Kiyoaki Kuwasawa

Intrinsic and extrinsic neural and neurohumoral control of the decapod heart

The intra-cardiac nervous system of the decapod heart is composed of large and small ganglionic cells (LGCs and SGCs) and axons of extrinsic cardio-acceleratory and-inhibitory neurons (CAs and CIs). Candidate neurotransmitters for the neurons have been determined by pharmacological, cytochemical and immunocytochemical tests. SGCs may be cholinergic, LGCs and CAs are probably dopaminergic, and CIs are GABAergic. Serotonin and octopamine were cardio-excitatory neuromodulators of the heart. Proctolin, crustacean cardio-active peptide (CCAP), red pigment concentrating hormone (RPCH), and FMRFamide also had modulatory actions on the heart. Proctolin was the most potent peptide, which acted primary on the cardiac ganglion. Insect adipokinetic hormones had little effect on the heart.

A neuroanatomical and electrophysiological analysis of nervous regulation in the heart of an isopod crustacean,Bathynomus doederleini

Summary1.We have used anatomical, histological, and electrophysiological techniques to study the innervation of the heart of an isopod,Bathynomus doederleini.2.The heart beat was driven by a cardiac ganglion consisting of twelve morphologically identical neurones.3.The paired anterior cardiac nerves each contained five axons: three cardio-regulator axons, and two motor axons to anterior cardio-arterial valves.4.The functions of the cardio-regulator axons were elucidated by stimulating individually one inhibitor and two accelerator axons on either side.5.The two cardio-accelerator axons (on each side) were functionally identical. They innervated the cardiac ganglion, producing discrete EPSPs.6.The cardio-inhibitor axon induced discrete IPSPs in the cardiac ganglion. This axon may also directly innervate the myocardium.7.The two pairs of valve motor nerves each contained one excitor axon and one inhibitor axon. The excitatory innervation produced valve contraction resulting in a decrease of arterial dilation during systole. The inhibitory innervation produced valve relaxation resulting in an increase of arterial dilation.8.The valve axons may regulate the distribution of haemolymph among arteries. The cardiac output may be regulated by the nerves to the cardio-arterial valves and the cardio-regulator nerves to the heart.

Ganglionic activation of the myocardium of the lobster,Panulirus japonicus

Summary1.In the lobster heart, electrical activity of the cardiac ganglion cells, the thick ganglionic branches and the cardiac muscle cells were investigated by simultaneous recording from each pair of them.2.A thick ganglionic branch usually contained three axons and periodically generated bursts which usually consisted of three kinds of impulses (Figs. 2, 3 and 5). Cardiac muscle cells were activated by six or more axons as a result of overlapping innervation by two or more branches (Fig. 5).3.A single large ganglion cell, with its several axons extending through several different branches, innervated almost the whole heart (Figs. 2 and 4). Most cardiac muscle was activated by each of the large cells with overlapping innervation of two or more branches (Figs. 2, 4 and 5). Therefore, intracellular spike potentials in the soma of a large cell could often be linked to corresponding impulses in bursts of a certain branch (Fig. 6) and to a certain kind of EJPs in a muscle cell (Fig. 7).4.The delay between the spike recorded from large cells and EJP generation ranged from 8 to 20 ms as measured by simultaneous intracellular recording (Figs. 7 and 8).5.Cardiac muscle cells synchronously received two groups of periodic impulse trains, phasic and tonic (Figs. 2, 3 and 8 B). The 1st–4th large cells generated the phasic trains in bursts which corresponded with the large potentials in the cardiac muscle cells. The 5th large cell axons generated a tonic train throughout the burst, which gave rise to the small EJP train seen in muscle cells.6.The sustained potential in muscle burst discharges was attributable to electrotonic spreading of EJP trains caused by concurrent and repetitive firing of the large cell axons (Fig. 4).

Monoamines, amino acids and acetylcholine in the preoptic area and anterior hypothalamus of rats: measurements of tissue extracts and in vivo microdialysates

A microbore column high-performance liquid chromatography (HPLC) system was used to measure neurotransmitters in tissue extracts and in vivo microdialysates obtained from the preoptic area (PO) and anterior hypothalamus (AH) of rats. The extracts contained norepinephrine, epinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC), dopamine, 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), aspartate, glutamate, GABA, acetylcholine (ACh) and choline. The microdialysates obtained from the PO and AH of freely moving rats contained all of these substances except for norepinephrine, epinephrine, dopamine, and 5-HT. During collection of microdialysate from the PO and AH, core body temperature and locomotor activity were simultaneously measured by means of telemetry. The locomotor activity and body temperature increased during the night. This was accompanied by increased levels of 5-HIAA. The results suggest that serotonergic neuronal mechanisms in the PO and AH may be involved in hypothalamic regulation of spontaneous behaviors and body temperature.

