Changes in metabolic activity of neurons in the anterior hypothalamus nuclei during hyperthermia, fever, and hypothermia

Differently directed changes in metabolic activity of anterior hypothalamic nuclei's neurons in rats during hyperthermia, fever, and hypothermia were revealed with histochemical methods. During hyperthermia, the activity of energy metabolism enzymes increased as well as RNA content in the neurons of supraoptic, paraventricular and median preoptic anterior hypothalamic nuclei. This is shown by an increase in the metabolic activity of neurons of these nuclei. Metabolic activity in neurons of median preoptic nuclei decreased and was not changed considerably in neurons of supraoptic and paraventricular nuclei during endotoxin-induced fever. The development of hypothermia was characterised by a decrease in metabolic activity of neurons of supraoptic, paraventricular and medium preoptic nuclei. It is supposed that differently directed metabolic activity changes in neurons of anterior hypothalamic nuclei during hyperthermia are connected with the mechanisms of body temperature regulation (median preoptic nuclei) and neurosecretory processes (supraoptic and paraventricular nuclei).     

Role of Catecholamines in Regulation of the Functional State of Vasopressinergic Cells of the Rat Hypothalamus

In in vivo and in vitro experiments there have been shown different mechanisms of regulation of hypothalamic vasopressinergic neurons, including regulation due to changes of activity level of brain catecholaminergic and NPY-ergic neurons innervating hypothalamic vasopressinergic cells. We demonstrated in in vitro experiments that dopamine and noradrenaline had no effects on vasopressin expression, but inhibited its release from cell perikarya in supraoptic and paraventricular nuclei of hypothalamus. Besides, activity of vasopressinergic neurons might probably be regulated via activation of synthesis of these neurotransmitters in vasopressinergic cells themselves in the supraoptic and paraventricular nuclei. To activate synthesis of various neurotransmitters, in our case, catecholamines and NPY, in vasopressinergic neurons, different stimuli adequate to trigger or activate synthesis of these substances are required. Synthesis of catecholamines in vasopressinergic cells of supraoptic and paraventricular nuclei was revealed after immobilization stress and adrenalectomy. NPY is synthesized in neurons of hypothalamic neurosecretory centers in norm, and its synthesis increases at disturbances of NPY-ergic innervation of vasopressinergic cells.     

Topography of cholinergic neurons in the brain stem of the human fetus

Cholinacetyltransferase (ChAT) activity has been studied in 56 nuclei of the cerebral trunk in human fetuses at the age of 6-8 lunar months. Cytoplasmic and synaptic ChAT activity has been revealed and three types of neurons for cholinergic synaptic transmission has been distinguished. There are only cholinergic-noncholinoceptive neurons in five macrocellular nuclei of the cranial nerves. In 25 nuclei (paravicellular, reticular, pigmented, sensitive nuclei of the cranial nerves, nuclei of the funiculi posterior and some other switching centres) there are only noncholinergic-cholinoceptive neural cells. In 16 nuclei there are three, and in 8 nuclei--two types of cells. Either noncholinergic-cholinoceptive or cholinergic-noncholinoceptive cells predominate; there is no predominance of cholinergic-cholinoceptive neurons in any of the nuclei. Mapping on the position of the cholinergic synaptic transmission neurons in the cerebral trunk is composed.     

Properties of monosynaptic connections between callosal neurons and specific thalamic nuclei

A comparative analysis of monosynaptic afferent and efferent connections of callosal neurons and target neurons of transcallosal fibers with neurons of the specific ipsilateral thalamic nuclei (ventral posterolateral, ventral posteromedial, ventral lateral, and anteroventral) was undertaken on the sensomotor cortex of unanesthetized rabbits, using an electrophysiological method. Differences were demonstrated between callosal neurons and target neurons of transcallosal fibers with respect to monosynaptic inputs from the thalamic nuclei and pathways proceeding toward these structures and (or) entering the pyramidal tract. Among target neurons, compared with callosal neurons, more cells had descending projections (54 and 14%, respectively). Monosynaptic action potentials arose in 22% of target neurons in response to stimulation of specific thalamic nuclei, whereas no such responses occurred in callosal neurons. Projections of target neurons into thalamic nuclei were shown to be formed both by independent fibers and by axon collaterals of the pyramidal tract. It is postulated that the distinctive properties thus discovered indicate significantly greater convergence of influence of thalamic relay neurons on the target neurons; this determines differences known to exist in characteristics of receptive fields and spontaneous and evoked activity of callosal neurons, on the one hand, and of neurons excited synaptically by transcallosal stimulation, on the other hand.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 305–314, May–June, 1985.     

