OBJECTIVETo evaluate the effects of theanine on sedative effects induced by pentobarbital sodium.

METHODThe locomotor activities of ICR mice induced by theanine (0.25, 0.5, 1.0, 2.0, 4.0 g x kg(-1)), pentobarbital sodium (5, 10 mg x kg(-1)) or the combination of both were determined with video-tracking system, and a novel index: Peripheral active time Peripheral time (PATP) was established. Hypnosis effect of combination of both was tested with right-reflex disappearance.

RESULTCompared with normal saline (74.52 +/- 20.4)%, theanine alone decreased this PATP in dose-dependent manner from (62.03 +/- 21.11)%, (56.44 +/- 21.69)%, (31.13 +/- 17.2)%, (25.06 +/- 10.03)% to (17.21 +/- 7.43)% (P>0.05, P<0.05, P<0.01, P<0.01 and P<0.01, respectively). Compared with pentobarbital sodium (5 mg x kg(-1)), between 0.25 g x kg(-1) and 1.0 g x kg(-1) theanine combined with that decreased peripheral PATP from (28.30 +/- 17.57)%, (30.64 +/- 17.21)% to (24.28 +/- 9.59)% (all P<0.01), and increased by 2.0 g x kg(-1) reversely (61.95 +/- 19.39)%. Compared with normal saline, pentobarbital sodium (10 mg x kg(-1)) and the combination with theanine decreased significantly PATP (all P<0.01). Compared with pentobarbital sodium (10 mg x kg(-1)), 0.25 g x kg(-1) theanine combined with that increased PATP [(25.37 +/- 13.68)% vs (10.08 +/- 7.98)%, P<0.01)] and 0.5 g x kg(-1), 1.0 g x kg(-1) theanine could depresse that increase [(14.56 +/-10.10)%, (8.24 +/- 4.08)% vs (10.08 +/- 7.98)%]. Total distance and peripheral active time showed the same or similar tendency in theanine alone or combination with pentobarbital sodium . Theanine enchanced hypnosis effect of pentobarbital sodium in dose-dependent manner.

CONCLUSIONTheanine can affect the sedative effect of low dose pentobarbital sodium in bidirectional action style but not change the hypnosis effect.