Cataleptic effects of gamma-hydroxybutyrate (GHB), its precursor gamma-butyrolactone (GBL), and GABAB receptor agonists in mice: differential antagonism by the GABAB receptor antagonist CGP35348.
BACKGROUND
Gamma-hydroxybutyrate (GHB) is used to treat narcolepsy but is also abused. GHB has many actions in common with the GABA(B) receptor agonist baclofen.


OBJECTIVE
To further study the role of GABA(B) receptors in the effects of GHB.


METHODS
The experiments examined the ability of the GABA(B) receptor antagonist CGP35348 to attenuate GHB-induced catalepsy in comparison with its ability to attenuate the cataleptic effects of GABA(B) receptor agonists.


RESULTS
In C57BL/6J mice, GHB, the GHB precursor gamma-butyrolactone (GBL), and the GABA(B) receptor agonists baclofen and SKF97541 all produced catalepsy but differed in potency (i.e., SKF97541>baclofen>GBL>GHB) and in onset of action. The cataleptic effects of drug combinations were assessed at the time of peak effect of each compound, i.e., 60 min after CGP35348 and 60, 30, 30, and 15 min after baclofen, SKF97541, GHB, and GBL, respectively. At 100 mg/kg, CGP35348 shifted the dose-response curves of baclofen and SKF97541 to the right but not those of GHB and GBL; at 320 mg/kg, CGP35348 shifted the curves of all four compounds to the right.


CONCLUSIONS
The finding that CGP35348 was about threefold less potent to antagonize GHB and GBL than baclofen and SKF97541 is further evidence that the mechanisms mediating the effects of GHB and GABA(B) agonists are not identical. Differential involvement of GABA(B) receptor subtypes, or differential interactions with GABA(B) receptors, may possibly explain why GHB is effective for treating narcolepsy and is abused whereas baclofen is not.
Koek
Wouter
W
Department of Psychiatry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. koek@uthscsa.edu
Mercer
Susan L
SL
Coop
Andrew
A
D015107:4-Butyrolactone / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001418:Baclofen / Q000008:administration & dosage / Q000494:pharmacology*; D002375:Catalepsy / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D018755:GABA Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D018756:GABA Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D058786:GABA-B Receptor Agonists; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009290:Narcolepsy / Q000188:drug therapy; D009943:Organophosphorus Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D018080:Receptors, GABA-B / Q000187:drug effects; D012978:Sodium Oxybate / Q000008:administration & dosage / Q000494:pharmacology*; D019966:Substance-Related Disorders
D018755:GABA Agonists; D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D009943:Organophosphorus Compounds; D018080:Receptors, GABA-B; C068457:3-aminopropyl(methyl)phosphinic acid; D012978:Sodium Oxybate; C066430:CGP 35348; D001418:Baclofen; D015107:4-Butyrolactone