Heavey ML, Lan WA, Pennefather JN. Tachykinin receptors mediating non-cholinergic contraction of the guinea-pig isolated main bronchus in response to field stimulation.
Clin Exp Pharmacol Physiol 1997;
24:673-9. [PMID:
9315368 DOI:
10.1111/j.1440-1681.1997.tb02111.x]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
1. The primary aim of the present study was to classify the receptors activated by tachykinins released by field stimulation of intramural nerve terminals of the guinea-pig isolated main bronchus by using the novel non-peptide NK1 and NK2 receptor-selective antagonists SR 140333 and SR 48968, respectively. 2. Log concentration-response curves to substance P (SP), the NK1 receptor-selective agonist [Sar9, Met(O2)11]-SP and the NK2 receptor-selective agonist [Nle10]-neurokinin (NK) A(4-10) were constructed in the presence of indomethacin (2 mumol/L) and phosphoramidon (5 mumol/L). Substance P was the least potent of these agonists. 3. In left and right main bronchi, SR 140333 (100 nmol/L) antagonized concentration-related contractions evoked by SP yielding pKB values of 8.02 and 7.68, respectively. SR 140333 (10 nmol/L) antagonized the effects of [Sar9, Met(O2)11]-SP on the left bronchus with a pKB value of 8.04. 4. SR 48968 (100 nmol/L) antagonized the effects of SP yielding pKB estimates of 7.88 (left bronchus) and 7.31 (right bronchus). 5. [Nle10]-NKA(4-10) was more potent in the left than in the right main bronchus. SR 48968 (0.1-10 nmol/L) antagonized the effects of [Nle10]-NKA(4-10) on the left bronchus with pKB estimates of 8.26-10.25. 6. In the presence of indomethacin (2 mumol/L), phosphoramidon (5 mumol/L) and atropine (1 mumol/L), electrical field stimulation (EFS; 30 V, 1 ms, 15 s at 1, 3, 10 and 30 Hz) produced prolonged contractions. SR 48968 (0.1 mumol/L) markedly reduced responses to stimulation, whereas SR 140333 (0.3 mumol/L) caused a small but significant rightward displacement of the log frequency-response curve. In combination, these concentrations of SR 48968 and SR 140333 produced complete inhibition to field stimulation at 10 Hz. 7. These results indicate that: (i) both NK1 and NK2 receptor subtypes are present in the guinea-pig main bronchi with the left bronchus being more sensitive to an NK2 receptor agonist; and (ii) EFS of the main bronchus leads to frequency dependent contractions due to the release of tachykinin(s) that predominantly activate an NK2 receptor.
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