Changes in open-field activity and novelty-seeking behavior in periadolescent rats neonatally treated with monosodium glutamate

Abstract

Monosodium glutamate (MSG) treatment of neonatal rodents leads to degeneration of the neurons in the arcuate nucleus, inner retinal layers and various other brain areas. It also causes various changes in the motor activity, sensory performance and learning abilities. We have previously shown that MSG treatment delays the appearance of some reflexes during neurobehavioral development and leads to temporary changes in reflex performance and motor coordination. Investigation of novelty-seeking behavior is of growing importance for its relationship with sensitivity to psychomotor stimulants. Perinatal administration of numerous toxic agents has been shown to influence novelty-seeking behavior in rats, but little is known about the influence of neonatal MSG treatment on the novelty-seeking behavior. The aim of the present study was to compare changes in locomotor, spontaneous exploratory and novelty-seeking behavior in periadolescent rats neonatally treated with MSG. Newborn rats were treated with 4 mg/g MSG subcutaneously on postnatal days 1, 3, 5, 7 and 9. Open-field behavior was tested at 2, 3, 4, 6 and 8 weeks of age. We found that MSG administration led to only temporary increases in locomotor behavior, which was more pronounced during the first few postnatal weeks, followed by a subtle hypoactivity at 2 months of age. Novelty-seeking was tested in four 5-min trials at 3 weeks of age. Trial 1 was in an empty open-field, two identical objects were placed in the arena during trial 2 and 3, and one of them was replaced to a novel object during trial 4. We found that the behavioral pattern of MSG-treated rats was the opposite in all tested signs in the novelty exploration test compared to control pups. In summary, our present study shows that neonatal MSG treatment leads to early temporary changes in the locomotor activity followed by hypoactivity at 2 months of age. Furthermore, MSG-treated rats show a markedly disturbed novelty-seeking behavior represented by altered activity when subjected to a novel object.

Neuronal Damage Induced by Perinatal Asphyxia Is Attenuated by Postinjury Glutaredoxin‐2 Administration

“…This excitotoxicity has shown to be most severe in the retina, in the cortex, and in the hippocampus [82, 85–88]. Moreover, glutamate excitotoxicity has also been previously linked to neurobehavioral delays [82, 85]. Interestingly, the biochemical findings of this study showed that both Grx2 and Trx1 acted in the biomarker reduction associated with the glutamate excitotoxicity pathway which was increased after hypoxia/ischemia (Figure 2).…”

“…During this period, different insults, such as a hypoxic/ischemic event, can affect the normal development of those reflexes and physical skills [30, 82–84]. Previous studies have shown that glutamate neurotoxicity plays a key role in the impairment of the development of neurological reflexes and motor skills [82, 85]. This excitotoxicity has shown to be most severe in the retina, in the cortex, and in the hippocampus [82, 85–88].…”

“…Previous studies have shown that glutamate neurotoxicity plays a key role in the impairment of the development of neurological reflexes and motor skills [82, 85]. This excitotoxicity has shown to be most severe in the retina, in the cortex, and in the hippocampus [82, 85–88]. Moreover, glutamate excitotoxicity has also been previously linked to neurobehavioral delays [82, 85].…”

Asiatic acid, a pentacyclic triterpene in Centella asiatica, attenuates glutamate-induced cognitive deficits in mice and apoptosis in SH-SY5Y cells

“…Furthermore, the neuroprotective function of AA ameliorates MSG-induced cognitive deficits in vivo. The neonatal administration of MSG causes cognitive deficits in adult animals [50][51][52] . The Morris water maze is a commonly used method for evaluating learning and memory.…”

Broccoli sprout supplementation during pregnancy prevents brain injury in the newborn rat following placental insufficiency

“…Parameters measured include: ambulation (number of squares crossed), rearing (both forepaws leave the ground), grooming behavior, head lifting (lifting the head and neck in an exploratory manner) and defecation [19,22].…”