Changes in efferent activities of the gastric vagus nerve by administration of glucose in the portal vein.

Injection of glucose in the portal vein, as well as in the left carotid artery, brought a transient decrease in efferent discharges of the gastric vagus nerve, whereas venous injection of regular insulin brought a gradual increase in the discharges.     

Captivity affects behavioral physiology: plasticity in signaling sexual identity

Little is known about the link between captivity, physiology, and behavior in wild-caught vertebrates. Anecdotal evidence suggests that hormonal changes are responsible for behavioral changes in wild animals brought into captivity. Studying the effects of captivity on reproduction is hampered because wild animals often fail to exhibit sexual behavior under captive conditions. In weakly discharging electric fish, field studies have reported sex differences in electric organ discharges which are rarely seen in the laboratory. I now report the results of a series of laboratory investigations which show that Gnathonemus petersii exhibits seasonal, hormone-dependent, phase-specific sex differences in electric organ discharges. Captivity dramatically alters and may even reverse these sex differences as a result of rapid changes in endogenous plasma hormone levels. These findings have broad implications for research on animal physiology and behavior performed in laboratory settings.     

Captivity affects behavioral physiology: Plasticity in signaling sexual identity

Summary Little is known about the link between captivity, physiology, and behavior in wild-caught vertebrates. Anecdotal evidence suggests that hormonal changes are responsible for behavioral changes in wild animals brought into captivity. Studying the effects of captivity on reproduction is hampered because wild animals often fail to exhibit sexual behavior under captive conditions. In weakly discharging electric fish, field studies have reported sex differences in electric organ discharges which are rarely seen in the laboratory. I now report the results of a series of laboratory investigations which show thatGnathonemus petersii exhibits seasonal, hormone-dependent, phasespecific sex differences in electric organ discharges. Captivity dramatically alters and may even reverse these sex differences as a result of rapid changes in endogenous plasma hormone levels. These findings have broad implications for research on animal physiology and behavior performed in laboratory settings.     

Demonstration of generators of the locomotor and respiration rhythms in the cervico-thoracic spinal cord of rabbits

In curarized Rabbits whose cervico-thoracic cord has been isolated through C2 and Th12 transections, a pharmacological activation (nialamide-DOPA) disclosed distinct rhythmic efferent activities, locomotor-like bursts in forelimb muscle nerves and "respiratory" discharges in the phrenic nerves: they originate respectively from a cervico-thoracic locomotion generator and from a "respiration" generator; these spinal generators appear to be interconnected with each other.     

Preliminary results on the abiotic synthesis of metalloporphyrins]

The possibility of obtaining metalloporphyrins in abiotic conditions was investigated. The direct formation of zinc-porphyrins in the reaction product obtained by exposing a mixture of methane, ammonia and water vapor to electrical discharges is reported.     

4-aminopyridine and barium chloride attenuate the anti-epileptic effect of carbamazepine in hippocampal slices

The exact mode of action of the anti-epileptic agent carbamazepine is unknown. In hippocampal slices in which epileptiform discharges were induced by addition of penicillin to the perfusion medium, the depressant effect of carbamazepine was attenuated by the potassium-channel blockers barium chloride (0.1 mM) and 4-aminopyridine (200 microM), which suggested that potassium fluxes might be involved in the mechanism of action of carbamazepine.     

Cardiac activation and inhibition involved in molting behavior of a spiny lobster

To study the molting behavior of the spiny lobster, electrical activity of the heart, stomach and skeletal muscles was recorded using in-dwelling electrodes. For 1–2 h before molting the heart rate gradually increases. At the same time shorter trains of stomach burst discharges frequently occur. The heart rate then declines and burst discharges of skeletal muscles begin. The skeletal bursts are regularly spaced (10–15 s intervals). A peristalsis pattern of short and long bursts continues for 10–20 min and is terminated by a few bursts corresponding to abdominal flips. The short skeletal burst is followed by a drop in heart rate. Bioassay using the isolated heart suggests that at the final stage of molting the blood contains some substance(s) which inhibit heart beat.     

Testosterone changes the electric organ discharge and external morphology of the mormyrid fish, Gnathonemus petersii (Mormyriformes)

Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ discharge of the weakly electric African mormyrid, Gnathonemus petersii, were investigated. Within seven days of implantation, the duration of the discharge increased dramatically while the associated peak power frequency of the Fourier spectrum decreased in all treated fish. By day 35, hormone-treated fish exhibited up to five-fold increases in EOD duration, as well as multiple discharges and variations in the shape of the positive phase of the discharge. Testosterone treatment also changed body morphology, making immature and adult female fish resemble adult males.     

Tele-encephalic versus cerebellar control upon ponto-geniculo-occipital waves during paradoxical sleep in the cat.

Studying the effects that removal of the cerebellum and the frontal lobes had upon the phasic activities (PGO waves) of paradoxical sleep in the cat, it is shown that in this phase of the sleep-wakefulness cycle the cerebellum exerts an inhibitory action upon the amplitude of the GPO, while the frontal lobes influences the pattern of their discharges.     

