Expression of Synaptic Proteins in the Hippocampus and Spatial Learning in Chicks following Prenatal Auditory Stimulation

Abstract

Prenatal auditory stimulation by species-specific sound influences the expression and levels of calcium-binding proteins in the chick hippocampus, which is important to learning and memory. Stimulation by sitar music additionally produces structural changes in the hippocampus. Synapse density, which influences the synaptic plasticity, is also increased following both types of sound stimulation. Here we report the expression of mRNA as well as levels of synaptic proteins (synaptophysin, synapsin I and PSD-95) in the hippocampus of developing chicks subjected to prenatal auditory stimulation. Further, to evaluate the behavioral outcome following acoustic stimulation, posthatch day 1 (PH1) chicks were analyzed by T-maze test for spatial learning. Fertilized zero day eggs were incubated under normal conditions and subjected to patterned sounds of species-specific or sitar music at 65 dB levels for 15 min/h over 24 h at a frequency range of 100–6,300 Hz for a period of 11 days from embryonic day (E) 10 until hatching. Following both types of prenatal acoustic stimulation, a significant increase in the levels of synaptophysin mRNA and protein was found from E12, whereas that of synapsin I and PSD-95 was observed from E16, suggesting early maturation of the excitatory synapse. A significant decrease in the time taken to reach the target over the 3 trials in both sound-stimulated groups indicates improved spatial learning. In the music-stimulated group, however, the time taken to reach the target was reduced from the very first trial, which may point to an involvement of other behavioral attributes in facilitating spatial navigation.

Activation of Glycogen Synthase Kinase-3 Mediates the Olfactory Deficit-Induced Hippocampal Impairments

“…We also found that OBX reduced the levels of synapsin I, synaptophysin, NR2A/B, and PSD95. Studies have demonstrated that alterations of postsynaptic spine density and morphologies actively participate in learning and memory processes [46,74,75], and the reduction of these preand postsynaptic proteins can directly damage the synaptic transmission and thus cause memory deficits [76,77].…”

Prenatal Loud Music and Noise: Differential Impact on Physiological Arousal, Hippocampal Synaptogenesis and Spatial Behavior in One Day-Old Chicks

“…Sections were then incubated in primary antibodies: anti-synaptophysin and anti-PSD 95 (dilution: 1∶500, mouse monoclonal, Chemicon, Millipore, CA, USA) for 48 hrs at 4°C. The cross reactivity of the antibodies to chick brain epitopes has been shown earlier in another study [18]. After three washes, the sections were treated with biotinylated secondary antibody (dilution: 1∶200, anti-mouse, Vector laboratories, Burlingame, CA, USA) for 24 hr at 4°C and then in avidin-biotin-peroxidase complex (Vectastain Elite Kit, Vector Laboratories, Burlingame, CA, USA) for 2 hr.…”

“…Early maturation of the auditory system [13]–[15] and the development of species typical perceptual preference is observed in birds following exposure to species own typical call [16], [17]. Our previous studies showed improved morphological and biochemical changes in chick hippocampus and facilitation of spatial orientation and learning at 12 hour post hatch consequent to prenatal sound stimulation by species-specific calls and sitar music at 65 dB [18]–[21]. The facilitation of learning was observed even at 24 hour post hatch with no further improvement in successive trials following the same sound enrichment protocol suggesting an early maturation of synaptic connectivity following prenatal sound stimulation.…”

Prenatal Complex Rhythmic Music Sound Stimulation Facilitates Postnatal Spatial Learning but Transiently Impairs Memory in the Domestic Chick

“…Prenatal as well as postnatal auditory enrichment has been shown to enhance spatial learning and the neural substrates responsible for learning in the hippocampus of rats and mice [Kim et al, 2006;Xu et al, 2009]. In chicks, prenatal sound stimulation with either species-specific or music sounds significantly increased the expression of calcium binding proteins, neuronal size and mean synaptic density in the chick hippocampus and facilitated spatial learning at 12 h posthatch [Chaudhury et al, 2006[Chaudhury et al, , 2009[Chaudhury et al, , 2010. We observed a significant facilitation in learning at 24 h posthatch in the sound-stimulated groups, although significant only in the species-specific group, following which there was no further improvement.…”

“…Morphologically, an increase in the neuron number, size of neuronal nuclei, glial numbers and expression of synaptic and calcium binding proteins in nucleus magnocellularis and nucleus laminaris of the chick brainstem auditory nuclei are observed following prenatal exposure of the developing embryos to both species-specific calls and music sounds [Alladi et al, 2002;Panicker et al, 2002]. Enhanced neural substrate in the hippocampus and facilitation of spatial learning at 12 h is also observed following prenatal auditory stimulation with species-specific calls as well as music sounds in chicks [Chaudhury et al, 2010]. However, the effect of prenatal sound stimulation on long-term memory is not clear.…”