Biomedical subjects

A Inokuchi

Publications and source records attributed to A Inokuchi.

At least 37 records · Page 2Linked to original sources

PubMed1997

[Quantitative analysis of the gustatory evoked potentials in the guinea pig].

Gustatory evoked potentials were studied in anesthetized guinea pigs to develop an objective and quantitative taste examination for patients with taste disorders. A positive wave was recorded by the application of NaCl, HCl or quinine hydrochloride solution. There was little difference in latency, duration and waveform among these three solutions. No apparent change in activity was seen after the application of sucrose solution or distilled water. The gustatory evoked potentials that excluded the influence of the trigeminal nerve innervating the tongue surface were able to be reproducibly recorded on either the cortical surface or the skull surface. There was a linear relationship between logarithmic values of potential amplitude and those of taste solution concentration. Therefore, it is suspected that the quantitative evaluation of taste detection is possible by measuring the taste solution concentration-potential amplitude relationship.

Animals↗

PubMed1995

Disturbance of regulation of sodium by cis-diamminedichloroplatinum in perilymph of the guinea pig cochlea.

We studied the acute effects of cis-diamminedichloroplatinum (CDDP) on the cochlear partition and inner ear fluid in the guinea pig. At 48 hours after the administration of a single intramuscular injection of CDDP, 12.5 mg/kg of body weight, the endocochlear resting potential (EP) was significantly decreased to 32.1 +/- 1.8 mV in the treated animals, versus 80.6 +/- 1.0 mV in the control animals. There was a significant rise in potassium (K+), sodium (Na+), and chlorine (Cl-) in the endolymph of the animals treated with CDDP as compared with the control animals. Only Na+ was found to increase significantly in the perilymph, reaching more than twice the level of the control animals; both K+ and Cl- remained within the normal range. Serum electrolytes also remained within the normal range. Evaluation of modified ionic permeabilities across the endolymph-perilymph barrier showed an apparent increase in Na+ permeability and a normal range of K+ and Cl- permeabilities. Histopathologic examination of the cochlea showed a moderate collapse of the endolymphatic space, with atrophy of the stria vascularis and destruction of the outer hair cells. The findings suggest that the acute changes produced in the cochlea by administration of CDDP were attributable to a breakdown in the regulation of Na+ metabolism in the perilymph.

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PubMed1994

Effects of stimulation of the vestibular nuclei on posterior hypothalamic neuron activity in guinea pigs.

To clarify the differences among the four main vestibular nuclei in the vestibulo-autonomic reflex, we examined the effects of electrical stimulation of superior, lateral, medial and descending vestibular nuclei (SVN, LVN, MVN and DVN) on posterior hypothalamic area (PHA) neurons in the guinea pig. Ipsi- and contralateral SVN stimulation produced excitation in 30% and 25% of the PHA neurons tested, respectively. Twenty percent of the PHA neurons showed an excitatory response to ipsilateral LVN stimulation while 60% of the neurons tested responded to contralateral LVN stimulation, including excitation of 36% and inhibition of 24%. MVN and DVN stimulation produced little change in PHA neuron activity. These findings suggest that vestibular information processed in the SVN and the LVN is conveyed to the hypothalamus and may then contribute to activation of the vestibulo-autonomic reflex.

Animals↗

PubMed1993

Purification and characterization of membrane-bound CO-reactive hemoprotein from Tetrahymena pyriformis mitochondria.

A CO-reactive hemoprotein was purified from the mitochondrial membrane fraction of Tetrahymena pyriformis. It showed absorption peaks at 615 and 455 nm in the reduced form and an alpha peak at 565 nm in the pyridine ferrohemochrome spectrum. Although the spectral properties were apparently similar to those of 'cytochrome a620' which was previously proposed as a mitochondrial terminal oxidase in T. pyriformis, it did not contain any molecules of heme a or copper atoms. Further, it showed neither cytochrome c oxidase nor cytochrome c peroxidase activity. These results suggest that 'cytochrome a620' may not be the terminal oxidase in the mitochondrial respiratory chain of T. pyriformis.

Animals↗

PubMed1993

Convergence of olfactory and nasotrigeminal inputs and possible trigeminal contributions to olfactory responses in the rat thalamus.

