Modulatory action of galanin on responses due to antidromic activation of peripheral terminals of capsaicin-sensitive sensory nerves.
Galanin inhibited, in a concentration-dependent manner (EC50 7.2 nM), the positive inotropic response produced by field stimulation of isolated left atria from reserpine-pretreated guinea-pigs (in the presence of atropine). These responses were shown to involve antidromic activation of capsaicin-sensitive primary afferents. On the other hand, galanin did not affect the inotropic response to capsaicin or calcitonin gene-related peptide, the putative endogenous mediator released from sensory nerves. Galanin-(1-10) was at least 10,000 times less potent than the parent peptide, while galanin-(25-29) was ineffective. Likewise, galanin inhibited the non-cholinergic contraction produced by field stimulation of the isolated guinea-pig bronchus but not the contraction produced by exogenous neurokinin A. These findings indicate a prejunctional neuromodulatory action of galanin on the excitability of peripheral terminals of capsaicin-sensitive sensory nerves.
Giuliani
S
S
Pharmacology Department, A. Menarini Pharmaceuticals, Florence, Italy.
Amann
R
R
Papini
A M
AM
Maggi
C A
CA
Meli
A
A
D000818:Animals; D001980:Bronchi / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin / Q000494:pharmacology*; D004558:Electric Stimulation; D019004:Galanin; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009411:Nerve Endings / Q000187:drug effects*; D009475:Neurons, Afferent / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D009479:Neuropeptides; D010455:Peptides; D013779:Tetrodotoxin; D019004:Galanin; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin