An environment-dependent modulation of cortical neural response by forebrain cholinergic neurons in awake rat.

The forebrain cholinergic neurons project to cortex, including the hippocampus and the cingulate cortex (Cg). However, the relative influence of these neurons on behavior-linked neural processing in the two cortical areas remains unclear. We have now examined the effect of destruction of the cholinergic neurons with microinjection of the immunotoxin 192 IgG-saporin into the medial septum on the induction of c-Fos protein, an index of neuronal synaptic excitation, in the two forebrain areas to varied episodic experiences.

Nociception-driven decreased induction of Fos protein in ventral hippocampus field CA1 of the rat.

To test the hypothesis that the hippocampus field CA1 is recruited in nociceptive intensity-dependent fashion in the formalin model of inflammatory pain, we determined the effect of injection of formalin (0.625-2.5%) on the induction of Fos protein along the length of the hippocampus.