Cyclophosphamide-induced bladder inflammation sensitizes and enhances P2X receptor function in rat bladder sensory neurons.
We studied sensitization of retrogradely labeled bladder sensory neurons and plasticity of P2X receptor function in a model of cystitis using patch-clamp techniques. Saline (control) or cyclophosphamide (CYP) was given intraperitoneally to rats on days 0, 2, and 4. On day 5, lumbosacral (LS, L6-S2) or thoracolumbar (TL, T12-L2) dorsal root ganglia were removed and dissociated. Bladders from CYP-treated rats showed partial loss of the urothelium and greater myeloperoxidase activity compared with controls. Bladder neurons from CYP-treated rats were increased in size (based on whole cell capacitance) compared with controls and exhibited lower activation threshold, increased action potential width, and greater number of action potentials in response to current injection or application of purinergic agonists. Most control LS bladder neurons (>85%) responded to ATP or alpha,beta-metATP with a slowly desensitizing current; these agonists affected only half of TL neurons, producing predominantly fast/mixed desensitizing currents. CYP treatment increased the fraction of TL bladder neurons sensitive to purinergic agonists (>80%) and significantly increased current density in both LS and TL bladder neurons compared with control. Importantly, LS and TL neurons from CYP-treated rats showed a selective increase in the functional expression of heteromeric P2X(2/3) and homomeric P2X(3) receptors, respectively. Although desensitizing kinetics were slower in LS neurons from CYP-treated compared with control rats, recovery kinetics were similar. The present results demonstrate that bladder inflammation sensitizes and increases P2X receptor expression and/or function for both pelvic and lumbar splanchnic pathways, which contribute, in part, to the hypersensitivity associated with cystitis.
Dang
Khoa
K
Departments of Pharmacology, Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA.
Lamb
Kenneth
K
Cohen
Michael
M
Bielefeldt
Klaus
K
Gebhart
G F
GF
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002232:Carbocyanines; D048429:Cell Size; D003520:Cyclophosphamide; D018856:Cystitis, Interstitial / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007001:Hypogastric Plexus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D018836:Inflammation Mediators; D008297:Male; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011687:Purines / Q000819:agonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D013153:Splanchnic Nerves / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D001743:Urinary Bladder / Q000294:innervation / Q000378:metabolism / Q000503:physiopathology*; D019459:Urothelium / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D017833:Visceral Afferents / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology
C035005:3,3'-dihexadecylindocarbocyanine; D002232:Carbocyanines; D018836:Inflammation Mediators; C546403:P2rx2 protein, rat; C546410:P2rx3 protein, rat; D011687:Purines; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058476:Receptors, Purinergic P2X2; D058477:Receptors, Purinergic P2X3; D000255:Adenosine Triphosphate; D003520:Cyclophosphamide