Modulation of neurotransmission in guinea-pig airways by galanin and the effect of a new antagonist galantide

Abstract

Galanin is localised to sensory nerve fibres and cholinergic nerves in airways. Galantide has been shown to be a novel high affinity antagonist to galanin, since it inhibits galanin-mediated inhibition of glucos-induced insulin secretion and the neuronal action of galanin in the brain. We investigated the effects of galanin on cholinergic and non-adrenergic, non-cholinergic (NANC) responses to electrical field stimulation in guinea-pig airways, and examined whether galantide antagonised the effect of galanin on neurotransmission. Galanin (10 −6M) had no effect on cholinergic bronchoconstrictor responses and inhibitory NANC relaxation responses in trachea, but significantly inhibited excitatory NANC bronchoconstrictor responses in bronchi which is due to the release of tachykinins. Galantide (10 −8–10 −6M) had no effect on the galanin-induced inhibition of the excitatory NANC responses. Galanin may be important in the modulation of excitatory NANC responses but not cholinergic and inhibitory NANC responses in guinea-pig airways. This modulatory effect may be via a different type of galanin receptor than is present in other organs.