Biochemical, anatomical and functional correlates of postnatal development of the capsaicin-sensitive innervation of the rat urinary bladder.
The postnatal development of substance P-like immunoreactivity (SP-LI) in the urinary bladder (assayed by radioimmunoassay and immunohistochemistry) was investigated in rats and compared with changes in the contractile response to acetylcholine, SP or capsaicin. In adult rats, bladder SP-LI was depleted by systemic capsaicin desensitization or extrinsic bladder denervation indicating that it is completely stored in sensory nerves. Bladder SP-LI was not detected in rat fetuses nor in newborn rats until day 3 of postnatal life (P3). SP-LI increased thereafter to reach, at P20, values approaching 60% of the SP-LI observed in the adult rat. By immunohistochemistry, SP-LI positive varicose fibers were not observed until P13. The contractile response to capsaicin was absent at P0, both in vivo (topical application) and in vitro. In adult rats, the capsaicin-induced bladder contraction was abolished by extrinsic denervation and is produced by release of transmitters from sensory nerves. The amplitude of the capsaicin-induced contraction in the postnatal rat bladder was significantly correlated with SP-LI concentration in the organ. Bladders excised from newborn (P0) or adult rats were equally sensitive to exogenous SP which, in both cases, produced a concentration-related contraction. It is concluded that the postnatal development of the 'efferent' function mediated by capsaicin-sensitive nerves of the rat bladder is strictly related to development of peptidergic sensory innervation.
Maggi
C A
CA
Pharmacology Department, Research Laboratories, A. Menarini Pharmaceuticals, Florence, Italy.
Santicioli
P
P
Geppetti
P
P
Frilli
S
S
Spillantini
M G
MG
Nediani
C
C
Hunt
S P
SP
Meli
A
A
D000109:Acetylcholine / Q000494:pharmacology; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000378:metabolism* / Q000494:pharmacology / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects / Q000254:growth & development / Q000294:innervation*
D013373:Substance P; D000109:Acetylcholine; D002211:Capsaicin