Varied effects of atypical neuroleptics on P50 auditory gating in schizophrenia patients.
OBJECTIVE
Sensory gating deficits found in schizophrenia can be assessed by using a paired auditory stimulus paradigm to measure auditory evoked response. The ratio of the P50 response amplitude of the second or test stimulus to that of the first or conditioning stimulus is expressed as a percentage. Normal subjects generally suppress the second response and typically have ratios of less than 40%. Subjects with schizophrenia and half their first-degree relatives have deficits in sensory gating, with P50 ratios that are generally greater than 50%. Treatment with typical neuroleptics does not reverse this deficit. However, previous studies have shown that treatment with clozapine, an atypical neuroleptic, ameliorates this deficit in clinically responsive patients. This study sought to determine whether other atypical neuroleptics improve P50 ratios.


METHODS
P50 evoked potential recordings were obtained from 132 patients with schizophrenia and 177 healthy comparison subjects. Eighty-eight patients were being treated with atypical neuroleptics (clozapine [N=26], olanzapine [N=31], risperidone [N=22], and quetiapine [N=9]). Thirty-four patients were taking typical neuroleptics, and 10 were unmedicated.


RESULTS
Healthy subjects exhibited P50 suppression that was significantly better than the schizophrenia patients receiving typical neuroleptics (mean=19.8% [SD=21.0%] versus 110.1% [SD=87.9%]). Patients receiving atypical neuroleptics had a mean P50 ratio that fell between these two means (mean=70.4%, SD=53.7%). When patients treated with different atypical neuroleptics were compared, only the clozapine group had mean P50 ratios that were in the normal range. All other groups exhibited auditory P50 response inhibition that was significantly poorer than that of the healthy subjects.


CONCLUSIONS
Improvement in P50 gating appears to be greatest in patients treated with clozapine.
Box C268-26, Psychiatry, University of Colorado Health Science Ctr., 4200 East 9th Ave., Denver, CO 80262, USA.
Lawrence E
LE
Adler
Ann
A
Olincy
Ellen M
EM
Cawthra
Kara A
KA
McRae
Josette G
JG
Harris
Herbert T
HT
Nagamoto
Merilyne C
MC
Waldo
Mei-Hua
MH
Hall
Amanda
A
Bowles
Laurie
L
Woodward
Randal G
RG
Ross
Robert
R
Freedman
D000161:Acoustic Stimulation; D000328:Adult; D014150:Antipsychotic Agents / Q000494:pharmacology* / Q000627:therapeutic use*; D001307:Auditory Perception / Q000187:drug effects / Q000502:physiology; D001569:Benzodiazepines / Q000494:pharmacology / Q000627:therapeutic use; D003024:Clozapine / Q000494:pharmacology / Q000627:therapeutic use; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology; D003987:Dibenzothiazepines / Q000494:pharmacology / Q000627:therapeutic use; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D000077152:Olanzapine; D011569:Psychiatric Status Rating Scales; D000069348:Quetiapine Fumarate; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology*; D018967:Risperidone / Q000494:pharmacology / Q000627:therapeutic use; D012559:Schizophrenia / Q000175:diagnosis* / Q000188:drug therapy* / Q000235:genetics
D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D001569:Benzodiazepines; D000069348:Quetiapine Fumarate; D003024:Clozapine; D018967:Risperidone; D000077152:Olanzapine