Re: Effect of Ultrasound during fetal period on learning and memory

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Effect of diagnostic ultrasound during the fetal period on learning and

memory in mice

R. Suresh, a, , T. Ramesh Raoa, E.M. a, Nikolai Ovchinnikova and

A. Mc Raea

ls of Anatomy - Anatomischer Anzeiger

Article in Press, Corrected Proof

Background

An experiment was conducted to find out whether in utero exposure to

diagnostic ultrasound leads to changes in postnatal behavior in adult

mice.

Methods

A total of 15 pregnant Swiss albino mice were exposed to diagnostic

levels of ultrasound (3.5 MHz, 65 mW/cm2, intensity(spatial

peak & #8722;temporal peak) (ISPTP)=1 mW/cm2, intensity(spatial

average & #8722;temporal average) (ISATA)=240 mW/cm2) for 30 min on day 14 or

16 of gestation. All exposed as well as control animals were left to

complete gestation and parturition. Their offspring were used in our

further studies. They were monitored during early postnatal life for

standard developmental markers (such as pinna detachment, eye opening

and fur development) and postnatal mortality was recorded up to 6

weeks of age. The litters were subjected to behavioral tests for

learning and memory at 4 months of age. Representative animals from

each group were sacrificed and the hippocampal region of the brain

was assayed for biogenic amines, noradrenaline, dopamine, serotonin

(5-HT) and 5-HT's metabolite, 5-hydroxy indoleacetic acid (5-HIAA),

in order to determine whether ultrasound exposure produced any

biochemical changes in the hippocampal region of the brain. Coronal

sections from the dorsal hippocampus from the representative animals

from each group were processed for staining and the number of neurons

was counted.

Results

Neither the standard developmental markers (such as pinna detachment,

eye opening and fur development) nor the postnatal mortality was

affected by ultrasound exposure. However, there was a significant

impairment in learning (hole board test) and memory functions

(shuttle box test) in both the exposure groups. Significant

reductions in the biogenic amines and the decrease in the neuronal

density were found only in day 14th pc ultrasound-exposed group

compared with the control animals. The 16th day exposure group is

relatively resistant to ultrasound-induced impairment of brain

functions.

Conclusions

The results suggest that the early fetal brain is highly susceptible

to induction of neurobehavioral changes by ultrasound exposure.

Keywords: Behavior; Gestation; Ultrasound; Neurotoxicity

Corresponding author. Tel.: +1 868 645 2640x4627(Off.)/1 868 645

2640x1863(Res.); fax: +1 868 662 9148.

Anatomy and Cell Biology Unit, Department of Preclinical Sciences,

Faculty of Medical Sciences, The University of The West Indies, St.

Augustine, Trinidad and Tobago, West Indies

Received 9 January 2007; accepted 13 May 2007. Available online 23

October 2007.

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