all regions.

Conclusions: Reduced neuronal activity in the mPFC of PPI low rats may be one of the pathophysiological mechanisms leading to reduced sensorimotor gating. Interestingly, enhanced theta band activity has been found also in patients with Tourette’s syndrome and dystonia, i.e., disorders, which are accompanied by sensorimotor gating deficits.