RESUMO
The cornea is extensively innervated by trigeminal ganglion cold thermoreceptor neurons expressing TRPM8 (transient receptor potential cation channel subfamily M member 8). These neurons respond to cooling, hyperosmolarity and wetness of the corneal surface. Surgical injury of corneal nerve fibers alters tear production and often causes dry eye sensation. The contribution of TRPM8-expressing corneal cold-sensitive neurons (CCSNs) to these symptoms is unclear. Using extracellular recording of CCSNs nerve terminals combined with in vivo confocal tracking of reinnervation, Ca2+ imaging and patch-clamp recordings of fluorescent retrogradely labeled corneal neurons in culture, we analyzed the functional modifications of CCSNs induced by peripheral axonal damage in male mice. After injury, the percentage of CCSNs, the cold- and menthol-evoked intracellular [Ca2+] rises and the TRPM8 current density in CCSNs were larger than in sham animals, with no differences in the brake K+ current IKD Active and passive membrane properties of CCSNs from both groups were alike and corresponded mainly to those of canonical low- and high-threshold cold thermoreceptor neurons. Ongoing firing activity and menthol sensitivity were higher in CCSN terminals of injured mice, an observation accounted for by mathematical modeling. These functional changes developed in parallel with a partial reinnervation of the cornea by TRPM8(+) fibers and with an increase in basal tearing in injured animals compared with sham mice. Our results unveil key TRPM8-dependent functional changes in CCSNs in response to injury, suggesting that increased tearing rate and ocular dryness sensation derived from deep surgical ablation of corneal nerves are due to enhanced functional expression of TRPM8 channels in these injured trigeminal primary sensory neurons.SIGNIFICANCE STATEMENT We unveil a key role of TRPM8 channels in the sensory and autonomic disturbances associated with surgical damage of eye surface nerves. We studied the damage-induced functional alterations of corneal cold-sensitive neurons using confocal tracking of reinnervation, extracellular corneal nerve terminal recordings, tearing measurements in vivo, Ca2+ imaging and patch-clamp recordings of cultured corneal neurons, and mathematical modeling. Corneal nerve ablation upregulates TRPM8 mainly in canonical cold thermoreceptors, enhancing their cold and menthol sensitivity, inducing a rise in the ongoing firing activity of TRPM8(+) nerve endings and an increase in basal tearing. Our results suggest that unpleasant dryness sensations, together with augmented tearing rate after corneal nerve injury, are largely due to upregulation of TRPM8 in cold thermoreceptor neurons.
Assuntos
Axônios/fisiologia , Temperatura Baixa , Córnea/inervação , Córnea/fisiologia , Células Receptoras Sensoriais/fisiologia , Canais de Cátion TRPM/fisiologia , Sensação Térmica/fisiologia , Animais , Lesões da Córnea/fisiopatologia , Fenômenos Eletrofisiológicos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Modelos Neurológicos , Modelos Teóricos , Fibras Nervosas , Técnicas de Patch-Clamp , Lágrimas , Termorreceptores/fisiologiaRESUMO
Mammalian peripheral cold thermoreceptors respond to cooling of their sensory endings with an increase in firing rate and modification of their discharge pattern. We recently showed that cultured trigeminal cold-sensitive (CS) neurons express a prominent hyperpolarization-activated current (I(h)), mainly carried by HCN1 channels, supporting subthreshold resonance in the soma without participating in the response to acute cooling. However, peripheral pharmacological blockade of I(h), or characterization of HCN1(-/-) mice, reveals a deficit in acute cold detection. Here we investigated the role of I(h) in CS nerve endings, where cold sensory transduction actually takes place. Corneal CS nerve endings in mice show a rhythmic spiking activity at neutral skin temperature that switches to bursting mode when the temperature is lowered. I(h) blockers ZD7288 and ivabradine alter firing patterns of CS nerve endings, lengthening interspike intervals and inducing bursts at neutral skin temperature. We characterized the CS nerve endings from HCN1(-/-) mouse corneas and found that they behave similar to wild type, although with a lower slope in the firing frequency vs. temperature relationship, thus explaining the deficit in cold perception of HCN1(-/-) mice. The firing pattern of nerve endings from HCN1(-/-) mice was also affected by ZD7288, which we attribute to the presence of HCN2 channels in the place of HCN1. Mathematical modeling shows that the firing phenotype of CS nerve endings from HCN1(-/-) mice can be reproduced by replacing HCN1 channels with the slower HCN2 channels rather than by abolishing I(h). We propose that I(h) carried by HCN1 channels helps tune the frequency of the oscillation and the length of bursts underlying regular spiking in cold thermoreceptors, having important implications for neural coding of cold sensation.