Paroxysmal discharges in the electroencephalogram of the El mouse

Summary The spike discharges in the EEG of the El mouse, a seizure-susceptible strain, were recorded during convulsive seizures. This fact provides evidence that those seizures are really epileptic convulsions.I thank Dr.K. Imaizumi and Dr.K. Nakano of National Institute of Health for their sharing the strain of El mouse to us and MissY. Nakamoto and Mr.N. Ozawa for their technical assistance and Mr.K. Moriyama for his care for the mice, and also thank Dr. H.Narabayashi for his criticism on this paper.     

Medial forebrain bundle projections to the nucleus of the diagonal band of Broca.

The electrophysiological characteristics of the medical forebrain bundle (MFB) projections to the nucleus of the diagonal band of Broca (nDBB) were studied in acutely prepared cats. MFB stimulation evoked field potentials which consisted of a large negative wave followed by a shallow positivity. Extracellular unitary discharges appeared out of the negativity. In addition, intracellularly recorded EPSPs showed no significant shift in the latency to onset with changes in stimulus intensity. These observations indicate that at least some of the MFB projections to the nDBB are excitatory with respect to their target cells.     

AfricanClarias catfish elicits long-lasting weak electric pulses

The African catfishClarias is generally considered to possess electroreceptors but not electric organs. It is reported here that at least one species of the genus,C. gariepinus, can produce weak monophasic discharges during aggressive interactions with conspecifics. These irregular pulse discharges are substantially longer than the electric organ discharges (EODs) of all other pulse-generating freshwater electric fishes. It is also shown that the optimal sensitivity ofClarias' ampullary receptors just corresponds to the modal pulse duration. TheClarias catfish, with its very specific EOD, may be of special interest in the evolution of the electrogenic system in the siluriforms, comprising many electroreceptive but nonelectrogenic catfish species.     

4-Aminopyridine and barium chloride attenuate the anti-epileptic effect of carbamazepine in hippocampal slices

Summary The exact mode of action of the anti-epileptic agent carbamazepine is unknown. In hippocampal slices in which epileptiform discharges were induced by addition of penicillin to the perfusion medium, the depressant effect of carbamazepine was attenuated by the potassium-channel blockers barium chloride (0.1 mM) and 4-aminopyridine (200 M), which suggested that potassium fluxes might be involved in the mechanism of action of carbamazepine.     

Inhibitor interneurons of horizontal ocular saccades studied in the alert cat with the aid of intra-axonal injections of peroxidase

A simultaneous study of the functional and morphological characteristics of burst inhibitory neurons (B.I.N.) has been performed in the alert cat. For the first time, in the central nervous system of mammal, extra- and intracellular records have been coupled with intra-axonal injection of H.R.P. in the alert animal. The B.I.N. discharge during saccades and the quick phase of vestibular and optokinetic nystagmus oriented toward the ipsilateral side of recording. The frequency of discharges is proportional to the eye angular velocity. The axons end on the abducens motoneuron. Collaterals reach the controlateral prepositus hypoglossi nucleus, medial vestibular nucleus and reticular nuclei.     

The effects of topical succinylcholine on single unit and electrocorticographic activity

Summary Topical succinylcholine induces massive epileptiform discharges in the electrocorticogram, coinciding with the bursting or tonic activity of single cortical cells.     

Suppression,chez le Lapin,des effects locomoteurs de la DOPA par le diethyldithiocarbamate

Summary Mesencephalic, curarized rabbits can develop locomotor discharges with alternating phases of flexions and extensions in hind limb nerves.Moreover, DOPA was shown to exaggerate the extensor activity as compared to that in the flexor. It is shown here that diethyldithiocarbamate, a dopamine--hydroxylase inhibitor, suppresses discharges in extensor nerves and that a subsequent injection of DOPA isgenerally no more active. It is concluded that the supraspinal extensor activation in locomotion is depending upon synthesis of norepinephrine and not that of dopamine.     

Possible explanation for interictal-ictal transition: evolution of epileptiform activity in hippocampal slice by chloride depletion.

In thin hippocampal slices, paroxysmal epileptiform discharge was generated in high potassium medium. Removal of chloride from the high potassium medium caused explosive potentiation of the paroxysmal discharge and emergence of clonic relapsing discharges. Evolution of the paroxysm to regenerative seizure was attributed to the reduction of inhibitory postsynaptic potentials.     

Possible explanation for interictal-ictal transition: Evolution of epileptiform activity,in hippocampal slice by chloride depletion

Summary In thin hippocampal slices, paroxysmal epileptiform discharge was generated in high potassium medium. Removal of chloride from the high potassium medium caused explosive potentiation of the paroxysmal discharge and emergence of clonic relapsing discharges. Evolution of the paroxysm to regenerative seizure was attributed to the reduction of inhibitory postsynaptic potentials.     

Effects of D-glucose anomers on afferent discharge in the hepatic vagus nerve

Summary Intraportal injections of -D-glucose, optically equilibrated D-glucose and -D-glucose reduced afferent discharges in the hepatic vagus nerve of anaesthesized rats. -D-Glucose was most potent in decreasing the discharge.     

Effect of testosterone on the kinetics of the development of suppressor cells in adjuvant arthritis

The induction of unresponsiveness to mycobacterial adjuvant took a longer time in male DA rats than in female rats. A shift in the induction time of unresponsiveness in males toward the female type was brought about by castration, but could be reverted to the male type by the application of testosterone. The transfer study revealed that cells capable of preventing arthritis required a longer incubation time for their development in males than in females. This suggests that testosterone inhibits the development of suppressor cells in adjuvant arthritis.