Changes in neuromodulatory effect of adenosine A1 receptors on piriform cortex field potentials in amygdala kindled rats.

Adenosine exerts its anticonvulsants effect through different brain regions including piriform cortex. In this study, the effect of amygdala kindled seizures on adenosine A1 receptor-mediated neuromodulation in piriform cortex pyramidal neurons was tested at 24 h and 1 month after kindling. Animals were kindled by daily electrical stimulation of amygdala. Field potentials were recorded from layer II of piriform cortex pyramidal cells following stimulation of the lateral olfactory tract. Obtained results showed that N6-cyclohexyladenosine (CHA), a selective adenosine A1 receptor agonist (1, 10 and 100 microM; i.c.v.), reduced A1 slope and B1 amplitude of field potentials in both kindled and non-kindled (control) rats. However, its effects on kindled animals were more potent at 24 h, but not 1 month post-kindling. 8 cyclopenthyl-1,3-dimethylxanthine (CPT), a selective adenosine A1 receptor antagonist (50 microM, i.c.v.), had no significant effect on the field potential parameters. However, CPT (50 microM, i.c.v.) pretreatment eliminated effects of CHA (10 microM; i.c.v.) on the field potentials. These results indicate that activation of adenosine A1 receptors has an inhibitory effect on the field potentials of piriform cortex pyramidal neurons and the efficiency of adenosine A1 receptor neuromodulation in piriform cortex is increased at short-term (24 h) but return to normal at long-term (1 month) after kindling implementation.