GABAA and GABAB receptors modulate the K(+)-evoked release of sensory CGRP from the guinea pig urinary bladder.
Superfusion of mucosa-free muscle slices of guinea-pig urinary bladder with 40 mM K+ produced a remarkable increase in calcitonin gene-related peptide-like immunoreactivity (CGRP-LI), that in this organ is entirely contained in capsaicin-sensitive nerves. GABA (1 mM) did neither affect the basal nor the 40 mM K+ evoked CGRP-LI release. Baclofen (0.1 mM) or muscimol (1 mM) did not affect the basal CGRP-LI outflow. However, baclofen (0.1 mM) significantly reduced by 32% and muscimol (0.1-1 mM) significantly increased by 60% and 70%, respectively the K(+)-evoked CGRP-LI release. These findings add neurochemical evidence to the functional data suggesting the existence of GABAA and GABAB receptors which modulate the efferent function of capsaicin-sensitive afferents.
Santicioli
P
P
Department of Pharmacology, A. Menarini Pharmaceuticals, Florence, Italy.
Tramontana
M
M
Del Bianco
E
E
Maggi
C A
CA
Geppetti
P
P
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D011963:Receptors, GABA-A / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology*
D011963:Receptors, GABA-A; D009118:Muscimol; D001418:Baclofen; D015740:Calcitonin Gene-Related Peptide; D011188:Potassium