Neuromuscular transmission and innervation in the urinary bladder of the insectivore Suncus murinus

Abstract

In isolated preparations of the urinary bladder detrusor of the house musk shrew Suncus murinus (order: insectivora; family: Soricidae), electrical field stimulation (0.5–32 pulses/s) evoked neurogenic contractile responses that were markedly attenuated by atropine (1 μM). The non-cholinergic component was reduced but not abolished by the P 2-purinoceptor antagonist, suramin (300 μM). Thus, neuromuscular transmission in the suncus urinary bladder is effected by cholinergic and purinergic nerves together with an as-yet unidentified component. Using immunohistochemical methods, the suncus urinary bladder was seen to be supplied by nerves containing neuropeptide Y, tyrosine hydroxylase, vasoactive intestinal polypeptide, galanin, substance P, calcitonin gene-related peptide and type I nitric oxide synthase. The pattern of responses to electrical field stimulation was more similar to that of humans and Old World primates, than to that of rodents or lagomorphs. The pattern of innervation of the bladder wall, in terms of the distribution of populations containing a given neuropeptide, was very similar to that in humans. Hence, Suncus murinus may provide a novel species for modelling the neuropharmacology of the human bladder, and also for studying the evolution of autonomic innervation.