Blockade of gap junctions markedly alters hypoglossal motor discharge in arterially‐perfused adult rat

Abstract

In the arterially‐perfused adult rat, pharmacological blockade of gap junctions increases frequency, decreases amplitude, and in some cases, alters the pattern of phrenic bursts. The role of functional gap junction coupling in hypoglossal (XII) motor output in this preparation, however, remains to be identified. Therefore, we examined the effects of pharmacological blockade of gap junctions using carbenoxolone (CBX; 100 μM; n=20) on phrenic and XII nerve discharges in arterially‐perfused adult rats; experiments were also conducted using the inert analog glycyrrhzic acid (GZA; 100 μM, n=6) as a control for non‐specific effects of CBX. We found that perfusion with CBX (1) increased phrenic and XII burst frequency by significantly reducing both burst duration and the duration between bursts, (2) decreased phrenic and XII burst amplitude, and (3) shifted the time‐to‐peak to an earlier time point in the phrenic and XII bursts. The effects of CBX on XII burst timing and patterning were greater that those observed for phrenic bursts, with pre‐I XII discharge being markedly reduced or absent in most, but not all, XII bursts. In contrast, GZA was ineffective in similarly altering phrenic or XII activity. These data lend further support to a role of gap junctions in central respiratory control in adult rat, and suggest that the role of gap junction coupling in phrenic and XII motor control may not be identical. Supported by NS045321