TTX Blocks Baclofen-induced Phase Shifts of the Mammalian Circadian Pacemaker in Vitro
The mammalian circadian pacemaker, located in the suprachiasmatic nucleus (SCN), expresses 24-h rhythms when isolated in vitro. The GABAA agonist, muscimol, induces phase advances during the mid-subjective day, while the GABAB agonist, baclofen, induces both daytime phase advances and nighttime phase delays. Here, we present evidence that tetrodotoxin (TTX) completely blocks baclofen-induced phase shifts in vitro, but does not block in vitro phase advances induced by muscimol. These results suggest that GABAA, but not GABAB, receptors are located on SCN pacemaker cells.
Harriet E. Bergeron, Blaine Danielson, Kevin R. Biggs, Rebecca A. Prosser, TTX blocks baclofen-induced phase shifts of the mammalian circadian pacemaker in vitro, Brain Research, Volume 841, Issues 1-2, 11 September 1999, Pages 193-196, ISSN 0006-8993, DOI: 10.1016/S0006-8993(99)01791-6. (http://www.sciencedirect.com/science/article/B6SYR-3XMGP1C-1N/2/e38cabf25c7bc2f309425678bcb83f89)