Response of recticular and dorsal thalamic nuclei neurons during extinction of conditioned implementation in the cat

Unit activity in 66 neurons of the reticular (R) nucleus and 31 neurons of the ventropostrolateral nuclei of the thalamus, and 14 neurons of the posterolateral nuclear complex, the pulvinar, were studied during extinction of the conditioned food implementation reflex. The number of R neurons that had responded to initial excitation in the first 300 msec after the conditional stimulus (CS) decreased with the extinction. Simultaneous disappearance of conditioned-reflex placement movements and late excitatory and inhibitory responses of R and dorsal thalamic nuclei neurons with latent periods exceeding 300 msec was also observed. Extinction of the conditioned reflex (CR) led to a significant lowering of background activity in two-thirds of investigated R and other thalamic nuclear neurons. This suggests that efferent effects from the reticular nucleus are decreased during Cr extinction.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 3–8, January–February, 1991.     

Cytophotometric study of the DNA concentration in the supraoptic neurosecretory nuclei of the hypothalamus

DNA content and distribution in supraoptic neuronal nuclei and in their satellites was studied in human subjects died under different conditions of hypothalamo-hypo-physeal neurosecretory activity: moderate (control) and high. In control observations, prevalence of diploid and paradiploid nuclei both in the secretory neurons and in the nuclei of glial satellites was noted. High neurosecretory activity was connected with a tendency towards increased DNA content in the neuronal nuclei, up to the appearance of some tetraploid elements. In the glial nuclei of the satellites, events of poliploidization were observed, that is, evidently, of adaptive character to maintain active functioning of the neurons under certain intensified conditions.     

Structural and functional organization of the dorsal column nuclei after unilateral exclusion of the medial lemniscus

The authors studied ultrastructural changes in neurons and alterations in evoked electrical responses after stimulation of the forelegs in the nuclei gracilis and cuneatus one year after unilateral section of the medial lemniscus in cats. It was shown that intact projectional elements of the nuclei gracilis and cuneatus had the normal cytological appearance and functional activity of their synaptical organization in spite of the cytoarchitectonic asymmetry. After disruption of the medial lemniscus the symmetrical nuclei of the dorsal columns did not exhibit any asymmetry in the distribution of evoked responses after stimulation of the forelegs.     

Quantitative comparison of the hominoid thalamus. I. Specific sensory relay nuclei.

Studies to date have indicated few differences in sensory perception among hominoids. Sensory relay nuclei in the dorsal thalamus--portions of the medial and lateral geniculate bodies (MGBp, LGBd) and the ventrobasal complex (VB)--in two gibbons, one gorilla, one chimpanzee and three humans were examined for anatomical similarity by measuring and estimating the nuclear volumes, neuronal densities, numbers of neurons per nucleus, and volumes of neuronal perikarya. The absolute volumes of these nuclei were larger in the larger brains; however, with the volume of the dorsal thalamus as a standard, these sensory relay nuclei showed negative allometry. The gibbons had about half as many neurons as did the other hominoids. Although the human VB had slightly more neurons, the numbers of neurons in LGBd and MGBp did not significantly differ between the great apes and humans. The volumetric distribution of the neuronal perikarya were similar among these hominoids. Other thalamic nuclei had much more diverse numbers of neurons and relative frequencies of their neuronal perikarya. The sensory relay nuclei appear to be a group of conservative nuclei in the forebrain. These results suggest that as a neurological base for complex behaviors evolved in hominids, not all parts of the brain changed equally.     

Localization of choline acetyltransferase in human brain stem neurons

Berth's method was used to study the cytochemical activity of choline acetyltransferase in truncus cerebri neurons of 6-8 lunar month-old human fetuses. Three types on neurons were diagnosed in the nuclei of the truncus cerebri with regard to cholinacetyltransferase localization: (1) cholinergic cholinoceptive neurons; (2) cholinergic non-cholinoceptive neurons; (3) non-cholinergic cholinoceptive neurons. The distribution of the neurons in 27 nuclei of the truncus cerebri is described.     

