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Previous human studies revealed that l -theanine influences brain function. The current study was designed to evaluate the affect of l -theanine (Suntheanine®) on attention and reaction time response in 18 normal healthy University student volunteers. In accordance with preliminary analysis of the manifest anxiety scale (MAS), the subjects were divided into two groups referred to as high anxiety propensity group and the minimal anxiety propensity group. Both groups received l -theanine (200 mg/100 ml water) and placebo (100 ml water) in a double blind repeated measurement design protocol. Assessments were performed for 15–60 min after consumption under a relaxed condition upon exerting an experimentally induced visual attentional task as well as audio response tests. Self-reports of anxiety as State-Trait Anxiety Inventory (STAI) was characterized at post experiments. Alpha bands electroencephalographic activity and heart rate were recorded throughout the trial. The results demonstrate the significant enhanced activity of alpha bands, descending heart rate, elevated visual attentional performance, and improved reaction time response among high anxiety propensity subjects compared to a placebo. However, no significant differences were noticed among subjects with a minimal anxiety propensity. Results evidently demonstrated that l -theanine clearly has a pronounced effect on attention performance and reaction time response in normal healthy subjects prone to have high anxiety.

The role of glutamate receptors in the inferior colliculus (IC) in audiogenic and audiogenic-like seizures was investigated in adult rats with transient neonatal hypothyroidism by 0.02% propylthiouracil (PTU) treatment through mother's milk (PTU rats) and in naive rats treated intracisternally with N-methyl- d -aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA), or cyclothiazide, an inhibitor of rapid AMPA receptor desensitization. All rats showed audiogenic or audiogenic-like seizures characterized by running fit (RF) and generalized tonic–clonic seizures (GTCS). While systemically administered MK-801 inhibited GTCS, intracisternally administered NBQX inhibited RF and GTCS in both audiogenic and audiogenic-like seizures. Auditory stimulation shortened the latency to GTCS induced by AMPA, but not NMDA, at a subclinical dose and further elongated the shortened duration of RF, but not GTCS, induced by MK-801 pretreatment. Furthermore, Northern blot analysis was used to evaluate the expression of the immediate-early gene c-fos in the IC following induction of audiogenic or audiogenic-like seizures. The significant induction of c-fos mRNA by audiogenic seizures in PTU rats or by AMPA- or cyclothiazide-induced seizures in naive rats was prominent in the IC. MK-801 suppressed c-fos mRNA expression in the IC induced by audiogenic seizures in PTU rats or by AMPA-induced seizures in naive rats. NBQX suppressed the expression of c-fos mRNA in the IC induced by AMPA-induced seizures but did not suppress c-fos mRNA in PTU rats or rats with cyclothiazide-induced seizures. Auditory stimuli failed to affect c-fos mRNA induction by AMPA. The present study suggests that audiogenic-like seizures can be reproduced by glutamate receptor agonists in which AMPA receptors are primarily linked to the initiation of audiogenic seizures (RF) while NMDA receptors presumably located within the IC are involved in the propagation of GTCS in audiogenic seizures.

Purpose: This study was conducted to assess the effect of NMDA receptor antagonists (MK-80 I and CPP) and a non-NMDA receptor antagonist (NBQX), administered into inferior colliculus (IC) or into the ambient cistern on audiogenic seizures i n rats neonatally exposed to propylthiourecil (PTU). Furthermore, the role of glutamatc rcceptor subtypes i n audiogenic seizures was cxanincd by analysis of behavioral manifcstations induced hy inttacisternal injection of NMDA or AMPA in naive rats. Methods: I. Rats were exposed to 0.02% PTU through the mother's milk from day 0 to day 19 (PTU rats). Those animals were tested for audiogcnic scizure susceptibility at the age of 10 wccks. PTU rats without generalized tonic-clonic scizurc (GTCS) after auditory stimulation wcrc excluded i n this study. MK-801 at doscs of 2, 20, 40 nmol/side (n = 2, I I, 5), CPP at doscs of 0.04, 0.4, 4 nmol/side (11 = I I, 5, 13), or NBQX at doscs of 2, 20 imnol/side (n = 3, 13) was bilatcrally;idministered into IC. Thiriy minutcs aftcr treatment of drugs, auditory stimulation wiis applied by ringing the emergency bell (1 12 dB) [or 80 scc. The latency to running fit (RF) and GTCS, and the duration 0 1 RF and GTCS wcrc observed i n each tested animal. MKX O I at doses of 0.02, 2, 40 nmol/brain (n = 6, 5, 5), CPP at doses of 0.04, 0.4, 4 nmol/hrain (n = 6, 6, h), or NBQX at doses of 0.5, 5 nmol/brain (n = 6, 6) was administered inio cisterna ambicncc of PTU rats. Five minutes after treatment of drugs, the audiogenic seizures wcrc obscrved as stated above. 2. Naive Spraguc-Dawlcy rats were used at 7 weeks of age. NMDA at doscs of 10, 20 pglbrain (n = 10, 5) or AMPA at doses of 3, 6 pg/brain (11 = 6, 7) was administcrcd into cisterna ambience. After trcatincnt of NMDA or AMPA, the behavioral changes wcrc observed for 30 minutes. Furthermore, aftcr trcatment of NMDA 5 pg/hrain (n = 4) or AMPA 3 @brain (n=6), the behavioral changes were obscrvcd i n cach tested animal during 80 seconds with auditory stimulation. AMPA 3 pg/brain was administered into cisterna arnbiencc after pre-trciitmcnt of systemic administration or MK-801 0.5 mg/kg. The behavioral changes of the prc-treated animals were comparcd with those of non pre-treated animals during 80 scconds with auditory stimulation. Results: I. In PTU rats the microinjection of CPP into 1C at 0.4, 4 nmol/side was found to exhibit significant blocking effects on both RF and GTCS. NBQX at 20 nmollside inhibited only GTCS. 2. intracisternal injection of MK-801, CPP, or NBQX showed significant block-ing effects on both RF and GTCS in PTU rats. 3. Thc intracistcrnal administration of NMDA or AMPA in naive rats dose-dependently elicitcd RF lollowcd by GTCS similar to audiogenic seizurcs in PTU rats. 4. Auditory stimulation augmented both RF and GTCS induced by subclinical dose of AMPA in naive rats but failed to affect the procon vulsant action of NMDA. This augmentative effect was inhibited by MK-80 I. Conclusion: These results suggest that both NMDA and AMPA receptor activation arc ncccssary to induce RF. In audiogcnic scizurcs, thc auditory stimulation probably is equivalent to the activation of NMDA receptors, and thc relay mcchanism from RF to GTCS is presumably related to NMDA receptors.