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H Kaba

Publications and source records attributed to H Kaba.

At least 19 recordsLinked to original sources
PubMed1992

Oestrogen infusions into the amygdala potentiate excitatory transmission from the accessory olfactory bulb to tuberoinfundibular arcuate neurones in the mouse.

We have previously shown that oestrogen increases the percentage of tuberoinfundibular (TI) arcuate neurones that respond to electrical stimulation of the accessory olfactory bulb (AOB). This study focuses on the amygdala as a possible site for the hormonal modulation of AOB input to TI arcuate neurones. Local infusions of 17 beta-oestradiol (30 pmol) into the amygdala of ovariectomized female mice significantly potentiated excitatory responses of TI arcuate neurones to AOB stimulation. This effect appeared rapidly (less than 10 min) after infusion. The inactive oestrogen isomer, 17 alpha-oestradiol, infused in the same manner, was without effect. These results suggest that oestrogen acts directly on amygdala neurones, thereby modulating olfactory information relayed along the vomeronasal pathway to TI arcuate neurones.

Amygdala↗
PubMed1992

Analysis of synaptic events in the mouse accessory olfactory bulb with current source-density techniques.

The accessory olfactory bulb of the mouse was studied by current source-density analysis of field potentials to determine the laminar and temporal distribution of synaptic currents evoked by electrical stimulation of the vomeronasal organ. The one-dimensional current source-density analysis revealed two major spatially and temporally distinct inward membrane currents (sinks): one in the glomerular layer and the other in the external plexiform layer. The glomerular layer sink preceded the external plexiform layer sink by a mean of 5.5 ms. Local infusions of the broad-spectrum excitatory amino acid antagonist, kynurenate, into the accessory olfactory bulb blocked the external plexiform layer sink without an obvious effect on the glomerular layer sink. The selective non-N-methyl-D-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione produced a dose-dependent blockade of the external plexiform layer sink, whereas the selective N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonovalerate was without effect. These results, taken together with the cytoarchitecture of the accessory olfactory bulb, suggest that the glomerular layer sink results mainly from synaptic excitation evoked in the glomerular dendritic branches of mitral cells by the vomeronasal afferent fibres and the external plexiform layer sink mainly from non-N-methyl-D-aspartate receptor-mediated synaptic excitation in the peripheral processes of granule cells via the mitral to granule cell dendrodendritic synapse.

2-Amino-5-phosphonovalerate↗
PubMed1992

Cholecystokinin: critical role in mediating olfactory influences on reproduction.

Our electrophysiological studies in female mice have demonstrated that electrical stimulation of the accessory olfactory bulb excites tuberoinfundibular dopaminergic arcuate neurons via the amygdala-stria terminalis route. This study shows that the medial preoptic area is identified as an additional relay for the excitatory transmission by examining the effectiveness of locally infused lignocaine anaesthetic in blocking the transmission and that of electrical stimulation in evoking a shorter latency response. Based on the known immunohistochemical findings, further attention is focused on a transmitter mediating synaptic transmission in the medial preoptic area. The cholecystokinin-B type receptor antagonist L-365,260 (0.3, 0.6, 0.9 pmol), but not the A type receptor antagonist L-364,718 (0.9 pmol), infused into the medial preoptic area, blocked the excitation of tuberoinfundibular arcuate neurons in a dose-dependent manner. Conversely, cholecystokinin octapeptide (0.6 pmol) increased firing activity in such neurons. The antagonizing effect of L-365,260 was reproduced in the context of the olfactory block to pregnancy: bilateral infusions of this drug into the medical preoptic area of recently mated females immediately before exposures to strange males' pheromones prevented them from inducing pregnancy block. These findings implicate cholecystokinin acting on cholecystokinin-B receptors in the medial preoptic area as a mediator of olfactory influences on reproductive physiology.

Animals↗
PubMed1992

Influence of the electrical stimulation of the hypothalamus on adrenocortical steroidogenesis in hypophysectomized rats.

The electrical stimulation of the ventromedial hypothalamus (VMH), lateral hypothalamic area (LHA), periventricular arcuate nucleus (ARC), and posterior hypothalamus (PHY), on 14C transfer rates from 14C-1-acetate into adrenocortical steroids in adrenal slices of hypophysectomized rats were investigated. The 14C transfer rates into corticosterone and cortisol were increased by the stimulation of the VMH, ARC, and PHY, but decreased by the stimulation of the LHA. From these results, it might be suggested that these hypothalamic structures were involved in the regulation of adrenocortical steroidogenesis without participation of the pituitary.

