Ginkgo-specific acylated flavonol glycosides modulate neurotransmitter and improve motor coordination in rats

We previously observed that sub-chronic treatment (14 days) with two Ginkgo-specific acylated flavonols (3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)-quercetin [Q] and 3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)-kaempferol [K]) increases dopamine and acetylcholine levels in the rat medial prefrontal cortex (PFC) and it was speculated that these two flavonoids contribute to the dopamine enhancing properties of the special Ginkgo biloba extract EGb 761^® [1]. Depending on the brain region, the pharmacological effects of dopamine release are different. Beside emotional and cognitive functions in the PFC, dopamine is the main neurotransmitter in the nigrostriatal pathway and plays a significant role in the control of motor function. Thus, it was hypothesized that these two flavonoids may also improve motoric dysfunction by modulation of dopaminergic neurotransmission. We therefore, evaluated the influence of these flavonoids on motor coordination in the rotarod test using spontaneously-hypertensive rats (SHR). This rat strain displays insufficiencies in fine motor skills and is used as a rodent model of attention deficit hyperactivity disorder (ADHD). Following oral administration, both flavonoids dose-dependently increased the time animals stayed on the rotating rod before falling off (see table).

Dose (mg/kg, p.o.)	Q Time on rotarod (s)	K Time on rotarod (s)
0	62 ± 90	124 ± 120
3	112 ± 111	110 ± 108
10	163 ± 94 *	202 ± 95
30	224 ± 84 #	290 ± 22 #
* p < 0.05 vs. vehicle group; # p < 0.01 vs. vehicle group

The results suggest that these flavonoids as well as EGb 761^® may be useful in the therapy of coordination disorders such as ADHD, Parkinson's disease or presbyvertigo.

References:

[1] Kehr et al. Int Psychogeriatr. 2012; 24 Suppl 1: S25