Prenatal auditory enrichment with species‐specific calls and sitar music modulates expression of Bcl‐2 and Bax to alter programmed cell death in developing chick auditory nuclei

Abstract

Postnatal auditory stimulation influences early perceptual learning. Previously we reported morphological effects of prenatal auditory stimulation by species-specific and sitar musical sounds on the chick brainstem auditory nuclei-nucleus magnocellularis and nucleus laminaris. At hatching, these two nuclei of auditory enriched embryos showed higher neuronal numbers, amongst other morphological changes. There were also increases in synaptophysin and syntaxin1 expressions in the sound enriched groups and modulation of the developmental expression of transcription factors c-Fos and c-Jun. We hypothesized that prenatal auditory enrichment may have reduced embryonic apoptosis in these nuclei with possible alteration of molecular mechanisms enhancing the postsynaptic neuron's ability to survive. In the present study, therefore, we examined apoptotic cell death by TUNEL technique and Bcl-2 expression using immunohistochemistry and immunoblotting. In the controls, a peak percentage in the TUNEL-positive cells was noted in the auditory nuclei at embryonic day 12, which was reduced at embryonic day 16. Bcl-2 immunoreactivity decreased from embryonic day 8 to embryonic day 12 overlapping the period of embryonic cell death in these nuclei. The stimulated groups, however, showed fewer apoptotic neurons and higher Bcl-2 level than that in the controls. On the other hand, Bax immunohistochemistry showed correlated reverse changes compared to Bcl-2 expression. Thus prenatal extra-acoustic stimulation appears to alter Bcl-2 and Bax expression to support cell survival and differentiation, thereby augmenting the development of auditory nuclei.

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

“…This was followed by incubation in primary monoclonal antibodies (anti-synaptophysin, Sigma Chemicals, St Louis, Mo., USA; anti-PSD-95, Chemicon, USA) or polyclonal antibodies (anti-synapsin I, Chemicon) for 48 h in each case. After 3 washes, the sections were treated for 4 h with appropriate biotinylated secondary antibody and then in avidin-biotin-peroxidase complex (Vector Laboratories, Burlingame, Calif., USA) for 2 h. The binding sites of antigen-antibody interaction were visualized by a chromogen of 0.06% 3,3 -diaminobenzidine tetrahydrochloride and 0.15% NiSO 4 .…”

Prenatal acoustic stimulation influences neuronal size and the expression of calcium-binding proteins (calbindin D-28K and parvalbumin) in chick hippocampus

“…Early prenatal auditory enrichment by species-specific sound and sitar music in the domestic chick (Gallus domesticus) results in an increase in the number and size of neurons in two brainstem auditory nuclei: the nucleus magnocellularis (NM) and nucleus laminaris (NL) (Wadhwa et al, 1999). The enhanced sound stimulation favors the survival of neurons by reducing physiological cell death and increasing the relative amounts of Bcl-2, a anti-apoptotic protein (Alladi et al, 2005a). Prenatal patterned acoustic stimulation enhances synaptic protein synthesis (Alladi et al, 2002) and modulates the expression of the immediate early gene products, c-Fos and c-Jun, in NM and NL (Alladi et al, 2005b).…”

The Effect of Prenatal Auditory Enrichment on Perceptual Narrowing in Bobwhite Quail Neonates

“…Both auditory enriched groups displayed patterns of CREB and BDNF consistent with heightened learning and memory; however chicks were not subsequently tested behaviorally for a preference. The same protocol also yielded results indicating an increase in anti-apoptotic proteins, Bcl-2 and Bax, in auditory enriched groups; therefore auditory enriched groups had less neuronal death and increased differentiation of the auditory nuclei (Alladi, Roy, Singh, & Wadhwa, 2005A). Although chicks from the music enriched groups reflected many neurobiological benefits compared to controls, species-specific prenatal auditory enrichment had markedly stronger improvements compared to musical enrichment (Panicker, Wadhwa, & Roy, 2002).…”

“…As previously discussed, domestic chicken embryos receiving prenatal auditory enrichment in the form of complex sitar music showed a variety of neurological differences, including the expression of transcription factors associated with regeneration in the brainstem auditory nucleus (Alladi, Roy, Singh, & Wadhwa, 2005B) more complex hippocampal development (Chaudhury & Wadhwa, 2009;Wadhwa, Anand, & Bhowmick, 1998) and the presence of proteins associated with neural survival (Alladi, Roy, Singh, & Wadhwa, 2005A). Similarly, rat embryos that received music inutero demonstrated increased neurogenesis in the hippocampus as well as significantly better performance in tests of spatial ability and emotional reactivity (Kim et al, 2006).…”

“…Conversely, the abundant presence of ecologically invalid auditory stimuli, such as the electronic beeps of the machines found in the NICU environment, can have negative effects on language development in preterm human infants (Rand & Lahav, 2014). Further, in domestic chickens, the use of sitar music (ecologically invalid stimulation) as prenatal auditory enrichment has been shown to alter neurobiology associated with learning and memory (Alladi, Roy, Singh, & Wadhwa, 2005A;Chaudhury & Wadhwa, 2009); however during postnatal testing these enriched chicks demonstrated a preference for their species-typical call, no different from control chicks. Experiment 2 addressed how prenatal auditory enrichment, in the form of diverse and ecologically valid auditory stimulation would effect quail chicks' postnatal response to novelty.…”