Edward Aiello

Cilio-inhibitory effects of branchial nerve stimulation in the mussel, Mytilus edulis

Abstract 1. 1. Lateral ciliary activity was studied on isolated gill-branchial nerve-visceral ganglion preparations of the mussel Mytilus edulis . 2. 2. Electrical stimulation of the nerve at 2, 3, and 5 pulses per second and exposure to 5-hydroxytryptamine each accelerated ciliary beating. Each was blocked by prior treatment with bromolysergic acid diethylamide. 3. 3. Electrical stimulation of the nerve at 25 and 50 pulses period and exposure to dopamine each inhibited ciliary activity. Each was blocked by prior treatment with phenoxybenzamine. 4. 4. In addition to previously demonstrated cilio-excitatory fibres, the branchial nerve appears to contain cilio-inhibitory fibres with dopamine as a possible inhibitory neurotransmitter.

Endogenous dopamine in bivalve gills

Abstract 1. 1. Dopamine was identified in gill extracts of Modiolus demissus, Mytilus edulis and Modiolus modulus in concentrations ranging from 0·12 to 0·98 μg/g. 2. 2. Incubation of gills in 2 × 10 −4 M l -dopa for 2 hr resulted in a greater than tenfold increase in endogenous dopamine levels. 3. 3. Norepinephrine is apparently not present at levels comparable to those of dopamine.

An opioid mechanism modulates central and not peripheral dopaminergic control of ciliary activity in the marine mussel Mytilus edulis.

Summary1.Opioid receptors and enkephalinergic neurons in the central nervous system ofMytilus edulis have been reported. Also known is that the lateral epithelium of the gill is innervated by serotonergic, cilioexcitatory neurons and dopaminergic, cilioinhibitory neurons. The aim of the present report is to look for an effect of opioid agonists on the nervous control of the lateral cilia.2.Dopamine applied to the cerebral ganglion inhibited the activity of lateral cilia in the gill. This effect was blocked by the application of several opioids to the visceral ganglion. The block was reversed by the application of naloxone to the visceral ganglion.3.Dopamine applied to the visceral ganglion also inhibited lateral ciliary activity as shown earlier. Opioids applied to the visceral ganglion partially blocked this effect but this was overcome by higher concentrations of dopamine.4.Preparations with low endogenous rates of ciliary beating were stimulated by the application of opioids to the visceral ganglion. Naloxone blocked this effect.5.Preparations with high endogenous rates of ciliary beating were inhibited by the application of naloxone to the visceral ganglion.7.Electrical stimulation of the cerebrovisceral connective produced excitatory and inhibitory effects depending on the rate of stimulation. Morphine applied to the visceral ganglion diminished the cilioinhibitory effects and enhanced the cilioexcitatory effects of electrical stimulation.8.Morphine applied to the gill had no effect on the cilioinhibitory action of dopamine applied to the visceral ganglion. There was no observable effect of opioids applied to the gill and no alteration in the cilioinhibitory effect of dopamine or the cilioexcitatory effect of serotonin applied directly to the gill in the presence of opioids.9.Specific opioid binding sites were found in the visceral ganglion but were not found in gill, palp, mantle, or visceral mass tissue.10.A dopamine-stimulated adenylate cyclase activity was again found in the visceral ganglion and the gill. Etorphine reduced the dopamine stimulation of cyclase in the ganglion but not in the gill.11.It is postulated that a cilioinhibitory, dopaminergic mechanism includes nerves running from the cerebral ganglion to the gill with synaptic transmission in the visceral ganglion that can be modulated by opioids.

Ciliary function of the frog oro-pharyngeal epithelium.

SummaryThe palate epithelium of the frog was examined by scanning electron microscopy, light microscopy and high speed cine micrography. The cilia remain stationary for much of the time in the end-of-effective stroke position. Each beat cycle begins with a forwardly-directed recovery stroke lasting about 60 ms, followed by an effective stroke towards the oesophagus lasting about 12 ms. Activity can often be correlated with the presence of mucus, which is carried as strands on the tips of the ciliary effective strokes whilst the recovery strokes move beneath the mucus. Coordination of ciliary activity was very variable; local antiplectic metachrony of the recovery strokes could almost always be seen, and on very active epithelia effective strokes were associated with approximately diaplectic waves (either to left or right), but any particular pattern of coordinated activity was transient and quickly transformed to another pattern. Beating and coordination of these short cilia were compared with those of cilia propelling water.

