Decreased Numbers of Somatostatin-Expressing Neurons in the Amygdala of Subjects With Bipolar Disorder or Schizophrenia: Relationship to Circadian Rhythms.
Growing evidence points to a key role for somatostatin (SST) in schizophrenia (SZ) and bipolar disorder (BD). In the amygdala, neurons expressing SST play an important role in the regulation of anxiety, which is often comorbid in these disorders. We tested the hypothesis that SST-immunoreactive (IR) neurons are decreased in the amygdala of subjects with SZ and BD. Evidence for circadian SST expression in the amygdala and disrupted circadian rhythms and rhythmic peaks of anxiety in BD suggest a disruption of rhythmic expression of SST in this disorder.



Amygdala sections from 12 SZ, 15 BD, and 15 control subjects were processed for immunocytochemistry for SST and neuropeptide Y, a neuropeptide partially coexpressed in SST-IR neurons. Total numbers (Nt) of IR neurons were measured. Time of death was used to test associations with circadian rhythms.



SST-IR neurons were decreased in the lateral amygdala nucleus in BD (Nt, p = .003) and SZ (Nt, p = .02). In normal control subjects, Ntof SST-IR neurons varied according to time of death. This pattern was altered in BD subjects, characterized by decreases of SST-IR neurons selectively in subjects with time of death corresponding to the day (6:00 am to 5:59 pm). Numbers of neuropeptide Y-IR neurons were not affected.



Decreased SST-IR neurons in the amygdala of patients with SZ and BD, interpreted here as decreased SST expression, may disrupt responses to fear and anxiety regulation in these individuals. In BD, our findings raise the possibility that morning peaks of anxiety depend on a disruption of circadian regulation of SST expression in the amygdala.
Translational Neuroscience Laboratory, Mclean Hospital, Belmont; Department of Psychiatry, Harvard Medical School, Boston, Massachusetts. Electronic address: hpantazo@mclean.harvard.edu.
Harry
H
Pantazopoulos
Translational Neuroscience Laboratory, Mclean Hospital, Belmont.
Jason T
JT
Wiseman
Translational Neuroscience Laboratory, Mclean Hospital, Belmont; Department of Psychiatry and Psychology, Mayo Clinic, Rochester, Minnesota.
Matej
M
Markota
Translational Neuroscience Laboratory, Mclean Hospital, Belmont.
Lucy
L
Ehrenfeld
Translational Neuroscience Laboratory, Mclean Hospital, Belmont; Department of Psychiatry, Harvard Medical School, Boston, Massachusetts; Program in Neuroscience, Harvard Medical School, Boston, Massachusetts.
Sabina
S
Berretta
D000679:Amygdala / Q000378:metabolism* / Q000503:physiopathology; D001714:Bipolar Disorder / Q000378:metabolism* / Q000503:physiopathology; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D009478:Neuropeptide Y / Q000378:metabolism; D012559:Schizophrenia / Q000378:metabolism* / Q000503:physiopathology; D013004:Somatostatin / Q000378:metabolism*
D009478:Neuropeptide Y; D013004:Somatostatin
Anxiety; Circadian; Gamma-aminobutyric acid; Interneuron; Mood disorder; Stress