Abstract
Acetylcholine released from parasympathetic excitatory nerves activates
contraction in detrusor smooth muscle. Immunohistochemical labeling of
guinea pig detrusor with anti-c-Kit and anti-VAChT demonstrated a close
structural relationship between interstitial cells of Cajal (ICC) and cholinergic
nerves. The ability of guinea pig bladder detrusor ICC to respond
to the acetylcholine analog, carbachol, was investigated in enzymatically
dissociated cells, loaded with the Ca2+ indicator fluo 4AM. ICC fired
Ca2+ transients in response to stimulation by carbachol (1/10 M). Their
pharmacology was consistent with carbachol-induced contractions in
strips of detrusor which were inhibited by 4-DAMP (1 M), an M3
receptor antagonist, but not by the M2 receptor antagonist methoctramine
(1 M). The source of Ca2+ underlying the carbachol transients in
isolated ICC was investigated using agents to interfere with influx or
release from intracellular stores. Nifedipine (1 M) or Ni2 (30-100
M) to block Ca2+ channels or the removal of external Ca2 reduced the
amplitude of the carbachol transients. Application of ryanodine (30 M)
or tetracaine (100 M) abolished the transients. The phospholipase C
inhibitor, U-73122 (2.5 M), significantly reduced the responses. 2-Aminoethoxydiethylborate
(30 M) caused a significant reduction and Xestospongin
C (1 M) was more effective, almost abolishing the responses.
Intact in situ preparations of guinea pig bladder loaded with a Ca2+ indicator showed distinctively different patterns of spontaneous Ca2+ events in smooth muscle cells and ICC. Both cell types responded to
carbachol by an increase in frequency of these events. In conclusion, guinea pig bladder detrusor ICC, both as isolated cells and within whole tissue preparations, respond to cholinergic stimulation by firing Ca2+ transients.
Original language | English |
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Pages (from-to) | F645-F655 |
Number of pages | 11 |
Journal | American Journal of Physiology - Renal Physiology |
Volume | 294 |
Issue number | 3 |
DOIs | |
Publication status | Published - Mar 2008 |
Keywords
- confocal microscopy
- c-Kit