Abstract
Our previous studies suggested that mitochondria supplied ATP for activation of nonselective cation (NS) channels in response to muscarinic receptor (mAChR) stimulation in guinea-pig adrenal chromaffin cells. Thus, we investigated with fluorescent techniques which part of the cell membrane contained mAChRs and NS channels in guinea-pig chromaffin cells and whether mitochondria were present near the receptor and channel. The m4AChR was detected in the adrenal medulla and not in the cortex with the immunohistochemical technique and immunoblotting, whereas the m3AChR was not in either the adrenal medulla or the cortex. This result taken together with previous findings indicates that m4AChR is functionally associated with a NS channel in chromaffin cells. The confocal microscopic study revealed that the m4-like immunoreactivity was mainly distributed in the membrane area near the nucleus. The intracellular concentration of Na+, as measured with SBFI dye, increased in response to muscarine, and this increase was larger in the nuclear portion than in the non-nulcear portion. Mitochondria, as visualized with rhodamine 123, were also localized underneath the plasma membrane in the nuclear portion. The results indicate that the m4AChR and probably NS channels are distributed in the plasma membrane near the nucleus and mitochondria may be present underneath such a membrane. [Jpn J Physiol 55 Suppl:S132 (2005)]
