Effects of perinatal vitamin B6 deficiency on dopaminergic neurochemistry

Long-Evans dams were fed either a vitamin B₆-deficient or a control diet from day 13-14 of gestation and throughout lactation. A control pair-fed group was also included because of differences in food intake between vitamin B₆-deficient and control ad libitum dams. The progeny of vitamin B₆-deficient dams had all the classic symptoms of B₆ deficiency. These included weight loss, ataxia, tremor, and epileptic seizures. Concentrations of the neurotransmitter dopamine (DA), and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), as well as D-2 dopamine receptor binding, 3,4-dihydroxyphenylalanine (DOPA) decarboxylase activity, and vitamin B₆ levels were measured in the corpus striatum of progeny at 7, 14, and 18 days after birth. Striatal DA and HVA levels were significantly decreased in B₆-deficient animals when compared to ad libitum or pair-fed controls. Daily injections of vitamin B₆ to deprived animals from the 14th to 18th day after birth improved the abnormal movement and normalized the concentration of DA but not of HVA in copus striatum. Striatal D-2 dopamine receptor binding using [³H]spiperone as ligand was significantly reduced in 18-day-old animals as compared to ad libitum and pair-fed controls. No significant differences were found at 14 days. The administration of vitamin B₆ to deprived animals did not raise the level of D-2 receptor binding during the period of observation. Scatchard plots indicated that the differences in binding were due to changes in reportor number and not in K(D). Corpus striatum DOPA decarboxylase activity with and without the addition of exogenous pyridoxal phosphate was significantly reduced in 14- and 18-day-old animals when compared to pair-fed controls. Vitamin B₆ levels in corpus striatum of deprived animals were significantly lower than control at all ages, substantiating the effect of the maternal deprivation. The results of these experiments suggest that perinatal vitamin B₆ deficiency produces significant alterations in the development of the dopaminergic system in the corpus striatum of the neonatal rat.