Ca(V)3.2 channels and the induction of negative feedback in cerebral arteries.

RATIONALE: T-type (CaV3.1/CaV3.2) Ca(2+) channels are expressed in rat cerebral arterial smooth muscle. Although present, their functional significance remains uncertain with findings pointing to a variety of roles. OBJECTIVE: This study tested whether CaV3.2 channels mediate a negative feedback response by triggering Ca(2+) sparks, discrete events that initiate arterial hyperpolarization by activating large-conductance Ca(2+)-activated K(+) channels. METHODS AND RESULTS: Micromolar Ni(2+), an agent that selectively blocks CaV3.2 but not CaV1.2/CaV3.1, was first shown to depolarize/constrict pressurized rat cerebral arteries; no effect was observed in CaV3.2(-/-) arteries. Structural analysis using 3-dimensional tomography, immunolabeling, and a proximity ligation assay next revealed the existence of microdomains in cerebral arterial smooth muscle which comprised sarcoplasmic reticulum and caveolae. Within these discrete structures, CaV3.2 and ryanodine receptor resided in close apposition to one another. Computational modeling revealed that Ca(2+) influx through CaV3.2 could repetitively activate ryanodine receptor, inducing discrete Ca(2+)-induced Ca(2+) release events in a voltage-dependent manner. In keeping with theoretical observations, rapid Ca(2+) imaging and perforated patch clamp electrophysiology demonstrated that Ni(2+) suppressed Ca(2+) sparks and consequently spontaneous transient outward K(+) currents, large-conductance Ca(2+)-activated K(+) channel mediated events. Additional functional work on pressurized arteries noted that paxilline, a large-conductance Ca(2+)-activated K(+) channel inhibitor, elicited arterial constriction equivalent, and not additive, to Ni(2+). Key experiments on human cerebral arteries indicate that CaV3.2 is present and drives a comparable response to moderate constriction. CONCLUSIONS: These findings indicate for the first time that CaV3.2 channels localize to discrete microdomains and drive ryanodine receptor-mediated Ca(2+) sparks, enabling large-conductance Ca(2+)-activated K(+) channel activation, hyperpolarization, and attenuation of cerebral arterial constriction.

Successful physical therapy for constipation related to puborectalis dyssynergia improves symptom severity and quality of life.

PURPOSE: This study evaluated symptom severity and quality of life in patients with puborectalis dyssynergia before and after physical therapy. METHODS: Twenty-two patients with puborectalis dyssynergia were prospectively enrolled into a multidisciplinary program for the treatment of pelvic floor and bowel disorders in this case series. All patients had functional constipation and evidence of puborectalis dyssynergia. Physical therapy and behavioral counseling were offered to all. Patients completed the Patient Health Questionnaire, the Patient-Assessment of Constipation Symptom Questionnaire, and the Patient-Assessment of Constipation Quality of Life Questionnaire. RESULTS: Sixteen patients successfully completed the program. Symptom severity decreased after physical therapy (2.1 +/- 0.7 vs. 1.3 +/- 0.9, P = 0.007). Quality of life also improved significantly (2.6 +/- 0.8 vs. 1.5 +/- 1.0, P = 0.007). Patients reported less physical discomfort, fewer worries/concerns, and indicated satisfaction with treatment. The difference in symptom severity was highly correlated with improvement in quality of life (r = 0.7, P = .005). CONCLUSIONS: Successful physical therapy for patients with puborectalis dyssynergia is associated with improvements in constipation-related symptoms and in quality of life.