Cyclophosphamide cystitis as a model of visceral pain in rats: model elaboration and spinal structures involved as revealed by the expression of c-Fos and Krox-24 proteins

Abstract

The evoked expression of the immediate early gene (IEG)-encoded proteins c-Fos and Krox-24 was used to monitor spinal visceronociceptive processing that results from cyclophosphamide cystitis in behaving rats. Animals received a single dose of 100 mg/kg i.p. of cyclophosphamide and survived for 30 min to 5 h. Longer survival times were not considered because of ethical considerations. Cyclophosphamide-injected animals developed characteristic behavioral signs in parallel with development of bladder lesions and spinal evoked expression of IEG-encoded proteins. Histological examination of the urinary bladder was used to evaluate the degree of cystitis and as a criterion for selection of groups of animals to be quantitatively analyzed. Controls consisted of freely behaving animals including control (un-injected), sham (saline-injected) or diuretic (furosemide-injected) animals. Behavioral modifications consisted of lacrimation, piloerection, assumption of a peculiar "rounded-back" posture, which was accompanied by head immobility and various brief "crises" (tail hyperextension, abdominal retractions, licking of the lower abdomen, backward withdrawal movements). Abnormal behaviors, which first appeared (lacrimation, piloerection) at the end of postinjection hour 1, progressively increased in severity (rounded-back posture) over the following 90 min to reach a plateau at about postinjection hour 2; the rounded-back posture was maintained up to time of death. Histological modifications of bladder tissue were assessed using a 4-grade scale in a blind setting. The 1st grade consisted of control or sham animals with no bladder lesion; 2nd grade, animals with simple chorionic edema; 3rd grade, animals with chorionic edema associated with mucosal abrasion, fibrin deposit, and onset of polymorphonuclear leukocyte infiltration; 4th grade, animals with complete cystitis corresponding to an increase in severity and spread of all the signs of cystitis described above plus petechial hemorrhage. Simple chorionic edema was observed from 30 min to 3 h postinjection, but with a progressive increase in severity over time. Edema accompanied by epithelial abrasion was observed for animals that survived 3-4 h postinjection; complete inflammation was observed in animals that survived 4-5 h postinjection. The study of c-Fos- and Krox-24-encoded protein expression demonstrated that few lumbosacral spinal areas were specifically involved in the processing of visceral inputs in response to bladder stimulation. These areas were the parasympathetic column (SPN), the dorsal gray commissure (DGC as the caudal extent of lamina X), and superficial layers of the dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of corticotropin-releasing factor and CRF receptors in micturition pathways after cyclophosphamide-induced cystitis

“…In contrast, increases in PGD 2 in the urinary bladder were biphasic, occurring with both acute (4 h) and chronic CYP treatment but not acute (48 h) treatment (14). Animal studies have also indicated that CYP treatment (acute treatment) in the rat induces increased frequency of voiding in awake rats and urinary bladder hyperreflexia in anesthetized rats (14,(21)(22)(23)26), and these changes are maintained with acute (48 h) and chronic CYP treatment. Thus CYP treatment represents a noxious, chemical irritation of the urinary bladder that also induces bladder overactivity.…”

Cyclophosphamide-Induced Bladder Inflammation Sensitizes and Enhances P2X Receptor Function in Rat Bladder Sensory Neurons

“…In the present report, we used a well-established model of urinary bladder inflammation (Bon et al 1997(Bon et al , 2003Lanteri-Minet et al 1995) to examine the consequences of inflammation on characteristics of TL and LS bladder neurons in the rat, focusing on their sensitivity to purinergic receptor agonists. We hypothesized that changes in the excitability and sensitivity of bladder sensory neurons to endogenous purinergic receptor agonists contribute to bladder dysfunction, discomfort, and pain that characterize bladder disorders such as cystitis.…”

Expression of Phosphorylated cAMP Response Element Binding Protein (p-CREB) in Bladder Afferent Pathways in VIP−/− Mice with Cyclophosphamide (CYP)-Induced Cystitis

“…Numerous studies involving a chemically (cyclophosphamide; CYP)-induced bladder inflammation (Cox, 1979;Maggi et al, 1992;Lantéri-Minet et al, 1995;Vizzard, 2000a;Vizzard, 2000d;Zvarova and Vizzard, 2006) model have demonstrated alterations in neurochemical (Vizzard, 2000a;Vizzard, 2000dVizzard, , 2001Zvarova and Vizzard, 2006), electrophysiological (Jennings and Vizzard, 1999;Yoshimura and de Groat, 1999), organizational (Vizzard and Boyle, 1999;Vizzard, 2000b) and functional properties of bladder afferent neurons in dorsal root ganglia (DRG) and in central reflex micturition pathways as well as changes in the urinary bladder (xx). Neurotrophins, including nerve growth factor (NGF) have been implicated in mediating some of these changes.…”