Table 2: Preclinical studies on the effects of YKS on PD-like symptoms in animal models of neurological disorders.

SymptomsSpeciesInducerExtracts/componentsDose/route/regimenMajor findingHistological & biochemical evaluationReference

SleepMale ddY mice (4 weeks old and 20–25g)Social isolation for 9–12 weeksYKS300 mg/kg, p.o., 60 min prior to testingPentobarbital (50 mg/kg, i.p)-induced sleeping time ↑Sleep inducing effect involving the – benzodiazepine receptor complex, but not 5- receptors[22]
Male ddY mice (4–6 weeks old and 19–32 g)YKS300 mg/kg, p.o.Skin temperature ↓[23]

Depression and anxietyMale ICR mice 
(25–30 g)
Restraint stress for 14 daysYKS1000 mg/kg, p.o.Inhibition of decreased excitatory amino acid transporter 2 expression in the PFC and hippocampus[24]

AnxietyICR male mice (6 weeks old)Placed on elevated open-platformYKSCH800 mg/kg, p.o.Duration of freezing in EPM ↓Anxiolytic effects via a selective inhibitor of serotonin reuptake[25]
F344/N aged 
rats 
(24 months old)
AgingYKS3% (w/w) food pellets for 3 monthsTime and frequency 
in the open arm of the EPM ↑; the number of excrements during locomotor activity measurement ↓
Improved concentrations of serotonin and dopamine in the PFC using microdialysis and NH3 in plasma[26]
Male Wistar/ST rats (10-13 weeks old)Electric foot shock (aversive stressor)YKS1000 mg/kg, p.o., for 14 or 16 dayFreezing behavior ↓ in the CFC test; time spent in open arms ↑ in EPM test; unchanged locomotionAnxiolytic effects via 5- receptors in memory-dependent fear induced by aversive stress; plasma corticosterone (-) after CFC stress in rats that had experienced footshock stress[27]
Male ddY mice (4 weeks old)Social isolation stress for 6 weeksYKS1% and 3% (w/w) food pellets for 6 weeksRearing behavior ↓Anxiolytic effect mediated with 5- receptor[28]
Male Wistar rats (250–300 g)Cerebrovascular ischemia by the four-vessel occlusion methodYKS100, 300, or 1000 mg/kg, p.o., for 14 daysThe time in the dark box in the light/dark test and in the enclosed arm in EPM ↓; the proportion of counts in the outer area in OF test ↓; unchanged locomotion in the open-fieldAntagonistic effect on wet-dog shakes induced by 5-agonist, DOI (5 mg/kg)[29]
Male ICR miceCFC 
consisting of inescapable foot-shocks
Co-treatment SSRI (fluvoxamine) +YKSFluvoxamine (5–20 mg/kg, i.p.) and YKS (0.3 and 1 g/kg, p.o.) for 6 daysFreezing behavior characterized as anxiety behavior ↓ in CFCDecreased 5-, but not 5- receptor expression in the PFC[30]
F344/N male rats (10-13 weeks old)Restraint stress for 1 hYKS100 or 300 mg/kg, p.o., for 1 h (single) or for 2 weeks (repeated)Anxiety-related behavior in repeated administration ↓; unchanged locomotion by OF and EPM testDecreased stress-induced c-Fos expression in the medial PFC and the basolateral and medial amygdaloid nuclei; serum corticosterone levels (-)[31]

HallucinationMale ddY mice (4 weeks old)Isolation stress for 6 weeks; DOI, 2.5 mg/kg (i.p.)YKS1% and 3% (w/w) food pellets for 6 weeks or oralDOI-induced head-twitch response ↓Down regulation of 5- receptor density in the PFC[32]
Male ddY mice ( 4 weeks old and 20–25 g)DOI, 5 mg/kg, i.p.YKS300 mg/kg, p.o., for 14 days repeated treatmentDOI-induced head twitch response ↓Decreased expression of 5- receptors in the prefrontal cortex[33]

AggressivenessMale Wistar rats (7 weeks old)Social isolation for 11-13 
weeks
YKS100, 300 mg/kg, p.o.Aggressive behavior ↓ using aggression test[34]
Male ddY mice (5 weeks old)MethamphetamineMethamphetamine-induced 
hyperlocomotion ↓
Inhibition of hyperlocomotion via dopaminergic signaling
Male ddY mice (6 weeks old)Injection of Aβ into the lateral ventricle of the brainYKS0.5 or 1.0 g/kg for 3 weeksAggressive 
behaviors including tail rattling, chase, and attack ↓
[35]
Male Wistar rats (6 weeks old)Injection of L-Glutamic acid into the right NBMYKSCH1.0 g/10 ml/g for 7 daysAggressive behavior in resident-intruder tests ↓Mediated by 5- receptor stimulation[36]
Male Wistar rats (7 weeks old)Injection of PCAYKS0.5 or 1.0 g/kg single or chronic (2 weeks) after PCA injectionAggressive behavior ↓Agonistic effect on 5- receptors as buspirone (5- agonist) and chronic treatment with YKS inhibited aggressive behavior in PCA-injected rats[37]
Male ddY mice (3 weeks old)Isolated zinc-deficient diet for 2 weeksYKSDrinking water containing YKS 300 mg/kgAggressive behavior in resident-intruder test ↓ Suppression of glutamatergic neuron activity; MK-801 (NMDA receptor antagonist) attenuated aggressive behavior in zinc-deficient mice[38]
Male ddY mice (3 weeks old)Zinc-deficient diet for 2 weeksYKSDrinking water containing YKS 300 mg/kgAggressive behavior in resident-intruder test ↓Lower serum glucocorticoid levels and ameliorated increased glutamate and GABA concentrations in brains of zinc-deficient mice[39]
Male ddY mice (3 weeks old) and male Wistar rats (3 
weeks old)
Zinc-deficient diet for 2 weeksYKSCHDrinking water containing YKSCH 300 mg/kg 
for 2 weeks
Aggressive behavior in resident-intruder test ↓Attenuation of excess exocytosis at mossy fiber boutons induced with 60 mM KCl in hippocampus and intracellular Ca2+ level by GA (100–500 μM) or GM (100 μM)[40]

