Protocatechuic Acid Prevents Some of the Memory-Related Behavioural and Neurotransmitter Changes in a Pyrithiamine-Induced Thiamine Deficiency Model of Wernicke-Korsakoff Syndrome in Rats

Abstract

The purpose of this research was to investigate the effects of protocatechuic acid (PCA) at doses of 50 and 100 mg/kg on the development of unfavourable changes in cognitive processes in a pyrithiamine-induced thiamine deficiency (PTD) model of the Wernicke-Korsakoff syndrome (WKS) in rats. The effects of PCA were assessed at the behavioural and biochemical levels. Behavioural analysis was conducted using the Foot Fault test (FF), Bar test, Open Field test, Novel Object Recognition test (NOR), Hole-Board test and Morris Water Maze test (MWM). Biochemical analysis consisting of determination of concentration and turnover of neurotransmitters in selected structures of the rat CNS was carried out using high-performance liquid chromatography. PTD caused catalepsy (Bar test) and significantly impaired motor functions, leading to increased ladder crossing time and multiplied errors due to foot misplacement (FF). Rats with experimentally induced WKS showed impaired consolidation and recall of spatial reference memory in the MWM test, while episodic memory related to object recognition in the NOR was unimpaired. Compared to the control group, rats with WKS showed reduced serotonin levels in the prefrontal cortex and changes in dopamine and/or norepinephrine metabolites in the prefrontal cortex, medulla oblongata and spinal cord. PTD was also found to affect alanine, serine, glutamate, and threonine levels in certain areas of the rat brain. PCA alleviated PTD-induced cataleptic symptoms in rats, also improving their performance in the Foot Fault test. In the MWM, PCA at 50 and 100 mg/kg b.w. improved memory consolidation and the ability to retrieve acquired information in rats, thereby preventing unfavourable changes caused by PTD. PCA at both tested doses was also shown to have a beneficial effect on normalising PTD-disrupted alanine and glutamate concentrations in the medulla oblongata. These findings demonstrate that certain cognitive deficits in spatial memory and abnormalities in neurotransmitter levels persist in rats that have experienced an acute episode of PTD, despite restoration of thiamine supply and long-term recovery. PCA supplementation largely had a preventive effect on the development of these deficits, to some extent also normalising neurotransmitter concentrations in the brain.

Keywords: Wernicke–Korsakoff syndrome; behaviour; glutamate; memory; neurotransmitters; protocatechuic acid.

Figure 1

Experimental design, with timeline of treatments and behavioural testing.

Figure 2

The frequency of neurological symptoms recorded in animals during the period of pyrithiamine administration. The control group (no pyrithiamine and, hence, no PTD symptoms) is not visualised.

Figure 3

Changes in body weight (means ± SEM) in rats from the control group (Con), the PTD-induced WKS group (WKS), and the PTD-induced WKS groups treated with PCA at doses of 50 mg/kg (WKS + PCA50) or 100 mg/kg (WKS + PCA100) during the experiment. Between the administration of the first dose of pyrithiamine and the first dose of thiamine, there was a period of thiamine deficiency lasting 12 days (not applicable to control group).

Figure 4

Number of errors (mean ± SEM) per session in Foot Fault test, ** p < 0.01 vs. Con (ANOVA, post-hoc NK).

Figure 5

Time taken to cross the ladder (mean ± SEM) per session in Foot Fault test, * p < 0.05 vs. Con, ** p < 0.01 vs. Con, *** p < 0.005 vs. Con, **** p < 0.001 vs. Con, •• p < 0.01 vs. WKS.

Figure 6

Time (mean ± SEM) needed to correct the imposed body posture in the Bar test, * p < 0.05 vs. Con, **** p < 0.001 vs. Con, • p < 0.05 vs. WKS (ANOVA, post-hoc GH).

Figure 7

Learning progress in MWM acquisition phase as expressed by transfer latencies during successive trials of a 4-day training (mean ± SEM; four trials per day).

Figure 8

Transfer latency (mean ± SEM) in memory recall task in the MWM test, * p < 0.05 compared to Con, • p < 0.05 compared to WKS, •• p < 0.01 compared to WKS (ANOVA, post-hoc GH).

Figure 9

Number of crossings (mean ± SEM) over the previous platform location during the first memory test in MWM, post-hoc GH. * p < 0.05 compared to Con, • p < 0.05 compared to WKS, •• p < 0.01 compared to WKS.

Figure 10

Heat maps showing the spatial distribution of time spent by each group of animals at each pool location: (A) in the first memory test and (B) in the second memory test in MWM. The circle slices represent the SE and NW target quadrants along with platform location during the training phases (red circles in the lower right or upper left corner of each map).

Figure 11

Alanine concentration (mean ± SEM) in selected CNS structures in rats from the control group (Con), the PTD-induced WKS group (WKS), and the PTD-induced WKS groups administered PCA at doses of 50 mg/kg (WKS + PCA50) or 100 mg/kg (WKS + PCA100); * p < 0.05 vs. Con, ** p < 0.01 vs. Con, ••• p < 0.005 vs. WKS, •••• p < 0.001 vs. WKS, n/d—no data (concentration below detection threshold) (ANOVA, post-hoc NK).

Figure 12

Glutamate concentration (mean ± SEM) in selected CNS structures of rats from the control group (Con), the PTD-induced WKS group (WKS), and the PTD-induced WKS groups administered PCA at a dose of 50 mg/kg (WKS + PCA50) or 100 mg/kg (WKS + PCA100); ** p < 0.01 vs. Con, •• p < 0.01 vs. WKS, •••• p < 0.001 vs. WKS (ANOVA, post-hoc NK).