Effects of leech Retzius cells on body wall muscles

Mason, Adrian; Sunderland, Andrew; Leake, L.D.

doi:10.1016/0306-4492(79)90086-8

Cited by 29 publications

(15 citation statements)

References 12 publications

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“…A dose-response curve (Cline, 1983) revealed that isolated ganglia from Hirudo have the capacity to synthesize 1000 times more GABA when exposed to 10 mM glutamate, used in this study, than when exposed to 0.02 mM glutamate, used by Henderson. Considering the complex role of the Retzius cells in leech physiology (Glover, 1984;Lent, 1977;Willard, 1981) in particular nerve-muscle interactions (Mason and Kristan, 1982;Mason et al, 1979) it is of interest that the Retzius cells synthesize and release GABA in addition to 5-HT.…”

Section: Discussionmentioning

confidence: 99%

Evidence for GABA as a neurotransmitter in the leech

Cline¹

1986

J. Neurosci.

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In the leech, Hirudo medicinalis, the inhibitory motor neurons to the longitudinal muscles in the body wall, cells 1 and 2, are linked via central inhibitory synapses to the excitatory motor neurons innervating the same muscles. Examination of these synapses showed that the inhibitors are GABAergic according to several electrophysiological and pharmacological criteria. Presynaptic release of neurotransmitter during passage of depolarizing current into the inhibitors, as well as direct application of GABA to the excitor cell bodies, hyperpolarizes the postsynaptic excitor. Moreover, both synaptic and extrasynaptic GABA receptors of the excitors are specifically blocked by the GABA antagonist bicuculline methiodide. The inhibitors, dissected from the ganglion and grown in culture, synthesize GABA when exposed to the GABA precursor glutamate, whereas the excitors do not synthesize detectable levels of GABA under these same conditions. The innervation and neurotransmitter sensitivity of the longitudinal muscles in the body wall of the glossiphoniid leeches Haementeria ghilianii and H. oficinalis were examined in order to determine if the inhibitory neurotransmitter at the neuromuscular junction is GABA. Individual muscle fibers are innervated by both inhibitory and excitatory motor neurons in a manner such that the inhibitory and excitatory nerve terminals and neurotransmitter receptors are spatially and electrically separate. Intracellular recordings taken from the muscle fibers reveal a resting potential of about -70 mV. The amplitude of the spontaneous inhibitory junctional potentials (IJPs) falls to zero at a polarization of about -65 mV and reverses in sign at the normal resting potential. Application of GABA to inhibitory junctional sites results in an increased conductance of the muscle fiber membrane and a polarization with a reversal potential of about -65 mV. Bicuculline methiodide blocks reversibly the GABA response and all spontaneous IJPs, without blocking the spontaneous excitatory junctional potentials (EJPs) recorded from the excitatory junctional sites.

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Section: Discussionmentioning

confidence: 99%

Evidence for GABA as a neurotransmitter in the leech

Cline¹

1986

J. Neurosci.

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“…The largest and best studied neurons in the leech central nervous system are the paired serotonergic Retzius neurons (cell body in diameter 50-70 µm), which induce mucus secretion [19] and are involved in motor control [21] and feeding behaviour [18]. The Retzius neurons of isolated ganglia are non-bursting neurons with a low spontaneous firing rate (<1 Hz).…”

