The 5-HT(1A) receptor active compounds (R)-8-OH-DPAT and (S)-UH-301 modulate auditory evoked EEG responses in rats

Schizophrenics commonly demonstrate abnormalities in central filtering capability following repetitive sensory stimuli. Such sensory inhibition deficits can be mirrored in rodents following administration of psycho-stimulatory drugs. In the present study, male Sprague-Dawley rats were implanted with brain surface electrodes to record auditory evoked EEG potentials in a paired-stimulus paradigm, using 87 dB clicks delivered 0.5 s apart. Amphetamine (1.83 mg/kg, i.p.) produced the expected loss of sensory inhibition, as defined by an increase in the ratio between test (T) and conditioning (C) amplitudes at N40, a mid-latency peak of the evoked potentials. Also, the 5-HT(1A) agonist (R)-8-OH-DPAT caused a significant increase in the TC ratio at the highest dose studied (0.5 mg/kg s.c.), while the 5-HT(1A) antagonist (S)-UH-301 did not significantly affect the TC ratio at any dose studied (0.1-5 mg/kg s.c.). When administered with amphetamine, a lower dose of 8-OH-DPAT (0.1 mg/kg) and the highest dose of UH-301 tested (5 mg/kg, s.c.) were able to reverse the amphetamine-induced increase in TC ratio. The findings suggest that 5-HT(1A) signaling is involved in sensory inhibition and support the evaluation of 5-HT(1A) receptor active compounds in conditions with central filtering deficits, such as schizophrenia.