Effect of NG-nitro-L-arginine methyl ester a nitric oxide synthase inhibitor on neurotransmitter receptor systems in aged rats

In order to examine the effect of age and nitric oxide synthase inhibitor N^G-nitro-L-arginine methl ester (l -NAME) we studied the changes on major neurotransmitter receptor systems in 6 (adult and 24-month-old (aged) Fischer male rats using receptor autoradiography. l -name was administrated intraperitoneally in aged rats once a day for 4 weeks. ³H]QNB (quinuclidinyl benzilate) ³HC (hemicholinium-3) ³H] muscimol ³H] SCH 23390 (N-methyl-³H] N-methyl-³H]R+]-8-chloro-2 3 4 5-tetrahydro-3-methyl-5-phenyl-7-il-benzazepine) ³H] mazindol were used as markers of muscarinic acetylcholine receptors high-high-affinity choline uptake sites GABA_A (γ-aminobutyric acid (SP2)_A) receptors dopamine D₁ receptors dopamine D₂ receptors and dopamine uptake sites respectively. The age-related change in ³H muscimol binding in the brain was more pronounced than that in ³H] QNB ³H]HC ³H]SCH 23390 ³H] nemonapride and ³H] nemonapride and ³H] mazindol binding.Chronic treatment (4 weeks) with l -NAME caused no significant changes in sp1)³H] muscimol ³H SCH 23390 and ³H] nemonapride binding in most areas of aged rat brain as compared with vehicle-treated aged animals. However chronic treatment with l -NAME caused a significant reduction in ³H] HC and ³H] mazindol binding in any brain regions of aged rats in comparison with the vehicle-treated aged animals. These results demonstrate that the GABAergic system is more susceptible to aging processes than cholinergic and dopaminergic systems in teh brain. Furthermore our findings suggest that nitric oxide may play some role in the regulation of choline uptake and dopamine uptake systems during aging processes.