Investigation into the effects of prenatal alcohol exposure on postnatal spine development and expression of synaptophysin and PSD95 in rat hippocampus

Abstract

Ethanol is known as a potent teratogen responsible for the fetal alcohol syndrome characterized by cognitive deficits especially pronounced in juveniles but ameliorating in adults. Since the mechanisms of these deficits and following partial recovery are not fully elucidated, the aim of the present study was to investigate the process of synaptogenesis in the hippocampus over the first two months of life in control and fetal‐alcohol rats. Ethanol was delivered to the pregnant dams by intragastric intubation throughout 7–21 gestation days at the daily dose of 6 g/kg generating a mean blood alcohol level of 246.6 ± 40.9 mg/dl on gestation day 20. The spine densities as well as the expression of pre‐ and postsynaptic proteins, synaptophysin (SYP) and PSD‐95 protein, were evaluated for three distinct hippocampal regions: CA1, CA2+3, and DG and four postnatal days: PD1, PD10, PD30 and PD60, independently. Our results confirmed an intensive synaptogenesis within the brain spurt period (first 10 postnatal days), however, the temporal pattern of changes in the SYP and PSD‐95 expression was different. The ethanol exposure during half of the 1st and the whole 2nd human trimester equivalent resulted in an overall trend toward lower values of synaptic indices at PD1 with a fast recovery from these deficits observed already at PD10. At PD30, around the age when the most pronounced behavioral deficits have been previously reported in juvenile fetal‐alcohol subjects, no significant changes were found in either the hippocampal levels of synaptic proteins or in the spine density in principal hippocampal neurons.

Effects of prenatal binge‐like ethanol exposure and maternal stress on postnatal morphological development of hippocampal neurons in rats

“…Adult, naive, female (n = 50) and male (n = 15) Wistar rats, obtained from the Animal Breeding Facility of the Gülhane Military Medical Academy (Ankara), were initially used for breeding. The animals’ maintenance conditions during breeding and rearing were the same as in our previous studies (Dursun et al, 2006; Elibol‐Can et al, 2014a,b). Rats were allowed to mate until a vaginal plug, an evidence of a successful fertilization, was observed.…”

“…Starting from the GD7 throughout GD20, dams from A group were daily administered 6 g ethanol (96.5% v/v, Merck) per kg body weight by intragastric intubations using a stainless, curved feeding needle (18 ga, 3 in, Stoelting Co., Wood Dale, IL). The alcohol solution was prepared daily as a 25% (vol/vol) ethanol mixed with distilled water which was divided into two equal doses given to animals 1 h apart (Dursun et al, 2006; Elibol‐Can et al, 2014a,b). Animals in IC group received the same volume of fluid with sucrose substituted isocalorically for ethanol.…”

“…In order to exclude sex as an additional independent variable in the data analysis, in this study, we used only the male subjects (Dursun et al, 2006; Elibol‐Can et al, 2014a,b). Male pups belonging to the mothers from each of treatment groups were randomly assigned to 4 age sub‐groups sacrificed at birth (PD1) (n = 87), at the end of the brain growth spurt period (PD10) (n = 88), after weaning at the juvenile age (PD30) (n = 90), and as young‐adults (PD60) (n = 90) with 7–8 pups per each treatment/age group.…”

“…In these studies, a moderate prenatal intoxication with ethanol showed a mild effect on hippocampal development limited to a marginally lower number of granular cells in DG on postnatal day (PD) 30 which correlated with a trend towards a lower count of DCX‐immunoreactive neurons in subgranular zone at PD10 (Elibol‐Can et al, 2014a). At PD30, around the age when the most pronounced behavioral deficits have been previously reported in juvenile fetal‐alcohol subjects, no significant changes were found in the levels of synaptic proteins in either cornu ammonis (CA) or dentate gyrus (DG) of the rat hippocampus (Elibol‐Can et al, 2014b). In the present study, we attempted to examine whether behavioral deficits and the following functional recovery previously observed in the juvenile fetal‐alcohol subjects (Dursun et al, 2006; Elibol‐Can et al, 2014a) may be due to some other subtle plastic changes within the hippocampal formation such as abnormalities in cellular morphology, which is known to be important for establishment of network connectivity and activity patterns (Krichmar et al, 2002; Schaefer et al, 2003).…”

Reduced density of dendritic spines in pyramidal neurons of rats exposed to alcohol during early postnatal life

“…Cui et al (2010) have demonstrated a decrease in the number of dendritic spines for layer 5 (L5) PNs in the primary visual cortex, after prenatal exposure to alcohol. Other studies have demonstrated a decreased spine density or an alteration of spine development in the hippocampus after early exposure to alcohol (e.g., Berman and Hannigan, 2000; Elibol‐Can et al, 2014). The reduced spine density has been also observed after alcohol treatment of primary cultures of hippocampal neurons and has been attributed to alterations of the actin cytoskeleton (Romero et al, 2013).…”