Stimulation of frog ciliated cells in culture by acetylcholine and substance P

1. Ciliary beat frequency in epithelial outgrowths from cultured explants of Rana pipiens palate changed markedly from second to second. 2. Acetylcholine (10(-8) to 10(-3) M) and substance P (1.35 x 10(-7) to 1.35 x 10(-5) M) increased and stabilized ciliary beat frequency. The effect of acetylcholine and part of the effect of substance P were blocked by atropine (10(-4) M). 3. Acetylcholine appears to act directly and substance P both directly and indirectly through the release of acetylcholine.

A role for acetylcholine in the regulation of ciliary activity

Abstract 1. Low concentrations of acetylcholine and physostigmine were excitatory and high concentrations were inhibitory to lateral cilia of Mytilus edulis gill. 2. Physostigmine potentiated the effects of acetylcholine and nerve stimulation. 3. Bromolysergic acid diethylamide blocked excitation by acetylcholine, physostigmine, 5-hydroxytryptamine and 5 Hz nerve stimulation. 4. Phenoxybenzamine blocked inhibition by acetylcholine, physostigmine, dopamine and 50 Hz nerve stimulation. 5. It is postulated that acetylcholine affects ciliary beating by releasing endogenous mediators and that this is the principal physiological role of endogenous acetylcholine regarding ciliary activity in the gill.

Succinate metabolism in the gills of the mussels Modiolus demissus and Mytilus edulis

1. 1. Thin-later chromatographic evidence shows succinic acid as an anaerobic end-product of glycolysis in the gills of Modiolus demissus and Mytilus edulis. 2. 2. Sodium succinate stimulates oxygen consumption in intact gill pieces and in gill homogenates of both species. 3. 3. The stimulation of oxygen consumption by succinate in gill homogenates of both species is inhibited by sodium malonate. 4. 4. Oxygen consumption in gill homogenates of Modiolus, but not Mytilus, is stimulated following anaerobic incubation of intact gills, and this stimulation is blocked by malonate.

Anaerobic cilio-excitation and metabolic stimulation by 5-hydroxytryptamine in bivalve gill

Abstract 1. 1. 5-Hydroxytryptamine (5-HT) exerts a cilio-excitatory effect in the gills of Modiolus demissus and Mytilus edulis under the anaerobic conditions described. 2. 2. The anaerobic cilio-excitation can be blocked by the metabolic inhibitors of glycolysis, iodoacetate and fluoride. 3. 3. Anaerobic glycolytic rates, determined by standard manometric techniques, are markedly stimulated by 5-HT in Modiolus gill, and to a lesser extent in Mytilus gill. 4. 4. The addition of dextrose or adenosine triphosphate (ATP) and, to a greater extent, dextrose plus ATP produced increased rates of glycolysis in the gills of both species. 5. 5. 5-HT stimulated the dextrose- or the ATP-enhanced rates, but it had no stimulatory effect in the presence of dextrose plus ATP. 6. 6. Glycolytic rates of gill homogenates were also studied, and the effects of nicotinamide adenine dinucleotide (NAD), fructose-6-phosphate (F-6-P), and fructose-1,6-diphosphate (FDP) are reported. 7. 7. It is suggested, on the basis of indirect evidence, that 5-HT exerts its effect in this system by activating phosphoglucomutase.

Dual innervation of the foot and the control of foot movement by the central nervous system in Mytilus Edulis (Bivalvia)

Abstract 1. Nerve cutting experiments show that contraction and extension of the foot are controlled by the pedal ganglia. The cerebral ganglia exert a tonic influence tending toward extension; the visceral ganglia tend to cause contraction. 2. Application of dopamine, norepinephrine, epinephrine and acetycholine to the foot and ganglia causes contraction; application of 5-hydroxytryptamine causes extension. 3. Destruction of dopaminergic nerves by 6-hydroxydopamine prevents contraction; destruction of serotonergic nerves by 5,6-dihydroxytryptamine prevents extension. 4. Dual innervation of the foot and control of contraction by dopaminergic nerves and of extension by serotonergic nerves is proposed.

Substance P in the regulation of mucociliary transport in the frog palate

1. Mucociliary transport of carbon particles across the palate of anesthetized Rana pipiens was accelerated by electrical stimulation of the palatine nerve. 2. Transport was also accelerated by intracardiac injection of acetylcholine and of substance P in a dose-dependent manner. 3. Acceleration of transport by acetylcholine and by substance P was selectively blocked by atropine and by the substance P antagonist Spantide, respectively. 4. Acceleration of transport by nerve stimulation was blocked partially by atropine and by Spantide, and completely by the two administered concurrently. 5. It is concluded that nerve stimulation releases both acetylcholine and substance P or a similar neuropeptide. 6. Taken in conjunction with the literature, the data suggest that these substances are involved in the normal mechanism for stimulating mucociliary clearance of the palate in response to the presence of particles.