Cardiovascular response to the injection of acetylcholine into the anterior cingulate region of the medial prefrontal cortex of unanesthetized rats

Injection of acetylcholine (ACh) (2.5-60 nmol) into the anterior cingulate cortex caused dose dependent hypotensive responses (E-max = -25.3 mmHg) and no change in the heart rate. The hypotensive response to 30 nmol of ACh wa s blocked by local pretreatment with atropine (3 nmol) or 4-DAMP (6.7 nmol) , a non-tropine muscarinic antagonist. When the same dose of atropine was i njected i.v., no changes were observed in the hypotensive response to intra cortical ACh. This observation rules out the possible leakage of ACh into t he peripheral circulation and favors the idea of a cortical site of action. The injection of the same dose of ACh into the corpus callosum or the occi pital cortex did not cause changes in the cardiovascular system. The presen t results confirm earlier evidence that the cingulate cortex is involved in the control of the autonomic system and indicate that cholinergic muscarin ic receptors in the cingulate cortex mediate a hypotensive response without a change in heart rate.