Paternal Aggression in Early-Life Impairs the Spatial Memory and Passive Avoidance Learning in Adulthood of Male Rats: The Possible Role of DRD2

Negative early-life experiences (e.g., having an aggressive father) can leave long-lasting impacts on the behavior. However, it is not clear if they influence learning and memory. In this study, we investigated the influences that the presence of an aggressive father had on the level of passive avoidance learning and spatial memory. We also studied the changes in the dopamine receptor D2 (DRD2) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) gene expression in the hippocampus. Then, we evaluated if a DRD2 antagonist (Sulpiride, 0.125, 0.25, or 0.5 µg/rat) could modulate these changes. We found that the subjects exposed to early-life stress made by aggressive fathers had impaired passive avoidance learning and spatial memory than those with normal fathers. Treatment with Sulpiride improved passive avoidance learning and spatial memory in rats with aggressive fathers. The rats with aggressive fathers also had higher expression of the DRD2 gene in their hippocampus than those with normal fathers, while the PGC-1α gene expression was not different among groups. Treatment with Sulpiride (0.125, 0.25, or 0.5 µg/rat) reduced the DRD2 gene expression in those with aggressive fathers to the normal level in those with normal fathers. These data suggest that living in a shared place with an aggressive father, even without any physical contact, can detrimentally affect passive avoidance learning and spatial memory which is accompanied by the increased expression of the DRD2 gene. Also, Sulpiride as a dopaminergic antagonist could reverse this process.

Prenatal and early postnatal exposure to radiofrequency waves (900 MHz) adversely affects passive avoidance learning and memory

Prenatal and early postnatal are the most sensitive and high-risk periods to expose to electromagnetic fields (EMFs). This study aimed to investigate the effect of prenatal and early postnatal exposure to 900 MHz radiofrequency waves (RFWs) emitted from a base transceiver station antenna on passive avoidance learning and memory (PALM) and hippocampus histomorphology. Female Sprague Dawley rats (190–230 g) were paired with males. The mated rats, confirmed by observing a vaginal plug, were divided into two groups; control and exposed. The control group ( n = 7) was not exposed to RFW. The exposed group was divided into three subgroups ( n = 8); exposed Ⅰ, exposed during the gestational period (fetal life), and exposed Ⅱ and Ⅲ (postnatal exposure), exposed to RFW during the first 21 days of life, for 2 h/d and 4 h/d, respectively. PALM was evaluated by a shuttle box in 45-day-old pups. Learning and memory of animals were demonstrated as the duration of remaining within the light area, which is called the lighting time. Histological sections were prepared from brain tissues and stained with hematoxylin and eosin. An impairment in the PALM performance was noticed in all exposed subgroups (Ⅰ, Ⅱ, and Ⅲ) ( p < 0.05). Learning (short-term memory) and retention (long-term memory) behaviors were more affected in exposed subgroup Ⅰ (prenatal exposed) compared to other postnatal exposed subgroups (Ⅱ and Ⅲ). Also, a mild decrease in the density of pyramidal cells was observed in the hippocampus of exposed subgroups (Ⅰ and Ⅲ). Prenatal and early postnatal exposure to 900 MHz RFW adversely affected PALM performance and hippocampus tissue in rat pups with more impact for prenatal period exposure.

The protective effect of vitamin supplementation (E and E + C) on passive avoidance learning and memory during exposure to 900 MHz RFW emitted from BTS

Deleterious effects of exposure to electromagnetic radiation on public health have been widely studied. This study was conducted to evaluate the protective effect of vitamin supplementation (E or E + C) on passive avoidance learning (PAL) and memory in rats subjected to 900 MHz radiofrequency waves (RFW). Thirty adult male Sprague-Dawley rats (190 ± 20 g) were randomly divided into six groups as: control I (vehicle), control II (vitamin E 250 mg/kg), control III (vitamin E 100 mg/kg + l-ascorbic acid 200 mg/kg), and three exposed groups to RFW as: sham-exposed, treatment I (vitamin E), and treatment II (vitamin E + C). The duration of exposure was 30 continuous days (4 h/day). The PAL was evaluated on the last day by the shuttle box. Learning and memory of animals demonstrated as the duration of remaining within the light area, which is called the light time (LT). The sham-exposed group showed a significant decrease in LT on the learning, consolidation, and retention days compared to other groups ( p < 0.05). Pretreatment with vitamins (E and E + C) could protect PAL against adverse effects of RFW, and the administration of vitamin E + C improved PAL performance in control III compared to control I and treatment II groups ( p < 0.05). Administration of vitamin E + C to exposed group (treatment II) caused a significant increase in LT on the learning ( p = 0.013), consolidation, and retention ( p = 0.009) sessions compared to the treatment group I (vitamin E). Long-term exposure to 900 MHz RFW impaired PAL and memory, and pretreatment of vitamin (E or E + C) prevented these effects, which may be a new potential mechanism against side effects of RFW.