Neural control of the cardio-arterial valves in an isopod crustacean, Bathynomus doederleini: excitatory and inhibitory junctional potentials

Summary1.InBathynomus doederleini, there are cardio-arterial valves at the junctions between the heart and the arteries. These comprise: one anterior median artery, a pair of anterior lateral arteries and five pairs of lateral arteries.2.The valves at the cardiac junctions of the three anterior arteries receive innervation from a pair of anterior cardiac nerves. The anterior cardiac nerve on each side contains one excitatory and one inhibitory motor axon for the valves.3.Excitatory junctional potentials (EJPs) were recorded from all three valves of the anterior arteries. Inhibitory junctional potentials (IJPs) were recorded from the valves of the pair of anterior lateral arteries, but not from the valve of the anterior median artery.4.A whole-mount preparation treated with glyoxylic acid developed fluorophore processes on all three valves of the anterior median and lateral arteries, suggesting that the processes are due to a pair of aminergic excitatory valve nerves.5.The lateral arterial valves receive innervation from the valve nerves running alongside the arteries. Each of the valves of the lateral arteries are innervated by inhibitory motor nerves producing IJPs in the valves, and probably only by these nerves.6.It is suggested that the flow of haemolymph to individual arteries is regulated by three types of innervation of the cardio-arterial valves. These are: dual innervation by excitatory and inhibitory axons, and single innervation which may be either excitatory or inhibitory.

Electrophysiological studies on the branchial ganglion in the opisthobranch molluscs (Aplysia andDolabella)

Summary1.The branchial ganglion of the gills ofAplysia kurodai, A. juliana andDolabella auricularia were investigated, using electrophysiological techniques.2.The branchio-ganglionic neurons (BGNs) generated spontaneous tonic impulses with superimposed pacemaker potentials and mainly periodic bursting impulses superimposed on slow sustained depolarizing potentials.3.BGNs were synchronously active, coupled one to another through bidirectional electrical synapses.4.Electrical stimulation of the branchial nerve elicited excitatory postsynaptic potentials (EPSPs), in BGNs, which showed facilitation and summation and were blocked with high Mg2+ sea water, indicating that the EPSPs were chemically mediated.5.Electrical stimulation of a nerve extending posterior to the ganglion also produced EPSPs in BGNs. These EPSPs showed summation (but not facilitation), and were blocked with high Mg2+ sea water, indicating that the EPSPs were chemically mediated.6.Tactile stimulation to the pinnule exerted excitatory transmission of EPSPs which caused BGNs to fire a burst of impulses, and resulting in a reflexive pinnule contraction.7.Electrical stimulation applied to a nerve of the branchial ganglion produced inhibitory postsynaptic potentials (IPSPs) which showed summation and had a reversal potential at a level slightly higher than the resting membrane potential. The inhibitory transmission seems to be from the mechanoproprioceptor in the gill, since it was elicited by a spontaneous gill contraction or by perfusion of the branchial vasculature with sea water.8.When either spontaneous bursts of the BGNs occurred, or bursts of BGNs were induced by intracellular current application, EJPs were evoked in the pinnule muscle. Thus, the peripheral nervous system including the branchial ganglion may contain motor neurons of the pinnule muscle.9.The branchial ganglion had functions of the peripheral reflex center and the distributing center of central motor influence to the branchial muscle.