To elucidate the role of trigeminal input on the olfactory system, field-evoked potentials were measured following electrical stimulation of the nasociliary branch of the trigeminal nerve in the olfactory-related structures in the rat brain. Significant potential changes were recorded in the mediodorsal nucleus of the thalamus and the lateral hypothalamic area. In the mediodorsal nucleus of the thalamus, the neurons responding to olfactory bulb electrical stimulation also responded to trigeminal nerve stimulation. Single neuronal responses of mediodorsal thalamic neurons following odorant stimulation were enhanced by blockade of the trigeminal nerve with procaine. These results suggest that olfactory and trigeminal pathways converge on the same neural elements within the mediodorsal nucleus of the thalamus and that the trigeminal input may modulate olfactory input in this nucleus.

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PubMed1991

Vestibular evoked potentials to angular acceleration in the guinea pig. A preliminary report.

Rotational evoked potentials were studied in the guinea pig under urethane anesthesia. The stimulus events were triangular velocity changes produced by abrupt reversals of acceleration, and horizontal semicircular canals were stimulated. A positive-negative-positive wave was recorded in the vestibular nuclei and the potential was totally abolished after bilateral labyrinthectomy. Single unit recordings revealed that the peak latency of the negative wave is almost coincident with the peak latency of the excitation of type I vestibular nucleus neurons. It is concluded that the recorded potential to the rotational stimuli in this experiment is of vestibular origin.

Acceleration↗

PubMed1988

Effects of locus ceruleus and olfactory bulb stimulation on rat olfactory tubercle neuron activity.

The effects of electrical stimulation of the olfactory bulb and the locus ceruleus on olfactory tubercle neurons were examined in rat models. Ipsilateral stimulation of the olfactory bulb produced excitation in 31% of olfactory tubercle neurons tested and inhibition in 17%. Twenty-two percent of the olfactory tubercle neurons were excited, whereas 9% were inhibited by ipsilateral stimulation of the locus ceruleus. Contralateral stimulation of the locus ceruleus produced similar responses in the same neuron entities. A negative-positive evoked potential was recorded in the olfactory tubercle after ipsilateral and contralateral stimulation of the locus ceruleus. Thirty-three percent of the olfactory tubercle neurons that responded orthodromically or antidromically to stimulation of the olfactory bulb were excited by ipsilateral stimulation of the locus ceruleus. In contrast, only 10% responded with excitation to ipsilateral stimulation of the locus ceruleus among the olfactory tubercle neurons that were unresponsive to stimulation of the olfactory bulb. These findings suggest that olfactory tubercle neurons that receive input from or sending output to the olfactory bulb are influenced by the noradrenergic system of the locus ceruleus. A possible role of the olfactory tubercle in olfactory transduction will also be discussed.

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PubMed1987

Projections from the ventral tegmental area to the olfactory tubercle in the rat.

The projection between the ventral tegmental area (VTA) and the olfactory tubercle (OT) was examined electrophysiologically in the rat. Stimulation of the olfactory bulb (OB) determined if the OT neurons were olfactory-related. Ipsilateral VTA stimulation produced a change in neuronal activity in 77% of the neurons tested, with 41% being inhibited, 24% excited, and 12% had mixed response. Contralateral VTA stimulation produced changes in only 38%. Intravenous administration of haloperidol was used in examination of the role of dopamine in this neural connection. The results suggest that the VTA-induced inhibitory response on OT neurons is mediated by dopamine, whereas excitatory responses are not. The VTA inhibitory influence projects primarily to olfactory-related neurons, since 60% of olfactory-related OT neurons were inhibited--as compared to 34% of non-olfactory-related neurons. This study documents electrophysiologically the VTA-OT connection and suggests that the dopaminergic input may modulate olfactory information projected to the OT from the OB. It also supports the concept that the OT acts as an integration center in central olfactory processing.

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PubMed1986

Glucagon-related peptides in the rat hypothalamus.

Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism.

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PubMed1986

Effects of sleep-promoting substance on rat hypothalamic neuron activity.

