Some Eifects of Muscarinic Cholinergic Blocking Drugs on Behavior and the Electrocorticogram* By

A persisting enigma is the fact that eholinergic blocking drugs cause a "dissociation " between electroencephalographie (EEG) activity and gross behavior (BRADLEY and ELKES 1957; WIKLV, ~ 1952). Although these drugs produce EE G's typical of somnolence orcoma, gross behavior is apparently unaltered. This finding has led to attempts to determine more precisely defined behaviors which are affected by cholinergic blocking drugs. One of the most intriguing findings is that these agents markedly impair the acquisition, but not the retention, of learned behaviors (HE~z 1960; M~CRELSO ~ 1961). HERZ suggested that this dichotomous effect results from a disturbance of recent memory. Indeed, adequate doses of atropine (MIGDAL and F~v~I ~ 1963; OSTF~LD et al. 1960) and scopolamine (GooDMAN and GILMA ~ 1955) cause recent memory loss in man. The fact that eholinergic blocking drugs may cause a recent memory loss prompted us to replicate the findings of I-I~z using scopolamine and the more active isomer of atropine, 1-hyoscyamine. In addition, the effects of these agents on spontaneous electrocortical ctivity and on spontaneous p ychomotor activity were studied in an effort to clarify some of the relevant variables. For purposes of clarity the data will be presented as four separate xperimental section. Experiment I The effects of cholinergic blocking drugs on the acquisition of a conditioned avoidance response Methods. Eighty-four male rats (]=Ioltzmann), ranging from 48 to 62 days of age, served as the subjects. They were randomly assigned, with the restriction of equal numbers, to 7 groups receiving 0.13 o