Unilaterally activated systems in rats self-stimulating at sites in the medial forebrain bundle, medial prefrontal...

Rats with electrodes in either the posterior medial forebrain bundle (MFB), the anterior MFB, the medial prefrontal cortex, or the locus coeruleus self-stimulated during a 45 min period following the injection of [14C]2-deoxyglucose. They were then sacrificed and their brains prepared for autoradiography. The autoradiographs were analyzed for unilaterally activated neural systems, using a computerized image analyzing system to compare the darkness of neural structures on the stimulated side with the darkness of the same structures on the unstimulated side. There was extensive overlap in the neural structures unilaterally activated by stimulation in the anterior and posterior MFB; but there was no overlap between the structures activated by MFB stimulation and the structures activated by stimulation at either of the extradiencephalic sites; nor did the forebrain, diencephalic, and midbrain sites have any readily apparent bilateral effects in common. If there is a substrate common to MFB self-stimulation and extradiencephalic self-stimulation, its activation is not revealed by 2-deoxyglucose autoradiography.