Fig. 3.

Purinergic and cholinergic signaling differentially regulate ascending and descending divisions of the myenteric circuitry. (A, Left) Under baseline conditions, descending FTS provokes an increase in neuronal Ca²⁺ levels that is largely unaffected by the purinergic blocker MRS2179 but is augmented by the M3 cholinergic blocker J104129. (Right) J104129 does not affect the magnitude of the neuronal response evoked by ascending FTS, whereas MRS2179 reduces this response by nearly 40% compared with controls (black versus white bars). (B, Left) Glial Ca²⁺ responses triggered by descending FTS are reduced by MRS2179 and augmented by J104129. (Right) Glial recruitment consequent to ascending FTS is attenuated by MRS2179 and augmented by J104129. All values represent means ± SEM. (C) In the presence of MRS2179, ∼15% of all responsive neurons were activated exclusively by descending FTS, while only 4% of glia were recruited by the same stimulus. In contrast, 19% of neurons were activated exclusively by ascending FTS, while 21% of glia were recruited by ascending FTS in the presence of MRS2179. (D) In the presence of J104129, 3% of neurons were activated by descending FTS, while 4% of glia were recruited by the same stimulus. Ascending FTS activated 11% of neurons within a myenteric ganglion in the presence of J104129, while 1% of glia were recruited under this condition. (E and F) Summary table comparing proportions of neurons that are activated (E) and glia that are activated and recruited (F) by directional FTS in the presence of MRS2179 or J104129. (G) Summary diagram recapitulating how cholinergic or purinergic blockade alters neuronal and glial population recruitment dynamics within each circuit pathway. MRS2179 reduces neuronal recruitment by ascending pathways, which expands the pool of neurons associated with the descending circuitry (white → blue circles). J104129 bolsters neuron recruitment within the descending pathway, expanding the pool of neurons functionally affiliated with both pathways (orange → white circles). n.s., not significant. ****P < 0.0001.