Adenosine reduces GABAergic IPSC frequency via presynaptic A1 receptors in hypothalamic paraventricular neurons projecting to rostral ventrolateral medulla

Tae Hee Han,Soo Hwa Jang,So Yeong Lee,Pan Dong Ryu. Neuroscience Letters

Volume 490, Issue 1, 18 February 2011, Pages 63–67. doi:10.1016/j.neulet.2010. 12.026. The paraventricular nucleus (PVN) is a brain region that has projections that go to RVLM and down to the IML in order to modulate sympathetic outflow. The purpose of this study was to determine whether adenosine was was playing a role in modulating gaba release from PVN-RVLM neurons. Using young male Sprague-Dawley they labelled PVN-RVLM neurons by injecting Fluospheres- Red into the RVLM and they allowed the animal to recover for 5-7 days. the brain was sectioned and the labelled PVN neurons were selected for recording. In response to adenosine, they saw inhibitory postsynaptic currents . When compared to the before activity there was a decrease in firing but not in amplitude and the response was concentration dependent. Then they used antagonist to A 1 receptor and the A2  receptor  and saw that there was no change in the firing of the neuron. however, when adenosine was given  after the  microinjection of the A1 antagonist they found that the iPSCs was inhibited.  the microinjection of  the A2 antagonist  did not prevent the IPSCs that occur in response to  adenosine injection. These data demonstrate that adenosine is playing a  role presynaptically  in attenuating GABA release and this mediated by adenosine acting on A1 receptors. -MD