BELLADONNA ALKALOIDS-INDUCED BEHAVIORAL-CHANGES AND AMNESIA ON OPEN-FIELD AND STEP-THROUGH IN 18, 28, AND 38-DAY-OLD MICE

AIM: To study the age-related changes of atropine (Atr), scopolamine ( Sco), anisodine (AT(3)), and anisodamine (Ani) on behaviors and memori es. METHODS: The behaviors and memories were measured with open-field test and step-through task. M-cholinergic receptors were determined by [H-3] quinuclidinyl benzilate ([H-3] (QNB). RESULTS: During acquisiti on session (d 1) the 18, 28-, and 38- d-old mice pretreated with Atr, Sco, and AT(3)(0.02, 0.2, 2, or 20 mg . kg(-1), ip) in open-field test showed increase in walking counts by 26% - 42%, but decrease in reari ng, grooming, and defecating counts for 50% - 92%, 67% - 100%, and 75% - 100%, respectively. On recall session (d 2) the walking and reaping behaviors in the 18- and 28-d-old nice receiving Atr, Sco, and AT(3) on d 1 were higher than those in the mice receiving saline. But a lowe r grooming behavior on d 2 was found in the mice receiving the drugs o n d 1, On d 1 Ani 20 mg . g(-1) reduced the rearing behavior by 50% in 18-d-old mice and defecation by 33% - 36% in 18- and 28-d-old mice. A ll the 4 belladonna alkaloids increased the number of avoidance-respon se errors and decreased the retention latencies in step-through task. B-max of [H-3]QNB binding sites in frontal cortex and hippocampus regi ons in the 38-d-old mice increased 7% and 23% vs in the mice of 18 d o f age, respectively. CONCLUSIONS: 1) The effects of the belladonna alk aloids on behaviors and memories in adult mice were weaker than those in young mice. 2) The belladonna alkaloids-induced amnesia on passive avoidance-response in step-through was more sensitive than behavioral changes and amnesia on open-field. 3) According to the lowest effectiv e doses which insulted the behaviors or memories in young mice, Sco wa s about 10, 100, and 1000 times more potent than Atr, AT(3), and Ani, respectively.