The effects of electrophoretically applied sleep-promoting substance (SPS) on neuronal activity of the preoptic area (POA) and SPS interactions with some neurotransmitters were examined in the rat. In the POA, 14% of the tested neurons were excited and 13% were inhibited by SPS. Neurons that were excited by SPS were also excited by glutamate (Glu). The excitatory effect of Glu was blocked or attenuated by concurrent application of SPS in 35% of the neurons, and this modulatory effect was long-lasting. A significant number of SPS responsive neurons were inhibited by noradrenaline (NA). This inhibitory effect was attenuated, blocked or reversed by concurrent application of SPS in 28% of the tested neurons. There was no relation between the effects of acetylcholine (ACh) alone and those of SPS alone. The effects of ACh were modified by concurrent SPS application in 21% of the neurons tested; the effect was either enhancement or blockade of the ACh excitation. Possible contribution of SPS in the hypothalamus to the regulation of sleep and wakefulness is discussed.

Acetylcholine↗

PubMed1986

Central action of glucagon in rat hypothalamus.

The effects of electrophoretically applied glucagon on neuronal activity in the rat lateral hypothalamic area (LHA), dorsomedial hypothalamic nucleus (DMH), and ventromedial hypothalamic nucleus (VMH) were examined. In the LHA glucagon significantly suppressed the activity of glucose-sensitive neurons compared with its effect on non-glucose-sensitive neurons. This inhibitory effect of glucagon on LHA neurons was blocked by ouabain. Intracellular recordings from LHA neurons revealed that glucagon hyperpolarized the cell membrane without a significant change in the input membrane resistance. Intra-arterial injection of glucagon suppressed the activity of some neurons that were suppressed by electrophoretically applied glucagon. Similarly, glucagon suppressed the activity of significant numbers of DMH and VMH neurons with doses higher than those that affected LHA glucose-sensitive neurons. Cortical neurons were unaffected by glucagon. The data suggest that blood-borne glucagon could suppress the activity of LHA glucose-sensitive neurons and, in addition, might contribute to the control of metabolism and the termination of feeding behavior.

Animals↗

PubMed1986

Olfactory evoked potentials in the rat.

Routine clinical assessment of the integrity of the olfactory pathway using olfactory evoked potentials remains an elusive goal. One important difficulty arises from the uncertainty of the exact origin of the potentials: are they produced by olfactory or trigeminal elements? To resolve this problem, an animal model using the rat was developed. Amylacetate was used as an odorant stimulus, and potentials were measured and computer averaged after elimination of trigeminal and vomeronasal activity. A positive-negative wave was recorded from the olfactory bulb surface, and a negative wave often followed by a positive wave was recorded from the surface of the cerebral cortex. Measurements from the scalp surface gave comparable results. Lesioning experiments of the olfactory pathway indicate that the evoked potentials recorded at the vertex originate in the ventral forebrain, specifically in the prepyriform cortex, olfactory tubercle, and anterior olfactory nucleus.

Animals↗

PubMed1986

Effects of prostaglandin D2 on the activity of hypothalamic neurons in the rat.

The effects of electrophoretically applied prostaglandin D2 (PGD2) on neuronal activity in the rat lateral preoptic area (LPOA) and posterior hypothalamic area (PHA) were examined. In the LPOA, 20% of the tested neurons were excited, 26% inhibited, and 6% showed bidirectional response. The direct effects often showed desensitization after repeated applications. Neurons excited by PGD2 were significantly sensitive (excitation) to acetylcholine (ACh). The ACh excitatory effect was sometimes (38%) attenuated, blocked, or reversed by concurrent PGD2 application. Excitatory or inhibitory effect of noradrenaline (NA) was not related to the effects of PGD2; however, modulation of the NA responses by PGD2 was common (58%). Inhibition, the predominant NA response, was changed to no effect or to excitation during simultaneous PGD2 application. Changes of the NA responses from inhibition to excitation, or from excitation to inhibition-excitation sequences were observed after PGD2 infusion into the third cerebral ventricle at low concentrations. In 43% of the cells, neurotransmission in the LPOA following ventral noradrenergic bundle stimulation was modified by PGD2 application. PGD2 application tended to reduce the duration of inhibition and to extend that of excitation. The direct effects of PGD2 in the PHA were similar to those in the LPOA. Desensitization was also observed in the PHA, but no interrelations were observed among the effects of PGD2, ACh, and NA. Modulation of ACh and NA responses by PGD2 was rarely seen in the PHA. Possible contributions of PGD2 to sleep and thermoregulation are discussed.

