THE SUPPRESSION OF LONG-TERM POTENTIATION IN RAT HIPPOCAMPUS BY INHIBITORS OF NITRIC-OXIDE SYNTHASE IS TEMPERATURE AND AGE-DEPENDENT

At room temperature (23-degrees-C-25-degrees-C), the induction of long-term potentiation (LTP) in area CA1 of slices from young male Sprague-Dawley rats was depressed by preincubation with the nitric oxide synthase inhibitors N(G)-nitro-L-arginine (L-NA, 100 muM) and N(G)-nitro-L-arginine methyl ester (L-NAME, 100 muM). The D isomers were ineffective under the same conditions. Hemoglobin (20 muM) reduced but did not completely block LTP. Neither L-NA (at concentrations up to 1 mM) nor hemoglobin (20 muM) had any significant effect on LTP in slices from adult rats at room temperature, or in young rats at 29-degrees-C-30-degrees-C. These results suggest that nitric oxide is unlikely to play a role in the induction of LTP under physiological conditions.