Cytologie du lobe anterieur de l'hypophyse du chien

Summary Detailed histochemical studies have been made on the distribution of various enzymes such as phosphatases, cholinesterases, glycolytic enzymes and respiratory enzymes in various components of the hypothalamus with special reference to the supraoptic and paraventricular nuclei of the Squirrel Monkey. Cytological studies have also been made by the McManus, Einarson, Gomori and Bargmann methods.A few neurons of these nuclei showed scanty Gomori-positive material in the cytoplasm for the Gomori and Bargmann methods. Nissl granules were located in the peripheral cytoplasm of most neurons. No glycogen granules were observed in these neurons. For these reasons, the Squirrel Monkey, like the rat, may not be a suitable species for the study of neurosecretory phenomena.The axons of these neurons were negative for the specific cholinesterase test, though the perikaryon and some parts of the processes gave a moderately positive reaction. These neurons may be non-cholinergic and the cholinergic fibers from an unknown nucleus may end in synapses on their cell bodies. Blood vessels and glial cells in the neurosecretory nuclei showed non-specific cholinesterase activity. This enzyme may hydrolyze the acetylcholine which has escaped splitting by specific cholinesterase. Alkaline phosphatase and acid phosphatase in these neurons may be involved in the metabolism concerned with the production of neurosecretory material. The neurons may be physicochemical receptors and may get enough energy and raw material to synthesize the neurosecretory material from the rich blood supply. Neurons of the supraoptic and paraventricular nuclei as well as other hypothalamic neurons, like neurons of other regions of the brain, are well equipped with the enzymes of the glycolytic pathways and the tricarboxylic acid cycle. Since the glial cells of these nuclei have amylophosphorylase activity and glycolytic pathways, they may work as energy donators to the neurons of the neurosecretory nuclei. T. R. Shanthaveerappa in previous publications.     

Regulation of orexin neurons by the monoaminergic and cholinergic systems

Orexins are a pair of neuropeptides implicated in energy homeostasis and arousal. Here we characterize the electrophysiological properties of orexin neurons using slice preparations from transgenic mice in which orexin neurons specifically express green fluorescent protein. Orexin neurons showed high frequency firing with little adaptation by injecting a positive current. The hyperpolarization-activated current was observed in orexin neurons by a negative current injection. The neurotransmitters, which were implicated in sleep/wake regulation, affected the activity of orexin neurons; noradrenaline and serotonin hyperpolarized, while carbachol depolarized orexin neurons in either the presence or absence of tetrodotoxin. It has been reported that orexins directly or indirectly activate the nuclei that are the origin of the neurons containing these neurotransmitters. Our data suggest that orexin neurons have reciprocal neural circuitries between these nuclei for either a positive or negative feedback loop and orchestrate the activity of these neurons to regulate the vigilance states.     

Age-related changes in nitroxidergic neurons in some nuclei of rat medulla oblongata

The paper presents a comparative study of NO neurons in the solitary tract nucleus, giant-cell, and lateral reticular nuclei in rats at 4, 7, 10, 14, 30, 45, and 60 days old and 3, 6, 12, 18, 24 months old. We determine the active quantitative and qualitative changes that occur in NO-positive neurons in the studied nuclei during the course of postnatal development. A low level of enzyme activity is observed on the first day; it reaches a peak level around the first-third month, then slowly declines. The size and number of nitroxidergic neurons increases, while the relative cell density decreases until the third month of life. We reveal local differences in the ontogenetic development of NO neurons in the studied nuclei. Solitary tract neurons have the highest rate of development, while NO neurons of old animals undergo early and extreme changes as compared to other studied nuclei of rat medulla oblongata.     

Possible mechanisms of involvement of the subthalamic nucleus and structures interconnected with this nucleus in movement disorders evoked by dopamine depletion

A possible mechanism of involvement of the subthalamic nucleus (STN) in movement disorders evoked by dopamine deficit is suggested. Multifunctional role of the STN is based on following reasons. Various STN cells participate in the cortico-basal ganglia-thalamocortical loop and in the basal ganglia-pedunculopontine-basal ganglia loop. Complexity of neural circuits is determined by functional heterogeneity of neurons in the nuclei, reciprocally connected with the STN, as well as by opposite modulation of activity of these neurons by dopamine due to activation of different types of pre- and postsynaptic receptors. Dopamine influences activity of STN neurons directly, through pre- and postsynaptic receptors. It is assumed that high-frequency stimulation of the STN can reduce or eliminate Parkinsonian symptoms not only owing to inhibition of activity of GABAergic neurons in the output basal ganglia nuclei, projected into the thalamus or pedunculopontine nucleus, but also due to excitation of glutamatergic or cholinergic neurons in the output nuclei, and due to potentiation of excitatory inputs to preserved dopaminergic neurons and subsequent rise in dopamine concentration.     

