Sleep modifies glutamate decarboxylase mRNA within the barrel cortex of rats after a mystacial whisker trim.

STUDY

OBJECTIVES

Determine the effects of time of day and sleep deprivation on glutamate decarboxylase 67,000 MW (GAD67) mRNA during cortical synaptic reorganization induced by a unilateral trimming of the mystacial vibrissae in rats.

DESIGN

Two experiments were conducted--One measured GAD67 mRNA in the barrel cortex at 3 or 6 h after a unilateral whisker cut at either light or dark onset; the other measured GAD67 mRNA after a unilateral whisker cut at light onset with or without sleep deprivation.

SETTING

University-based Research Laboratory.

PARTICIPANTS

Sprague-Dawley rats (250-350 g).

INTERVENTIONS: N/A.

MEASUREMENTS AND

RESULTS

The reverse transcriptase polymerase chain reaction was used to measure the time of day changes in GAD67 mRNA after a unilateral whisker cut. GAD67 mRNA decreased in the barrel cortex at 3 and 6 h after a whisker trim at dark onset when the rats were mainly awake. No changes were observed in GAD67 mRNA levels after a whisker cut at light onset, a time when the rats mainly sleep. In situ hybridization for GAD67 mRNA supported these findings; no changes in GAD mRNA occurred in layer 4 of the barrel cortex that received input from the mystacial whiskers that were trimmed at light onset. However, when the rats were sleep-deprived, GAD67 mRNA increased in the barrel cortex receiving input from the lip hairs surrounding the trimmed mystacial whiskers.

CONCLUSIONS

These data imply that sleep modifies GAD67 mRNA expression and that this effect is dependent upon the nature of the ongoing synaptic reorganization. They support the notion that sleep serves a synaptic function.