A therapeutic dose of zolpidem reduces thalamic GABA in healthy volunteers: a proton MRS study at 4 T.
BACKGROUND
Zolpidem is a nonbenzodiazepine sedative/hypnotic that acts at GABA(A) receptors to influence inhibitory neurotransmission throughout the central nervous system. A great deal is known about the behavioral effects of this drug in humans and laboratory animals, but little is known about zolpidem's specific effects on neurochemistry in vivo.


OBJECTIVE
We evaluated how acute administration of zolpidem affected levels of GABA, glutamate, glutamine, and other brain metabolites.


METHODS
Proton magnetic resonance spectroscopy ((1)H MRS) at 4 T was employed to measure the effects of zolpidem on brain chemistry in 19 healthy volunteers. Participants underwent scanning following acute oral administration of a therapeutic dose of zolpidem (10 mg) in a within-subject, single-blind, placebo-controlled, single-visit study. In addition to neurochemical measurements from single voxels within the anterior cingulate (ACC) and thalamus, a series of questionnaires were administered periodically throughout the experimental session to assess subjective mood states.


RESULTS
Zolpidem reduced GABA levels in the thalamus, but not the ACC. There were no treatment effects with respect to other metabolite levels. Self-reported ratings of "dizzy," "nauseous," "confused," and "bad effects" were increased relative to placebo, as were ratings on the sedation/intoxication (PCAG) and psychotomimetic/dysphoria (LSD) scales of the Addiction Research Center Inventory. Moreover, there was a significant correlation between the decrease in GABA and "dizzy."


CONCLUSIONS
Zolpidem engendered primarily dysphoric-like effects and the correlation between reduced thalamic GABA and "dizzy" may be a function of zolpidem's interaction with alpha1GABA(A) receptors in the cerebellum, projecting through the vestibular system to the thalamus.
Licata
Stephanie C
SC
Behavioral Psychopharmacology Research Laboratory, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA. slicata@mclean.harvard.edu
Jensen
J Eric
JE
Penetar
David M
DM
Prescot
Andrew P
AP
Lukas
Scott E
SE
Renshaw
Perry F
PF
D000284:Administration, Oral; D000328:Adult; D001923:Brain Chemistry; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006179:Gyrus Cinguli / Q000378:metabolism; D006801:Humans; D006993:Hypnotics and Sedatives / Q000009:adverse effects / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011725:Pyridines / Q000009:adverse effects / Q000494:pharmacology*; D016037:Single-Blind Method; D011795:Surveys and Questionnaires; D013788:Thalamus / Q000378:metabolism*; D000077334:Zolpidem; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D006993:Hypnotics and Sedatives; D011725:Pyridines; D005973:Glutamine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000077334:Zolpidem