Neurokinin A-(4-10): a potent bronchospastic agent virtually devoid of sialologic properties in anaesthetized guinea-pigs.

The ability of substance P, neurokinin A and its C-terminal fragment, neurokinin A-(4-10), to elicit NK-1 (salivation) and NK-2 (bronchospasm) receptor-mediated responses was investigated in anaesthetized guinea-pigs. Neurokinin A-(4-10) produced a dose-related increase in tracheal insufflation pressure and its maximal effect was similar to that elicited by neurokinin A and significantly greater than that of substance P. On the other hand substance P induced a potent dose-dependent increase of salivation while neurokinin A was significantly less potent. Neurokinin A-(4-10) did not exert any sialologic effect even at the dose of 100 nM/kg. These findings indicate that neurokinin A-(4-10) might be a valuable pharmacological tool for characterizing the involvement of NK-1 and NK-2 receptors in physiological responses in vivo.