Data from: GCaMP6f-expressing chromaffin cells in murine adrenal slices exhibit dynamic spontaneous calcium responses that do not require nerve input

Chromaffin cells of the adrenal medulla exhibit spontaneous action
potentials and intracellular Ca2+ responses that, when dissociated in
vitro, result in catecholamine secretion. However, spontaneous activity in
these cells is nearly abolished when splanchnic nerve input is blocked in
vivo. To address this discrepancy, we examined spontaneous Ca2+ responses
in chromaffin cells using an intermediate preparation: adrenal slices from
transgenic mice expressing the genetically encoded Ca2+ indicator GCaMP6f
selectively in these cells. Within this preparation, the three-dimensional
structure and extracellular environment surrounding chromaffin cells are
retained, as is input from distal splanchnic nerve terminals, which
spontaneously release the neurotransmitter acetylcholine. Chromaffin cells
within these slices displayed spontaneous Ca2+ responses with frequencies
and amplitudes that varied greatly within and between individual cells.
However, population averages remained stable, providing a tool to measure
the cellular and molecular mechanisms underlying these responses. While
overall average frequencies and amplitudes of spontaneous Ca2+ responses
depended on the influx of extracellular Ca2+ through voltage-gated Ca2+
channels, they did not require Ca2+ release from intracellular stores,
splanchnic nerve input, or activation of voltage-gated sodium channels.
Together, these results suggest that spontaneous activity in chromaffin
cells in adrenal slices is generated autonomously, similar to that in
dissociated chromaffin cells. By contrast, spontaneous activity in
chromaffin cells in intact animals likely represents a distinct form that
depends on basal input from the intact splanchnic nerve. This study
provides a foundation to further explore the diverse mechanisms mediating
chromaffin cell activation.