Neuronal Histamine Systems and Behavior

Histamine-Alvarez

Dear Dr. Alvarez,
Your results showing that histamine injections into the hippocampus inhibited avoidance learning and was blocked by pyrilamine is of high interest to us since we showed (unpublished) that post-trial injection of H1 blocker chlorpheniramine <8but not the H2 blocker ranitidine) into the ventral pallidum (possibly cholinergic cells) facilitated inhibitory avoidance learning. Chlorpheniramine injection into both the ventral pallidum and nucleus accumbens was found to be reinforcing in a place preference task.
On the other hand, your finding that injecting histamine into the nucleus accumbens has anxiogenic effects seems to be contrary to some of our data, which show, 1) that chronic infusion of chlorpherinamine into the ventricles is anxiolytical, and 2) that ventral pallidum infusion of both chlorpherinamine (0.1 and 20ug) as well as ranitidine (20ug) proved to be anxiolitic using the elevated plus maze. Any ideas to this? Regards Joe Huston

Thu Dec 10