HISTAMINE DOES NOT PLAY AN ESSENTIAL ROLE IN ELECTROCORTICAL ACTIVATION DURING WAKING BEHAVIOR

Intraperitoneal injection of alpha-fluoromethylhistidine (alpha-FMH; 2 00 mg/kg), a specific inhibitor of histidine decarboxylase produced a severe depletion of neocortical and hippocampal histamine 3 h later as determined by a radioenzymatic assay. This treatment had no obvious e ffect on either low voltage fast activity (LVFA) in the neocortex or o n rhythmical slow activity (RSA) in the hippocampus during an 8 h reco rding period during the rats' light cycle. Scopolamine-sensitive LVFA, scopolamine-resistant LVFA and scopolamine-resistant hippocampal RSA all appeared unaffected. This suggests that any contribution histamine makes to electrocortical activation is probably indirect, acting via other transmitter systems.