Possible Involvement Of Cholinergic System Research Articles

P01-432 - Effects of cholinergic system of dorsal hippocampus of rats in the MK801-induced anxiolytic-like behavior

IntroductionSome investigations showed that the glutamate receptors have critical role for cognition such as learning and anxiety in the brain.ObjectivesThe possible involvement of cholinergic system of dorsal hippocampus in the anxiolytic-like response induced by NMDA receptor antagonist, MK801 has been investigated in the present study.MethodsThe male wistar rats were used and the elevated plus maze apparatus has been used to test parameters (%OAT, %OAE, locomotor activity, grooming, rereading and defection) of anxiety-like behaviors.ResultsThe data indicated that intra-CA1 administration of MK801 (2 μg/rat) increased %OAT and %OAE but did not other exploratory behaviors, indicating an anxiolytic-like response. Moreover, intra-hippocampal injection of cholinergic receptor antagonists, mecamylamine (2 μg/rat) and scopolamine (4 μg/rat) by itselves, 5 min before testing increased %OAT and %OAE, but did not alter locomotor activity and other exploratory behaviors, suggesting anxiolytic-like behavior. On the other hand, intra-CA1 co-administration of ineffective doses of scopolamine (3 μg/rat), but not mecamylamine (1 μg/rat) with ineffective dose of MK801 (1 μg/rat) increased %OAT and %OAE.ConclusionThe data may indicate that the possible involvement of cholinergic system of CA1 on anxiolytic-like response induced by MK801.

Effect of vitamin E on memory retention in rats: Possible involvement of cholinergic system

This study concerned effects of vitamin E and the cholinergic system on memory retention of passive avoidance learning in rats. Post-training intracerebroventricular (i.c.v.) injections were carried out in all experiments. Administrations of vitamin E (10, 25 and 50 μg/rat), nicotine (0.1 μg/rat) and pilocarpine (0.5 μg/rat), the muscarinic receptor agonist increased memory retention, while mecamylamine (0.01, 0.1 and 0.5 μg/rat), the nicotinic receptor antagonist and scopolamine (0.1, 1 and 5 μg/rat), the muscarinic receptor antagonist decreased memory retention. The combination of vitamin E with nicotine or pilocarpine showed potentiation. Effects of mecamylamine or scopolamine were attenuated by vitamin E. It is concluded that vitamin E has a close interaction with cholinergic system in memory retention process.

Reversal of morphine-induced memory impairment in mice by withdrawal in Morris water maze: possible involvement of cholinergic system

The effects of morphine and morphine withdrawal on memory performance were examined in mice by using Morris water maze task. Morphine-induced memory impairment at the doses of 5 and 10 mg/kg recovered after repeated administration. Oxotremorine, a muscarinic receptor agonist, at the dose of 0.1 mg/kg ip, and physostigmine, a cholinesterase inhibitor, at the dose of 0.1 mg/kg ip, significantly antagonized morphine (10 mg/kg sc)-induced memory impairment in mice. Furthermore, repeated naloxone (0.5 mg/kg ip) attenuated scopolamine (0.2 mg/kg ip)-induced memory impairment. By using escalating doses of morphine for 13 days, morphine-induced memory impairment was continuously maintained. When withdrawal was precipitated by naloxone (5 mg/kg ip), or administration of oxotremorine (0.1 and 0.2 mg/kg ip) or physostigmine (0.05 and 0.1 mg/kg ip), the impairment was completely reversed. These results suggest that morphine-induced memory impairment could be partially due to the inhibition of the central cholinergic activity.