Assuntos
Potenciais de Ação/fisiologia , Canais de Cátion Regulados por Nucleotídeos Cíclicos/genética , Terminações Nervosas/fisiologia , Canais de Potássio/genética , Termorreceptores/fisiologia , Potenciais de Ação/genética , Animais , Benzazepinas/farmacologia , Fármacos Cardiovasculares/farmacologia , Temperatura Baixa , Córnea/inervação , Canais de Cátion Regulados por Nucleotídeos Cíclicos/antagonistas & inibidores , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização , Canais Iônicos/antagonistas & inibidores , Canais Iônicos/metabolismo , Ivabradina , Camundongos , Modelos Neurológicos , Nervo Óptico/fisiologia , Pirimidinas/farmacologiaRESUMO
PURPOSE: This study evaluated the long-term (5-year) durability of radiofrequency energy delivery for fecal incontinence. METHODS: This was an extension of the follow-up from our original prospective study in which patients who suffered from fecal incontinence were treated with the SECCA system for radiofrequency energy delivery to the anal canal muscle. The Cleveland Clinic Florida Fecal Incontinence Scale (0-20), fecal incontinence-related quality of life score, and Medical Outcomes Study Short-Form 36 were administered to five years. Differences between baseline and follow-up were analyzed by using paired t-test. RESULTS: A total of 19 patients were treated and followed for five years, including 18 females (aged 57.1 (range, 44-77) years). The mean duration for fecal incontinence was 7.1 (range, 1-21) years. At five-year follow-up, the mean fecal incontinence score had improved from 14.37 to 8.26 (P<0.00025) with 16 patients (84.2 percent) demonstrating>50 percent improvement. All fecal incontinence-related quality of life scores improved, including lifestyle (2.43 to 3.15; P<0.00075), coping (1.73 to 2.6; P<0.00083), depression (2.24 to 3.15; P<0.0002), and embarrassment (1.56 to 2.51; P<0.0003). The social function component of the Short-Form 36 improved from 38.3 to 60 (P<0.05). There was a trend toward improvement in the mental component summary of the Short-Form 36 from 38.1 to 48.14. There were no long-term complications. CONCLUSIONS: Significant and sustained improvements in fecal incontinence symptoms and quality of life are seen at five years after treatment with the SECCA system. This treatment should be considered for patients suffering from fecal incontinence not amenable to surgery and who have failed conservative management.
Assuntos
Diatermia/métodos , Incontinência Fecal/cirurgia , Adulto , Idoso , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias , Estatísticas não Paramétricas , Resultado do TratamentoRESUMO
PURPOSE: This study evaluated the durability and long-term safety of radio-frequency energy delivery for fecal incontinence (Secca procedure). METHODS: This was an extended follow-up of a prospective study in which patients with fecal incontinence of various causes underwent radio-frequency energy delivery to the anal canal muscle. The Cleveland Clinic Florida Fecal Incontinence Scale (0-20), fecal incontinence-related quality-of-life score, and Medical Outcomes Study Short Form 36 were administered at baseline and at 1, 2, 3, 6, 12, and 24 months after the procedure. Differences between baseline and follow-up were analyzed with the Wilcoxon signed-rank test. RESULTS: Ten females (aged 55.9 +/- 9.2 (range, 44-74) years) were treated. At two-year follow-up, the mean Cleveland Clinic Florida Fecal Incontinence Scale score was improved from 13.8 to 7.3 (P = 0.002), with eight patients having scores of < or =10. All fecal incontinence-related quality-of-life score parameters were improved, including lifestyle (from 2.3 to 3.3; P = 0.002), coping (from 1.7 to 2.7; P = 0.002), depression (from 2.4 to 3.4; P = 0.004), and embarrassment (from 1.5 to 2.4; P = 0.008). There was no decrement in effect noted in any parameter between 12 and 24 months (P > 0.2). The social function component of the Short Form 36 improved from 50 to 82.5 (P = 0.04), whereas there was an improvement trend for the mental component summary of the Short Form 36 from 38.3 to 48.1 (P = 0.11). Protective pad use was eliminated in four of the seven baseline users. There were no long-term complications, such as stricture, pain, or constipation. CONCLUSIONS: A significant improvement in symptoms of fecal incontinence and quality of life persists two years after radio-frequency delivery to the anal canal, which demonstrates durability of this intervention.
Assuntos
Diatermia , Incontinência Fecal/terapia , Adulto , Idoso , Feminino , Seguimentos , Humanos , Pessoa de Meia-Idade , Estudos Prospectivos , Qualidade de Vida , Resultado do TratamentoRESUMO
PURPOSE: In this prospective study we investigated the feasibility, safety, and efficacy of radio-frequency energy delivery deep to the mucosa of the anal canal for the treatment of fecal incontinence. METHODS: We studied ten patients with fecal incontinence of varying causes. All patients underwent anoscopy, anorectal manometry, endorectal ultrasound, and pudendal nerve terminal motor latency testing at baseline and six months. The Cleveland Clinic Florida scale for fecal incontinence (Wexner, 0-20), fecal incontinence-related quality of life score, and Short Form 36 were administered at baseline, 1, 2, 3, 6, and 12 months. Using conscious sedation and local anesthesia, we delivered temperature-controlled radio-frequency energy via an anoscopic device with multiple needle electrodes to create thermal lesions deep to the mucosa of the anal canal. RESULTS: Ten females (age, 55.9 +/- 9.2 years; range, 44-74) were enrolled and treated. Median discomfort by visual analog scale (0-10) was 3.8 during and 0.9 two hours after the procedure. Bleeding occurred in four patients (14-21 days after procedure), spontaneous resolution (n = 3) and anoscopic suture ligation (n = 1). At 12 months, the median Wexner score improved from 13.5 to 5 (P < 0.001), with 80 percent of patients considered responders. All parameters in the fecal incontinence-related quality of life were improved (lifestyle (from 2.3 to 3.4), coping (from 1.4 to 2.7), depression (from 2.2 to 3.5), and embarrassment (from 1.3 to 2.8); P < 0.05 for all parameters). Protective pad use was eliminated in five of the seven baseline users. At six months, there was a significant reduction in both initial and maximum tolerable rectal distention volumes. Anoscopy was normal at six months. CONCLUSION: Radio-frequency energy delivery to the anal canal for treatment of fecal incontinence is a new modality that, in this study group, safely improved Wexner and fecal incontinence-related quality of life scores, eliminated protective pad use in most patients, and improved patient quality of life.