CENTRAL NICOTINIC RECEPTOR BLOCKADE INHIBITS EMOTIONALLY CONDITIONED PRESSOR-RESPONSES IN RATS

A conditioned stimulus previously paired with electric footshock produ ced an increase in blood pressure in conscious, freely moving rats. Th e conditioned presser response was reproducible. Intracerebroventricul ar injection of the nicotinic receptor antagonists hexamethonium (1-10 mu g) or pentolinium (10 mu g) but not the muscarinic receptor antago nist methylatropine (3 mu g) produced an inhibition of the conditioned presser response, whereas intraarterial injection of hexamethonium (1 0 mu g) did not affect the response. Intraventricular injection of the cholinesterase inhibitor physostigmine (3-10 mu g) produced an enhanc ement of the conditioned presser response. These results are consisten t with the possibility that central nicotinic receptors play a role in the expression of the emotionally conditioned presser response in rat s.