Stereotaxic preparation of circumscribed cortical areas from rat brain for biochemical studies

A method for the rapid dissection of circumscribed areas of rat cortex is described. The technique does not depend on skull-derived landmarks but uses for stereotaxic orientation the cross-point of the interhemispheric gap with the caudal margin of the cortex. An application of this dissection method to the biochemical analysis of cholinergic markers within the hindlimb representation of the primary somatosensory cortex revealed that both the activity of the enzyme choline acetyltransferase as well as the binding of [3H] quinuclidinyl benzilate to muscarinic cholinergic receptors do not seem to be affected drastically three days after unilateral transection of the sciatic nerve. The only significant effect detected was a slight decrease in the activity of the choline acetyltransferase within the hindlimb representation of the primary somatosensory cortex contralateral to the transected sciatic nerve. In the primary visual cortex, the cholinergic markers investigated did not show significant alterations after sciatic nerve injury.