Stimulation of bladder activity by volume, L-dopa and capsaicin in normal conscious rats--effects of spinal alpha 1-adrenoceptor blockade.

Article Details

Citation

Copy to clipboard

Ishizuka O, Pandita RK, Mattiasson A, Steers WD, Andersson KE

Stimulation of bladder activity by volume, L-dopa and capsaicin in normal conscious rats--effects of spinal alpha 1-adrenoceptor blockade.

Naunyn Schmiedebergs Arch Pharmacol. 1997 Jun;355(6):787-93.

PubMed ID

9205965 [ View in PubMed

]

Abstract

To study possible differences in alpha 1-adrenoceptor involvement in the spinal mechanisms mediating bladder activity induced by volume (bladder filling), central (L-dopa), and peripheral (capsaicin) stimulation, we investigated if these types of bladder activity were modified by intrathecal (i.t.) or intra-arterial (i.a.) administration of the alpha 1-adrenoceptor antagonist, indoramin. Indoramin is selective for the alpha 1A-adrenoceptor subtype, whereas most clinically used alpha 1-adrenoceptor antagonists, including doxazosin, have no subtype selectivity. The drug effects were studied by continuous cystometry in normal, conscious rats and rats with bladder activity evoked by intraperitoneal L-dopa (50 mg/kg after carbidopa pretreatment), or by intravesical capsaicin (30 microM). I.t. indoramin (50 nmol) significantly decreased micturition pressure, and increased bladder capacity and micturition volume. Dribbling incontinence due to urinary retention was observed in one of ten rats. L-dopa-stimulated bladder overactivity was significantly attenuated by i.t. or i.a. indoramin (50 nmol). Similar effects of i.t. and i.a. doxazosin (50 nmol) have been reported previously. Intravesical capsaicin (30 microM) caused bladder activity, which was attenuated by i.t. indoramin (50 nmol), but not by i.t. doxazosin (50 nmol). I.a. indoramin did not reduce capsaicin-induced bladder activity; doxazosin was moderately effective. The results suggest that the bulbospinal micturition reflex evoked by bladder filling and L-dopa involves a descending pathway where transmission is partly mediated by spinal alpha 1-adrenoceptors. Bladder overactivity evoked by intravesical capsaicin, which elicits a vesicospinal-vesical reflex, was not affected by i.t. doxazosin in a dose that attenuates activity mediated through the bulbo-spinal pathway. This suggests less involvement of spinal alpha 1-adrenoceptors in the vesico-spinal-vesical than in the bulbo-spinal voiding reflex.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Doxazosin	Alpha-1A adrenergic receptor	Protein	Humans	Yes	Antagonist	Details