Acetylcholine↗

PubMed1985

Effects of mazindol on rat lateral hypothalamic neurons.

In order to elucidate the mechanism of action of the anorectic drug, mazindol, effects of electrophoretically applied mazindol were examined on glucose-sensitive and non glucose-sensitive neurons in the rat lateral hypothalamic area (LHA), which is functionally important in food intake control. Mazindol was found to significantly suppress the firing rate of glucose-sensitive neurons. Ouabain a Na-K pump inhibitor, attenuated mazindol induced suppression of neuronal firing rate. Intracellular recordings revealed hyperpolarization of the membrane with no change in membrane conductance by perfusion of brain slice with 0.1 mM mazindol in bath. This was similar to the effect of 30 mM glucose. Results suggest that the inhibitory action of mazindol is mediated by activation of the Na-K pump. Spiroperidol, a dopamine antagonist, did not affect the inhibitory response to mazindol, suggesting direct action of mazindol on LHA neurons, independent of dopamine.

Animals↗

PubMed1984

Behavioral significance of monkey hypothalamic glucose-sensitive neurons.

Feeding-related neuronal activity of lateral hypothalamic glucose-sensitive and glucose-insensitive neurons was investigated in behaving monkeys. The behavioral paradigm was a high fixed ratio of bar pressing for food reward signaled by light and tone cues. Twenty-seven percent of the neurons tested were glucose-sensitive. The population of neurons which changed in firing rate during the feeding task was higher among glucose-sensitive cells than among glucose-insensitive cells. The activity of many glucose-sensitive neurons decreased during the bar pressing and reward periods. A small population of glucose-sensitive neurons responded to cue stimuli. The results suggest that glucose-sensitive neurons are mainly involved in the drive and/or reward mechanism of feeding behavior, and that these cells may have specific roles in neural control of hunger-motivated food acquisition.

Animals↗

PubMed1984

Effect of intracerebroventricularly infused glucagon on feeding behavior.

Administration of pancreatic glucagon into 3rd cerebral ventricle of rats suppressed feeding with potency greater than 1000 times that of peripheral administration. A low dose of glucagon (5 ng) suppressed food intake mainly in short-term and slightly in long-term. A medium dose (25 ng) produced delayed feeding suppression. A high dose (100 ng) suppressed only short-term food intake. From this evidence, it is concluded that intracerebroventricular administration of physiological concentration of pancreatic glucagon suppresses short-term food intake through the hypothalamus. The possible mechanism of feeding suppression by glucagon is discussed.

Animals↗

PubMed1983

Influence of catecholamines on reward-related neuronal activity in monkey orbitofrontal cortex.

Reward-related neuronal activity and its regulation by catecholaminergic input were investigated in the orbitofrontal cortex of the behaving monkey by means of extracellular unit recording and microiontophoretic application of drugs. Neuronal activity was modulated by reward situations and catecholamines. The activity of a majority of the noradrenaline-sensitive cells decreased and of the dopamine sensitive cells increased during food acquisition behavior. The results suggest that catecholamines could be involved in reward-related neuronal activity in the monkey orbitofrontal cortex.

Animals↗

PubMedDate not supplied

Effect of stimulation of the horizontal limb of the diagonal band on rat olfactory bulb neuronal activity.

Reports suggest that patients with Alzheimer's disease have deficient olfactory sensitivity and disruption of the cholinergic pathways. Elucidation of the cholinergic system in the olfactory bulb is essential to the understanding of this disease for diagnostic and therapeutic advances. Possible cholinergic projection to the olfactory bulb was studied in rats with transected medial forebrain bundles by stimulating the horizontal limb of the diagonal band, which contains cholinergic perikarya. Electrical stimulation of the horizontal limb of the diagonal band evoked negative potentials in the granule cell layer. Neurons in the granule cell layer were excited, and those in the mitral cell layer and external plexiform cell layer showed inhibition, often followed by excitation. These responses were attenuated by the administration of the cholinergic blocker, atropine. The role of cholinergic projection to olfactory bulb neurons is discussed.

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