Low atropine dose increases the frequency of hippocampal theta activity

The influence of two doses (6 and 3mg/kg) of atropine (A) on hippocampal theta activity (TA) induced by means of reticular stimlulation was studied in waking rats with implanted electrodes. The higher dose of A depressed TA and the lower dose reduced markedly its incidence. The frequency of TA remaining after A administration increased significantly. The results suggest that A acts in a different way upon the mechanisms responsible for the occurrence of TA and its frequency. An accidental finding was that' A prolongs paroxysmal hippocampal EEG -induced by reticular stmimulation.