The cardio-regulator nerves of the hermit crabs: anatomical and electrophysiological identification of their distribution inside the heart

Summary1.The cardiac ganglion and the routes of the cardio-regulator nerves inside the heart were investigated anatomically and electrophysiologically in the hermit crabs (Aniculus aniculus andDardanus crassimanus). It was proved that the dorsal cardiac nerve containing three regulator axons on each side, one inhibitor and two accelerators, pierced the heart wall and connected with the cardiac ganglion.2.The cardiac ganglion consisted of five large neurons and four small neurons. Configuration of the cardiac ganglion was analogous to the crab (Cancer orPortunus) cardiac ganglion in having a pair of circular trunks. However, arrangement of the large cells and the small cells was analogous to the lobster (Homarus, Panulirus orPalinurus) cardiac ganglion in alignment of the ganglionic cells.3.The two acceleratory nerves had almost identical innervating routes. The route of the inhibitory nerve was significantly different from the routes of the acceleratory nerves inside the heart.4.The inhibitory axon had the route only along the main trunk of the cardiac ganglion. IPSPs were recorded from large ganglionic cell bodies, one-toone to inhibitory impulses.5.The acceleratory axons were carried not only in the main trunk but also in the circular trunk. There were acceleratory branches extending toward the periphery away from both the trunks.6.EPSPs were recorded from large cell bodies in a one-to-one relationship to acceleratory stimuli. This provided direct evidence for ordinary synapses of the accelerator on the large ganglionic cells.

Periodic bursts in large cell preparations of the lobster cardiac ganglion (Panulirus japonicus)

Abstract 1. 1. Periodic bursts of pacemaker or follower type were recorded from the cells of the isolated trunk portions containing large somata or only a single soma. 2. 2. They changed in frequency with polarization levels of the soma caused by currents applied, disappearing at a certain hyperpolarization level. In the pacemaker type burst, the change was associated with the slope of the gradual depolarization preceding the burst. 3. 3. A burst was induced by the pulse of adequate strength applied at later interburst phase, its latency becoming less as the phase became later. The burst reset the normal rhythm. In the pacemaker type burst, the latency was associated with the slope of the local response due to the pulse. 4. 4. Spontaneous spikes in train responded to long currents or pulses essentially in the same manner as the periodic burst of pacemaker type. Often a local response appeared on the intimate relation to the spike initiation. 5. 5. Formation of periodic bursts in large cells was considered with special reference to initiation of the spontaneous slow potential and repetitive spikes.

A physiological saline for Lepidopterous insects: Effects of ionic composition on heart beat and neuromuscular transmission

Abstract Three species of Lepidoptera, Bombyx mori, Agrius convolvuli and Antheraea yamamai were used to prepare a suitable physiological saline for maintaining heart beat and junctional potentials of somatic muscle cells. A variety of salines designed for Lepidoptera were reexamined. Heart beat in the three species could not be maintained in salines used previously as physiological or culture solutions for Lepidoptera. Ionic compositions were determined for physiological salines that were suitable for maintaining the normal heart beat and normal neuromuscular transmission in body muscle cells. It was found that salines should contain 12–28 mM NaCl, 32-16 mM KCl ([Na+] + [K+ ] = 44) and at least 9 mM CaCl2. In the salines, stimuli to motor nerves evoke action potentials of more than 40 mV in amplitude in ventral muscle cells. The ionic composition of a new physiological saline for Lepidoptera is as follows: NaCl, 12–28; KCl, 32-16([Na+] + [K+] = 44); CaCl2, 9; NaH2PO4, 1.5; Na2HPO4, 1.5; MgCl2, 18; sucrose, 175 (mM), pH 6.5.

Neural pathways for cardiac reflexes triggered by external mechanical stimuli in larvae of Bombyx mori

Abstract Stimuli applied to mechano-exteroceptors induce the following five types of reflex cardiac responses in larvae of Bombyx mori. (1) Tactile stimuli applied to sensillar setae of the anal proleg induce antidromic heartbeat. (2) The stimuli simultaneously inhibit orthodromic heartbeat. These stimuli increase the heart rate if applied during a phase of antidromic heartbeat. The visceral nerve arises from the frontal ganglion. The anterior cardiac nerves branching out of the visceral nerve were found to trigger antidromic heartbeat. Posterior cardiac nerves branching out of the visceral nerve are the inhibitory motor nerves which inhibit orthodromic heartbeat. These posterior cardiac nerves also contain motor nerves for alary muscles in the 2nd abdominal segment. (3) Contraction of the alary muscle increases heart tone and results in acceleration of antidromic heartbeat. (4) Tactile stimuli to the antennae accelerate orthodromic heartbeat. The motor pathway is through the paired dorsal nerves of the 1st abdominal ganglion in a segment which lacks a pair of alary muscles. (5) Contraction of the alary muscles in the 7th and 8th abdominal segments evoked by these stimuli contributes to acceleration of the orthodromic heartbeat. The motor pathways for this are in the paired dorsal nerves of the 7th abdominal ganglion.