Cyclic AMP ‐producing chemogenetic activation of indirect pathway striatal projection neurons and the downstream effects on the globus pallidus and subthalamic nucleus in freely moving mice

The indirect pathway striatal medium spiny projection neurons ( iMSN s) are critical to motor and cognitive brain functions. These neurons express a high level of cAMP ‐increasing adenosine A2a receptors. However, the potential effects of cAMP production on iMSN spiking activity have not been established, and recording identified iMSN s in freely moving animals is challenging. Here, we show that in the transgenic mice expressing cAMP ‐producing G protein G s ‐coupled designer receptor exclusively activated by designer drug (Gs‐ DREADD ) in iMSN s, the baseline spike firing in MSN s is normal, indicating DREADD expression does not affect the normal physiology of these neurons. Intraperitoneal injection of the DREADD agonist clozapine‐N‐oxide ( CNO ; 2.5 mg/kg) increased the spike firing in 50% of the recorded MSN s. However, CNO did not affect MSN firing in Gs‐ DREADD ‐negative mice. We also found that CNO injection inhibited the spike firing of globus pallidus external segment ( GP e) neurons in Gs‐ DREADD ‐positive mice, further indicating CNO excitation of iMSN s. Temporally coincident with these effects on spiking firing in the indirect pathway, CNO injection selectively inhibited locomotion in D2 Gs‐ DREADD mice. Taken together, our results strongly suggest that cAMP production in iMSN s can increase iMSN spiking activity and cause motor inhibition, thus addressing a long‐standing question about the cellular functions of the cAMP ‐producing adenosine A2a receptors in iMSN s.Cover Image for this issue: doi: 10.1111/jnc.14181 .