Acetates↗
PubMed1992

The role of limbic-hypothalamic systems in metabolic responses of phenylalanine to repeated cold exposures in rabbits.

In this study we examine the effects of lesions to limbic or hypothalamic structures on the metabolic responses of phenylalanine in liver slices prepared from rabbits exposed to cold stress (-20 degrees C) for 12 hours at a fixed time once a day. The results were as follows: 1. The 1st cold exposure (cold exposure on the 1st day) had marked and various effects on phenylalanine metabolism, and the metabolic responses of phenylalanine to cold exposure gradually decreased and then completely disappeared with repetitions of exposure in intact rabbits. 2. The metabolic patterns and responses of phenylalanine to the 1st cold exposure were altered by lesioning the periventricular arcuate nucleus (ARC), ventromedial hypothalamus (VMH), stria terminalis (ST) or dorsal fornix (FX). 3. The complete abolishment of the metabolic responses to cold exposure by its repetition was observed in rabbits with lesions in the ARC or VMH as well. 4. In contrast, metabolic responses of phenylalanine to cold exposure in rabbits with lesions in the ST or FX remained even after six exposures. These results suggest that the ARC, VMH, amygdala (AMYG)-ST system and dorsal hippocampus (HPC)-FX system played a role in the metabolic regulation of phenylalanine and in the metabolic responses of phenylalanine to the 1st cold exposure and that the AMYG-ST and HPC-FX systems, but not the ARC or VMH, participated in the process of the metabolic adaptation of phenylalanine to cold exposure.

Amygdala↗
PubMed1992

Influence of the electrical stimulation of the medial amygdala on adrenocortical sensitivity to adrenocorticotrophin in hypophysectomized rats.

The effects of electrical stimulation of medial amygdala on the adrenocortical sensitivity to adrenocorticotrophin (ACTH) were investigated in hypophysectomized rats. The intravenous injection of ACTH increased the rates of 14C transfer from 14C-l-acetate into corticosterone and cortisol in the adrenal slices of hypophysectomized rats. The electrical stimulation of the medial amygdala produced a further increase in the rates of 14C transfer from 14C-l-acetate into corticosterone and cortisol. From these results, it might be suggested that the medial amygdala was capable of enhancing the adrenocortical steroidogenesis in response to ACTH.

Acetates↗
PubMed1990

GABAergic mechanisms are involved in the control of tuberoinfundibular arcuate neurons by the accessory olfactory bulb.

In this study we examined electrophysiologically the involvement of the intrinsic GABAergic system of the accessory olfactory bulb (AOB) in controlling the activity of tuberoinfundibular (TI) arcuate neurons in anaesthetized female mice. Local infusions of the gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline into the AOB enhanced the spontaneous firing activity of TI arcuate neurons with excitatory inputs from the AOB. This finding reveals a neural mechanism responsible for the pregnancy blocking effect of this drug in freely behaving female mice and, taken together with the cytoarchitecture of the AOB, suggests that the reciprocal dendrodendritic interaction between mitral cells and GABAergic granule cells in the AOB is critical to control of AOB output to TI arcuate neurons as part of the final common pathway of the accessory olfactory system.

Animals↗
PubMed1990

Olfactory recognition: a simple memory system.

Mice have an olfactory (pheromone) recognition memory located at the first relay in the sensory system. It is acquired with one-trial learning, contingent upon norepinephrine activation at mating, and lasts for several weeks. The mechanism involves Hebbian (association-dependent) changes in synaptic efficacy at dendrodendritic synapses in the accessory olfactory bulb. As a result of this memory, males made familiar by mating are recognized by the females, thereby mitigating pregnancy block. Such a memory function is biologically important to the female, as it is required to sustain pregnancy in the presence of her stud male's odors.

Amygdala↗
PubMed1990

Neural mechanisms underlying the action of primer pheromones in mice.

