Modulatory effects of adenosine on inhibitory postsynaptic potentials in the lateral amygdala of the rat

1 Adenosine is a depressant in the central nervous system with pre- and pos tsynaptic effects. In the present study, intracellular recording techniques were applied to investigate the modulatory effects of adenosine on project ion neurons in the lateral rat amygdala (LB), maintained as slices in vitro . 2 Adenosine reversibly reduced the amplitude of a fast inhibitory postsynap tic potential (IPSP) that was evoked by electrical stimulation of the exter nal capsule and pharmacologically isolated by applying an N-methyl-D-aspart ate and non-N-methyl-D-aspartate receptor antagonist, DL-(-)-2-amino-5-meth yl-4-isoxazolepropionic acid and 6,7-Dinitroquinoxaline-2,3-dione, respecti vely, and the gamma-aminobutyric acid(B) (GABA(B)) receptor antagonist CGP 35348. The postsynaptic potential that remained was abolished by locally ap plying bicuculline. 3 Adenosine reduced the amplitude of the fast IPSP on average by 40.3%. It had no significant effect on responses to exogenously applied GABA, on memb rane potential or on input resistance, suggesting that the site of action w as at presynaptic inhibitory interneurons in the LA. 4 The response to adenosine was mimicked by the selective adenosine A(1) re ceptor agonist N-6-cyclohexyladenosine and blocked by the selective adenosi ne A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine. 5 Neuronal responsiveness in the amygdala is largely controlled by inhibito ry processes. Adenosine can presynaptically downregulate inhibitory postsyn aptic responses and could exert dampening effects likely by depression elf both excitatory and inhibitory neurotransmitter release.