Hexafluorenium bromide

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.

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.