Effect of physostigmine and atropine on the single-trial passive avoidance response in rats.

Rats received a single training trial on an inhibitory avoidance (passive avoidance) task and retention trials 24 hr (R-I) and 48 hr (R-II) later, in a special two-chambered apparatus, and the mean step-through latency was determined. The animals were given the drug, either pre-trial, pre-trial plus pre-retention, pre-retention or post-trial. Physostigmine (0.1 mg/kg, ip) and atropine (6.0 mg/kg, ip) had no effect on learning, but they adversely affected retention, particularly at 24 hr. The effect seems to involve central cholinergic mechanisms of retention.

Effect of propranolol and phenoxybenzamine on muscle strength and physical endurance, and on exercise-induced changes in muscle glycogen and blood lactic acid levels in rats.

Propranolol and phenoxybenzamine (PBZ) had no major effect on swimming-endurance performance and skeletal muscle pulling-strength in rats. Propranolol, like exercise itself diminished the resting skeletal muscle glycogen (SMG) content, but the drug did not lower the resting blood lactic acid (BLA) levels. Propranolol significantly antagonised the 25-min exercise-induced BLA elevation, indicating that lactacidaemia is possibly a beta-receptor response. However, propranolol did not exhibit an overall beneficial effect on swimming endurance. PBZ had a negligible effect on maximal swimming time (MST) and had no major effects on the SMG content and BLA levels.