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Effects of alcohol on functional development of the auditory pathway in the brainstem of infants and chick embryos
Insights
Alcohol exposure during development disrupts auditory brainstem function in infants and chick embryos. Early alcohol effects on neural pathways may contribute to fetal alcohol syndrome handicaps.
Area of Science:
- Neuroscience
- Developmental Biology
- Toxicology
Background:
- Prenatal alcohol exposure is a leading cause of preventable birth defects.
- Fetal Alcohol Syndrome (FAS) is associated with cognitive and behavioral deficits.
- The impact of alcohol on developing auditory pathways is not fully understood.
Purpose of the Study:
- To investigate the effects of alcohol on the developing auditory brainstem.
- To examine functional and structural changes in the auditory pathway due to prenatal alcohol exposure.
Main Methods:
- Auditory brainstem evoked responses (ABRs) were recorded in human neonates exposed to alcohol in utero.
- Neurophysiological and histological studies were conducted on chick embryos exposed to alcohol during early incubation.
- Golgi impregnation and electrical stimulation were used to assess neuronal structure and function.
Main Results:
- Four out of six infants exposed to alcohol showed abnormal auditory brainstem evoked responses.
- Chick embryos exposed to alcohol exhibited normal neuroanatomical arrangement but abnormal dendritic structure.
- Abnormalities in synaptic function and nerve terminal distribution were observed in alcohol-exposed chick embryos.
Conclusions:
- Alcohol exposure during critical developmental periods disrupts the functional maturation of the auditory brainstem.
- Early-onset auditory pathway alterations may underlie some behavioral and intellectual impairments seen in fetal alcohol syndrome.
- This research highlights the vulnerability of the developing auditory system to alcohol teratogens.
Abstract:
The effects of alcohol on the development of neural function in the auditory pathway of the brainstem have been examined in human neonates and chick embryos. Auditory brainstem evoked responses were recorded in six infants of mothers for whom there was evidence of alcohol abuse during pregnancy. In four of the infants, evoked responses were abnormal, with poorly defined, inconsistent peaks. Neurophysiological and histological studies were done on chick embryos which received a single dose of alcohol early incubation. In most surviving embryos the neuroanatomical arrangement of the auditory nuclei in the brainstem was normal. However, Golgi impregnation revealed abnormalities in the length and structure of the dendrites in nucleus laminaris. Electrically evoked neuronal activity revealed abnormalities of synaptic function and the distribution of nerve terminals. The results indicate that in infants and chick embryos the functional development of the auditory pathway in the brainstem is disrupted by exposure to alcohol. Such early changes in this sensory pathway may contribute to the behavioural and intellectual handicaps associated with the fetal alcohol syndrome.