Action of clonidine on micturitional reflexes in decerebrate cats

Characterization of a spinal, urine storage reflex, inhibitory center and its regulation by 5-HT1A receptors in female cats

Urine storage is facilitated by somatic (pudendal nerve) and sympathetic [hypogastric nerve (HgN)] reflexes to the urethral rhabdosphincter (URS) and urethral smooth muscle, respectively, initiated by primary afferent fibers in the pelvic nerve (PelN). Inhibition of storage reflexes is required for normal voiding. This study characterizes a urine storage reflex inhibitory network that can be activated by PelN afferent fibers concurrently with the reflexes themselves. Electrical stimulation of PelN produced evoked potentials recorded by URS EMG electrodes (10-ms latency) or HgN electrodes (60-ms latency) in chloralose-anesthetized cats. When a second (i.e., paired) pulse of the same stimulus intensity was applied to the PelN 50-500 ms after the first, the reflexes evoked by the second stimulus were inhibited. The inhibition was maximal at paired-pulse intervals of 50-100 ms and remained after acute spinal transection at T10, confirming that the inhibitory center is located in the spinal cord. The 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tertralin (8-OH-DPAT; 3-300 mug/kg iv) consistently reduced the paired-pulse inhibition from 20% to 60% of control in spinal-intact animals but had no effect in acute spinal animals (i.e., supraspinal site of action). N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-2-pyridinylcyclohexanecarboxamide maleate (300 mug/kg iv) completely reversed 8-OH-DPAT's effects. The PelN-HgN reflex paired-pulse inhibition was not affected by 8-OH-DPAT. These results indicate the presence of a spinal, urine storage reflex, inhibitory center (SUSRIC) that is activated within 50 ms after activation of the reflexes themselves. SUSRIC is inhibited (disfacilitated) by supraspinal 5-HT(1A) receptors.

Chapitre C-1 B - Traitement pharmacologique de l’hyperactivité détrusorienne neurologique : drogues intrathécales

Intrathecal clonidine has been tested in spinal cord injury patients not supporting or resistant to anticholinergic drugs. Although the acute effect of clonidine on urodynamic parameters was satisfactory, cardiovascular adverse effects limited the long-term efficacy of this treatment. Intrathecal baclofen has a limited effect on overactive bladder in patients with spinal spasticity, but can modify the quality of erections and induce an incapacity to trigger ejaculation by vibratory penile stimulation.

Intrathecal clonidine for refractory detrusor hyperreflexia in spinal cord injured patients: a preliminary report

PURPOSE

We assessed the urodynamic effect of various doses of intrathecal clonidine on refractory detrusor hyperreflexia in spinal cord injured patients.

MATERIALS AND METHODS

Doses of 15, 30 or 45 microg. intrathecal clonidine or placebo were given to 5 chronic complete spinal cord injured patients with detrusor hyperreflexia. Two cystometries were performed before and 5, 30, 60, 90, 120 and 180 minutes after each injection.

RESULTS

A statistically significant dose dependent decrease in detrusor hyperreflexia was observed in each patient without significant side effect.

CONCLUSIONS

Intrathecal clonidine may represent a conservative reversible treatment for detrusor hyperreflexia via a subcutaneous programmable pump, like that used for baclofen, for spasticity. The long-term efficacy needs to be evaluated.

A comparison of clonidine, cyproheptadine and baclofen in spastic spinal cord injured patients

In twenty-five SCI subjects, antispasticity effects of three putative antispasticity agents [clonidine (an alpha-2 noradrenergic agonist), cyproheptadine (a 5-HT2 antagonist) and baclofen (a GABA-B agonist)] were tested in terms of changes in leg tone as graded by the Ashworth scale (AS), in terms of the vibratory inhibition of the H-reflex (VII) and in terms of the ability of the knee to swing passively in the pendulum test as quantified by video motion analysis. When compared to the no drug period, all three drug treatments showed an antispasticity effect on the AS, the VII and the amplitude of the first swing and the relaxation index of the pendulum test, p. < 0001. Surprisingly, cyproheptadine and baclofen produced a greater reduction in the VII than clonidine, p. < 01. The amplitude of the first swing in the pendulum test correlated well with the AS, r = .88, and the antispasticity effects of the drugs produced improvements in both measures, a reduced AS and increased amplitude of knee swing in the pendulum test. Therefore, video motion analysis of the pendulum test is as valid a measure of spasticity as the Ashworth scale and is not limited by subjectivity of the examiner.

Treatment of mammalian spinal cord injury with antioxidants

After spinal cord injury, two groups of cats were treated with a combination of methylprednisolone sodium succinate (MP, 35 mg/kg) and epsilon-aminocaproic acid (EACA, 350 mg/kg), and guanabenz acetate (0.65 mg/kg). Guanabenz acetate was administered twice daily for 8 weeks. In the first group, the treatment significantly increased blood flow in the abdominal aorta. All cats treated with guanabenz acetate 3 hr after spinal cord contusion had return of micturition and none suffered complete paraplegia. Four animals had partial and the other four had complete motor recovery. A superoxide (O2-.) generating system, horseradish peroxidase, decreased [14C]gamma amino butyric acid uptake by mouse cortical slices by 33% but when superoxide dismutase was added to the medium, the uptake was reduced by only 9%. The nerve endings were also protected by superoxide dismutase from morphologic damage by O2-. as observed by electron microscopy. The agents used in these studies produce their ameliorating effects by virtue of their anti-inflammatory, antioxidant, and membrane stabilizing properties, and enhancing the regional microcirculation. In addition to having these properties, guanabenz acetate is also an alpha 2 adrenoceptor agonist.