CognitionTg2576 mouse (5-15 months old)ADYKSPowdered diets containing 0.5 and 1.0% YKS for 10 monthsLearning disturbance in the Morris water-maze test ↓; time spent in the open arms in EPM test ↑; hyperactivity in OF test ↓No inhibition of histological deposition or amounts of Aβ observed in Tg(+) mice[41]
Male Wistar rats (300–350 g)Repeated cerebral ischemiaYKS and Angelica root1000 mg/kg, p.o. for 7 daysCorrect choice in 8 RAM task ↑Upregulated the release of ACh; prevented 4-VO-induced hippocampal apoptosis[42]
Male Wistar 
rats (230–270 g)
Four-vessel transient cerebral ischemia and Injection of Aβ into intracerebroventricularlyYKS100, 300, or 1000 mg/kg, p.o. for 2 weeksCorrect choices ↑ and error choices ↓ in the 8 RAM taskIncrease of high K+-evoked potentiation of ACh release and expression of dynamin 1 in the hippocampus and leading to improved synaptic function[43]
OBX male ddY mice (9 weeks old)ADYKS375–750 mg/kg, p.o.Memory deficits in modified Y-maze test and novel object recognition test ↓; long term memory impairment in fear conditioning test (-)Reversed OBX-induced down-regulation of ChAT and muscarinic M1 receptor expression without affecting muscarinic M3 receptor expression or AChE activity[44]
Naive male F344/N rats (24 months old)AgingYKS3% (w/w) food pellets for 3 monthsAccuracy in the delayed alternation ↑ (working memory); accuracy in reversal discrimination tasks ↑ 
(reversal learning)
Increase of dopaminergic signaling through D1 receptors in the PFC as the effect of YKS was reduced by intracranial infusion of a dopamine D1 receptor antagonist[45]
Male Wistar rats (3 weeks old and 35-45g)Thiamine-deficient dietYKSDrinking water containing YKS 0.5, 1.0 g/kgMemory disturbance 
in step-through passive-avoidance test ↓
Inhibition of neuronal and astroglial cell degeneration in the brainstem, hippocampus, and cortex; inhibition of extracellular glutamate rise in the ventral posterior medial thalamus[46]
Male homozygous (j/j) Gunn rats 
(7 weeks old)
Gunn rat, animal model of schizophreniaYKSDrinking water containing YKS 1 g/kgLocation index in object-location test ↑Suppression of microglial activation 
and promotion of neurogenesis in the hippocampus
[47]

MotorMale Mongolian gerbils (60–80 g)Cerebral ischemia by occlusion of bilateral common carotid arteries for 5 minYKS300 mg/kg, p. o. for 30 daysIschemia-induced locomotor hyperactivity ↓; errors recorded in the 8-RAM task ↓Decreased number of activated microglia in the CA1 based on Iba1 immunohistochemistry; amelioration of ischemia-induced oxidative DNA damage via 8-OHdG assay[48]

PainMale SD rats (250-300g)Chronic constriction injuryYKS0.3, 1.0 g/kg, p.o.Mechanical allodynia in the von Frey filament test ↓; cold allodynia in acetone test ↓Inhibition of cerebrospinal fluid dialysate levels of glutamate; DL-threo-beta-hydroxyaspartate and dihydrokainate as glutamate transporter inhibitor reduced the antiallodynic effects of YKS[49]
Male ICR mice (5 weeks old)Partial sciatic nerve ligationYKS1 g/kg, p.o.Mechanical allodynia in the von Frey filaments test ↓Inhibition of IL-6 mRNA expression in astrocytes and/or microglia in the spinal cord[50]

Tardive dyskinesiaMale Wistar rats (5 
weeks old)
Injection of haloperidol decanoate-into thigh muscleYKS0.1, 0.5 g/kg, p. o. for 3 weeksVacuous chewing movement ↓Inhibition of increased striatal glutamate and GLT-1 mRNA levels in haloperidol-treated rats[51]

DOI=1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, CFC=contextual fear conditioning, EPM=elevated plus-maze, OF=open-field, PFC=prefrontal cortex, Ach=acetylcholine, RI=repeated ischemia, ChAT=choline acetyltransferase, AchE=acetylcholinesterase, RAM=radial arm maze, YKSCH=Yokukansankachimpihange, PCA=para-chloroamphetamine, AD=Alzheimer’s disease, Aβ=amyloid β, GA=18β-glycyrrhetinic acid, GM=geissoschizine methyl ether, and 4-Vo=4-vessel occlusion.