Section: Introductionmentioning

confidence: 99%

Bursting activity in leech Retzius neurons induced by low external chloride

Beck

Lohr

Nett

et al. 2001

Pfl�gers Archiv European Journal of Physiology

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We have investigated the bursting activity of Retzius neurons in the central nervous system of the leech Hirudo medicinalis as induced in Cl(-)-free saline by measuring membrane potential, membrane current and the intracellular calcium concentration ([Ca2+]i), using fura-2 or Oregon-Green488-Bapta-1. The Retzius neurons changed their low tonic firing to rhythmical bursting activity when the extracellular Cl- concentration ([Cl-]o) was lowered to 1 mM or less. In Cl(-)-free saline (Cl- exchanged by gluconate), bursting was accompanied by a rise in intracellular Ca2+ in both cell body and axon, which oscillated in synchrony with the bursts. The Ca2+ transients depended on the amplitude and duration of the depolarization underlying the burst, and were presumably due to Ca2+ influx through voltage-dependent Ca2+ channels. In Ca(2+)-free, EGTA-buffered saline or in the presence of Ca2+ channel blockers verapamil (1 mM) or diltiazem (500 microM) the depolarizations underlying the bursts in Cl(-)-free saline were enhanced in amplitude and duration. Bursting was not affected by depleting the intracellular Ca2+ stores with cyclopiazonic acid. The depolarization in Cl(-)- and Ca(2+)-free saline did not evoke intracellular Ca2+ changes. The burst-underlying membrane depolarization induced by Cl- removal was found to be due to a Na(+)-dependent persistent inward current and could be inhibited by saxitoxin (25-50 microM). The results suggest that a persistent Na+ current is generated in Cl(-)-free saline and induces the depolarization underlying rhythmic activity, and that presumably Ca(2+)-induced K+ currents modulate the bursting behaviour.

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“…Not only are they recognizable by their shape and position in the ganglion, but much is already known of their biochemistry: they have been shown to contain 5-hydroxytryptamine (5-HT), and no other biogenic amines (Rude, Coggeshall & Van Orden, 1969;Stuart, Hudspeth & Hall, 1974;Osborne, Briel & Neuhoff, 1972;McCaman, Weinreich & McCaman, 1973) and to synthesize it from tryptophan and from its immediate precursor, 5-hydroxytryptophan (5-HTP) (Hildebrand, Barker, Herbert & Kravitz, 1971;Sargent, 1977). In addition, stimulation of these cells elicits 5-HT release (Willard, 1981), and exogenous 5-HT can mimic some of the effects of Retzius cell stimulation (Lent, 1973;Mason, Sunderland & Leake, 1979). Together, these results indicate that 5-HT is a transmitter released by Retzius cells in vivo.…”

Section: Introductionmentioning

confidence: 99%

The role of 5‐hydroxytryptamine as a transmitter between identified leech neurones in culture.

Henderson¹

1983

The Journal of Physiology

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SUMMARY1. The synthesis, storage, release and synaptic actions of 5-hydroxytryptamine (5-HT or serotonin) were studied in order to characterize the synaptic connexion that develops between pairs of identified neurones dissected from the central nervous system of the leech and maintained in culture. Experiments were made with Retzius cells (which are known to contain 5-HT in vivo) and pressure sensory neurones on which they form chemical synapses in culture.2 When incubated with [3H]5-HT and washed, Retzius cells in culture accumulatedapproximately 100 times more labelled 5-HT than did non-serotonergic cells, and 10 times more than Retzius cell somata acutely isolated from the animal and incubated in vitro. Chlorimipramine, a blocker of5-HT uptake, decreased the amount of[3H]5-HT accumulated by Retzius cells and also caused a reversible increase in the amplitude of the synaptic response in the pressure sensory cell elicited by stimulation of the Retzius cell. 5. Pressure sensory neurones in culture and in vivo responded to 5-HT focally applied by pressure ejection from a micropipette. Small pulses elicited a small, slow hyperpolarization. This response was due, at least in part, to an increase in chloride conductance and desensitized rapidly. With larger pulses, a larger, faster nondesensitizing depolarization was elicited.6. Together, these results provide evidence that 5-HT released from Retzius cells could be responsible for the chemical synaptic potentials seen in pressure sensory neurones in culture.

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Effects of leech Retzius cells on body wall muscles

Cited by 29 publications

References 12 publications

Evidence for GABA as a neurotransmitter in the leech

Evidence for GABA as a neurotransmitter in the leech

Bursting activity in leech Retzius neurons induced by low external chloride

The role of 5‐hydroxytryptamine as a transmitter between identified leech neurones in culture.

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