Our electrophysiological experiments in female mice have provided evidence that electrical stimulation of the accessory olfactory bulb orthodromically excites a subpopulation of tuberoinfundibular arcuate neurons by way of the amygdala. The present study shows that half of such neurons are identified as dopaminergic by examining the effectiveness of infusing 6-hydroxydopamine and 5,7-dihydroxytryptamine locally into the median eminence in blocking their antidromic response. Further attention is focused on excitatory amino acid receptors within the amygdala and the amygdaloid pathway that mediate the accessory bulb-induced excitation of tuberoinfundibular arcuate neurons. The excitatory transmission was reversibly blocked by intra-amygdala infusion (3 nmol) of the excitatory amino acid antagonists kynurenic acid, D,L-2-amino-5-phosphonovalerate, gamma-D-glutamylaminomethylsulphonate and D,L-2-amino-4-phosphonobutyrate. Intra-amygdala infusions (3 nmol) of N-methyl-D-aspartate and kainate markedly enhanced the firing activity of tuberoinfundibular arcuate neurons with excitatory inputs from the accessory bulb, whereas similar infusions of quisqualate were without effect Intra-stria terminalis infusions of the local anaesthetic lignocaine completely abolished the excitatory transmission in all the cells tested. Furthermore, tuberoinfundibular arcuate neurons stimulated from the accessory bulb were also orthodromically stimulated from the stria terminalis with a shorter latency. These studies demonstrate that the projections of the accessory olfactory bulb activate excitatory amino acid receptors within the amygdala and subsequently the stria terminalis route, thereby causing excitation of tuberoinfundibular dopaminergic arcuate neurons. This functional pathway can account for the reproductive effects so far described as a consequence of vomeronasal chemoreception.

Amino Acids↗
PubMed1990

Influence of electrical stimulation of the hypothalamus on ovarian steroidogenesis in hypophysectomized and adrenalectomized rats.

The effects of electrical stimulation of the lateral hypothalamic area (LHA), periventricular arcuate nucleus (ARC) and ventromedial hypothalamic nucleus (VMH) on the rates of 14C transfer from 14C-1 acetate into ovarian steroids in ovarian slices of hypophysectomized and adrenalectomized (H-A) rats were investigated. The 14C transfer rates into estrogen and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OH-P) were decreased by LHA stimulation. The stimulation of the ARC and VMH increased the rates of 14C transfer into estrogen, progesterone and 20 alpha-OH-P. From these results, it might be suggested that these hypothalamic structures were involved in the regulation of ovarian steroidogenesis without participation of the pituitary and adrenal.

20-alpha-Dihydroprogesterone↗
PubMed1990

Influence of dorsal hippocampal stimulation and dorsal fornix lesions on hepatic glucose metabolism in rabbits.

We examined the effects of stimulation of the dorsal hippocampus and lesions of the dorsal fornix on glucose metabolism in liver slices of rabbits. Hippocampal stimulation decreased the 14C transfer rates from 14C-glucose into CO2, ketone bodies, cholesterol ester and free fatty acids, but increased the rates into triglyceride, phospholipids and glycogen. Fornix lesions had various effects on glucose metabolism, and the effects of hippocampal stimulation on glucose metabolism were abolished by fornix lesions. These observations support the hypothesis that the hippocampus is an integral part of the brain regulator system in the hepatic glucose metabolism.

Animals↗
PubMed1990

Influence of microinjection of insulin into the ventromedial hypothalamus on acetate metabolism in rumen epithelium of sheep.

Injections of 50 microU insulin into the ventromedial hypothalamic nuclei (VMH) in intact sheep decreased the rates of 14C transfer from 14C-1-acetate into CO2, glucose, ketone bodies, and increased the rates into triglyceride and phospholipids in rumen epithelium of sheep. Insulin injections into the parietal cortex of intact sheep or into the VMH of sheep with VMH lesions had no effect on the acetate metabolism in rumen epithelium as compared with the control groups which received saline injections into the same brain regions. These results support the view that the VMH serves as an integral part of an insulin-sensitive brain regulatory system in the acetate metabolism of rumen epithelium.

Acetates↗
PubMed1989

Neural basis of olfactory memory in the context of pregnancy block.

In mice, only strange male pheromones block pregnancy; pheromones of the familiar male with which the female has mated have the capacity to block pregnancy but are ineffective with the consort female. Hence, some form of recognition/memory to the stud male is formed at mating. By infusing lignocaine locally into the accessory olfactory bulb and second order olfactory synapses in the medial nucleus of the amygdala, this study localizes changes that occur in the accessory olfactory bulb at mating to be subsequently important in preventing the stud male's pheromones from blocking pregnancy. Further attention is focused on the dendrodendritic synapses between mitral and granule cells in the accessory olfactory bulb. Blockade of the GABA receptors (granule to mitral cell synapse) in the accessory bulb without mating, but in the presence of male pheromones, prevents any male from blocking pregnancy. Conversely inhibition of protein kinase C, a second messenger system activated by excitatory amino acids (mitral to granule cell synapse), in the accessory bulb during a 4-h period after mating permits all male pheromones including the stud's to activate pregnancy block. While blockade of protein kinase C activity during the critical exposure time for memory formation prevents memory formation, infusions of a protein synthesis inhibitor (anisomycin) are without effect. However, protein synthesis inhibition in the accessory olfactory bulb in the late phase of the critical exposure time (3-6 h after mating) does prevent memory formation. These studies show that changes in synaptic plasticity in the accessory olfactory bulb following mating are critical to recognition of the stud male's pheromones, hence preventing these from subsequently blocking pregnancy.

