Anxiolytic effect of kynurenic acid microinjected into the dorsal periaqueductal gray matter of rats placed in the elevated plus-maze test.

The effect of kynurenic acid (20 to 160 nmol) microinjected into the dorsal periaqueductal gray matter was measured in rats placed in an elevated plus-maze. Microinjection of 160 nmol of kynurenic acid increased the percentages of open arm entries and of time spent in the open arms. Both of these measures may be considered indexes of anxiolysis. Although kynurenic acid also increased the total number of entries, analysis of covariance shows that the increase in open arm entries is independent of the effect on closed arm entries. Thus, the anxiolytic effect of kynurenic acid detected in the elevated plus-maze strengthens the proposal that glutamatergic neurons of the dorsal periaqueductal gray matter play an important role in anxiety.