The cholinergic receptors on the heart of the marine bivalve Meretrix lusoria were used as a model to investigate their pharmacological properties in bivalves. By recording method, we measured the contractile force (CF) and the heart rate (HR) of the heart to examine the characteristics of cholinergic receptors of a marine bivalve. The known ACh receptor agonists or antagonists in vertebrate nervous system were then introduced into the heart by perfusion, to monitor their effects upon heart activities. Of the six tested agonists, two mAChR agonists (OXA-22, bethanechol) and two nAChR agonists (methylcarbachol, nicotine) mimicked the response induced by ACh. Among the seven tested antagonists, three mAChR antagonists (trihexyphenidy1, atropine and scopolamine) and three nAChR antagonists (TEA, curare and hexamethonium bromide) showed the antagonistic effects on the inhibition induced by ACh. However, there was one mAChR agonist, metoclopramide, that behaved like an ACh antagonist. Both APE (mAChR agonist) and PTMA (nAChR antagonist) showed no significant effects. This differences suggest that the pharmacological characteristics of ACh receptors on the heart of bivalve are different from those in vertebrates. It may be a novel type of ACh receptors.

1993-01-01·The Chinese journal of physiology

Effects of neuroactive agents on the isolated heart activities of marine bivalve Meretrix lusoria.

Article

作者: Lin, J T ; Lee, C M ; Tsai, T S

By recording method, we measured simultaneously both the contractile force (CF) and the action potential (AP) of the isolated heart to confirm the chief cardioregulatory transmitters of a marine bivalve. The effects of several neuroactive agents on CF, HR and the amplitude of AP in marine bivalve were investigated. Acetylcholine and carbachol produced inhibitory effects on the heart performance at 1.0 x 10(-11) M. Choline also exhibited inhibitory effects at a higher concentration, but atropine, curare, pilocarpine and hexamethonium bromide (all at 1.0 x 10(-4) M) exerted no significant effects on the spontaneous cardiac activities. 5-HT and 8-OH-DPAT produced positive chronotropic and inotropic effects on the heart at 1.0 x 10(-8) M, whereas adrenaline and dopamine were positively inotropic at 1.0 x 10(-5) M. The perfusion of adrenaline or dopamine typically prolonged the plateau duration of the action potential, and then enhanced CF. However, histamine, GABA and PGF2 alpha all exerted no significant effect on either CF or the amplitude of AP of the isolated heart. The results indicate that 5-HT and acetylcholine are excitatory and inhibitory agents, respectively, that regulate the isolated cardiac performance in a marine bivalve. The mechanism of positively inotropic effects of biogenic amines is discussed.

1990-06-01·Journal of Applied Physiology3区 · 医学

Stimulation of tracheal ciliary beat frequency by capsaicin

3区 · 医学

Article

作者: Miller, I. F. ; Yeates, D. B. ; Wong, L. B.

To determine the possible involvement of neural and cyclooxygenase pathways whereby irritants might affect cilia activity in vivo, the temporal response of canine tracheal ciliary beat frequency (CBF) to the inhaled surrogate irritant capsaicin was studied. CBF was measured on the ventral midtracheal surface of barbiturate-anesthetized eucapnically ventilated beagle dogs by heterodyne-mode laser light scattering. After base-line CBF was established, hexamethonium bromide (2 mg/kg iv), ipratropium bromide (0.5 microgram/kg iv), indomethacin (2 mg/kg iv), or intravenous 0.9% saline was administered. Aerosolized 3 Z 10(-9) M capsaicin in 0.9% saline was delivered for 2 min, and CBF was measured for the following 60 min. Control experiments used 0.9% saline sham aerosol with a 0.9% saline sham block. Aerosolized capsaicin stimulated CBF from a base line of 6.2 +/- 1.4 (SD) Hz (n = 230) to a mean maximum of 17.7 +/- 7.3 Hz (n = 16) 23 min after aerosol delivery, and CBF returned to base line within 60 min. Neither hexamethonium bromide, ipratropium bromide, nor indomethacin changed CBF from base-line values. The episodic CBF stimulatory response to capsaicin after commencement of aerosol was completely inhibited by hexamethonium bromide. Ipratropium bromide partially inhibited the first 15 min and totally inhibited the following 45 min of stimulatory response. Indomethacin inhibited the initial 15 min but had less effect on the following 45 min of stimulatory response. These data indicate that multiple stimulatory mechanisms function over a prolonged period of time to affect the removal of irritants from the airways and that these mechanisms differ from those involved in the maintenance of basal CBF.

100 项与 Hexafluorenium bromide 相关的药物交易

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