Amygdala↗
PubMed1989

Excitatory influence of the accessory olfactory bulb on tuberoinfundibular arcuate neurons of female mice and its modulation by oestrogen.

The role of the accessory olfactory bulb in conveying pheromonal information to tuberoinfundibular arcuate neurons was examined electrophysiologically in chloral hydrate-anaesthetized, oestrogen (0.5 micrograms in silastic capsules)-treated and untreated ovariectomized Balb/c female mice. Electrical stimulation of the accessory olfactory bulb orthodromically excited part of tuberoinfundibular neurons which were antidromically stimulated from the median eminence and histologically verified as being located within the arcuate nucleus. No inhibitions followed accessory bulb stimulation. The excitatory response to accessory bulb stimulation was reversibly blocked by the local anaesthetic lignocaine infused into the amygdala. The percentage of tuberoinfundibular arcuate neurons responding to accessory bulb stimulation was significantly higher in oestrogen-treated than in untreated animals. There was no difference between the two groups for the antidromic activation threshold, spontaneous firing rate, absolute refractory period or frequency of successful antidromic propagation into the soma of tuberoinfundibular arcuate neurons. In oestrogen-treated preparations, tuberoinfundibular arcuate neurons responsive and unresponsive to accessory bulb stimulation could be distinguished by the frequency of successful antidromic propagation into the soma. These studies demonstrate that olfactory relay neurons in the accessory olfactory bulb act to enhance the activity of a subpopulation of tuberoinfundibular arcuate neurons via the amygdala and that this neural transmission is modulated by oestrogen.

Action Potentials↗
PubMed1989

Influence of microinjection of glucagon into the amygdala on hepatic acetate metabolism in rabbits.

Glucagon was injected directly into the medial amygdala (AMYG) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 3 ng glucagon into the AMYG of intact rabbits increased the rates of 14C transfer from 14C-1-acetate into CO2, glucose, ketone bodies, cholesterol ester, free fatty acids and phospholipids but decreased those of 14C transfer into triglyceride. However, the glucagon injection into the AMYG of rabbits with lesions of stria terminals or into the parietal cortex of intact rabbits had no effects on the hepatic acetate metabolism. These observations support the hypothesis that the AMYG is a part of the glucagon-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1989

Influence of electrical stimulation of the limbic structure on adrenocortical steroidogenesis in hypophysectomized rats.

The effects of electrical stimulation of the medial amygdala (AMYG) and dorsal hippocampus (DHPC) on the rates of 14C transfer from 14C-1-acetate into adrenocortical steroids in adrenal slices of hypophysectomized rats were investigated. The 14C transfer rates into corticosterone were increased by stimulation of the AMYG and DHPC. The 14C transfer rates into cortisol were increased by the AMYG stimulation but were not altered by the DHPC stimulation. From these results, it might be suggested that these limbic structures were involved in the regulation of adrenocortical steroidogenesis without participation of the pituitary.

Adrenal Cortex Hormones↗
PubMed1988

The effect of microinfusions of drugs into the accessory olfactory bulb on the olfactory block to pregnancy.

Female mice which have mated and are subsequently exposed to the odour (pheromones) of a strange male undergo hormonal changes resulting in a block to their pregnancy. The fact that the stud male's odours can also block pregnancies, that is other than his own, implies the formation of a memory or some form of recognition process by the female for this male's pheromones at the time of mating. The purpose of this study was to evaluate the effect of microinfusions of drugs which interfere with neural transmission, into the accessory olfactory bulbs. This was carried out immediately after mating over a 4-h period during which the "memory" to the stud male's pheromones is formed. Infusions of the alpha-blocker, phentolamine, blocked the formation of the olfactory memory, while the GABA receptor blocker, bicuculline, itself blocked pregnancy, but was without effect on memory formation. Protein synthesis inhibition or calpain inactivation in the accessory bulb was without effect on memory formation at any of the doses used. These studies demonstrate that GABAergic transmitter blockade in the accessory olfactory bulb at the time of mating can prevent subsequent blastocyst implantation some 3 days later, while alpha-noradrenergic blockade can prevent the formation of an olfactory memory to the stud male.

Animals↗