Histochemical distribution of alkaline and acid phosphatase and adenosine triphosphatase in the brain of squirrel monkey (Saimiri sciureus)

Summary The distribution of some phosphatases (alkaline and acid phosphatase and ATPase) have been studied on 15 thick fresh frozen serial sections in the various regions and nuclei of the squirrel monkey brain. The alkaline phosphatase activity is concentrated in the blood vessels and the peripheral part of the neurons of some nuclei (e.g., nucleus supraoptic hypothalami) and the lining cells of choroid plexus. Acid phosphatase (AC) is a cellular enzyme and is concentrated in the large neurons of nuclei basalis Meynert, diagonalis band of Broca, magnocellular hypothalamic nuclei, corpus mammillaris, large sized neurons of the thalamus (e.g., nuclei paracentralis, ventralis lateralis, ventralis posterior thalami, magnocellular part of corpus geniculatum laterale), motor neurons of cranial nerve nuclei, large neurons of the reticular formation, giant pyramidal cells of cerebral cortex and the Purkinje cells of cerebellar cortex. The AC activity does not show as much variation in the different areas of the brain as the oxidative enzymes, which may mean that AC is more related to static maintenance metabolism of cells than to dynamic functional metabolism. The ATPase activity is more pronounced in the neuropil and the blood vessels compared to the neurons. In the perikarya, ATPase is concentrated close to the cell membrane, which may be significant in molecular transport across the membrane as well as in impulse conduction and synaptic transmission. Significant ATPase activity has been observed in the nucleus caudatus and putamen, magnocellular hypothalamic nuclei, nuclei parataenialis, paraventricularis, paracentralis, ventralis anterior thalami, habenular complex and cranial nerve nuclei.This work has been carried out with the aid of Grant No. 00165 from The Animal Resources Branch, National Institute of Health and a grant (NGR-11-001-016) from The National Aeronautics and Space Administration. Thanks are due to Mrs. M. J. Nimnicht and Miss M. E. Rogero for their technical help.     

The Effects of Kainic Acid Injections on Guanylate Cyclase Activity in the Rat Caudatoputamen, Nucleus Accumbens and Septum

The activity of soluble and particulate guanylate cyclase (EC 4.6.1.2) has been compared with the distribution of neurotransmitter candidates in three rat forebrain nuclei, and the effects of local kainic acid injections into these nuclei have been tested. Soluble guanylate cyclase was highly concentrated in both the caudatoputamen and the nucleus accumbens, with lower activity found in the septum. This distribution coincided with markers for acetylcholine and monoamines, but not with markers for γ-aminobutyrate (GABA) or glutamate neurons. In contrast, particulate guanylate cyclase was equally active in all regions. Local injections of kainic acid, which destroyed cholinergic and GABA neurons in the caudatoputamen and in the nucleus accumbens, caused a rapid (70–90%) decrease in the soluble guanylate cyclase and a slower 50-60% fall in the particulate guanylate cyclase in these nuclei. In the septum, where kainate destroyed GABA cells but not cholinergic neurons, the guanylate cyclase activity was unchanged after the lesion. Thus, both the soluble and particulate guanylate cyclases appear to be concentrated in local neurons in the caudatoputamen and nucleus accumbens. In the septum, however, most of the guanylate cyclase activity is located outside kainate-sensitive neurons.     

Histochemically demonstrable esterase activity in the hypothalamus of the developing rat

Summary The distribution of the acetylcholinesterase, non-specific cholinesterase and non-specific esterase activity has been investigated histochemically in the hypothalamic neurons during the ontogenic development of the rat.Acetylcholinesterase activity is located in the supra-optic and para-ventricular nuclei mostly, but some activity is present in the other nuclei and in the median eminence of the adult rat, as well. The supra-chiasmatic neurons are always negative. The activity of non-specific cholinesterase was encountered in the endothelial cells of the capillaries, in the glia and in the ependymal cells especially around the supra-optic and para-ventricular neurons. The localization of the non-specific esterase was similar to that of the non-specific cholinesterase, but in addition activity is seen in the supra-optic and para-ventricular perikarya, in the parvo-cellular neurons of the tuberal area and in the median eminence. No sexual differences were seen in the distribution of the estrase activity.The appearance of acetylcholinesterase took place already before birth. At about the 16th post-coital day the area from which the arcuate and ventro-medial nuclei will differentiate was positive for acetylcholinesterase. A strong activity in these nuclei was observed during the critical period of the sexual differentiation of the rat hypothalamus (0–10 postnatal days). In the development of the non-specific cholinesterase and esterase no similar variation was seen. Acetylcholinesterase and non-specific esterase were seen in the neurosecretory nuclei before birth, non specific cholinesterase after birth, and non-specific esterase in the parvo-cellular neurons during the first post-natal week.Supported by a grant from The Finnish Medical Society Duodecim.     

Impact of Swimming Exercise Training on the Effects of Modulation of Mitochondrial Permeability Transition and NOS-1 Activation in Medullary Cardiovascular Neurons of Rats

Physical inactivity can be considered one of the major risk factors related to cardiovascular diseases. There are reasons to believe that the positive effect of exercise training is, to a large extent, mediated by modulation of the nervous control of the circulation system. In our previous studies, we showed that modulation of mitochondrial permeability transition in medullary cardiovascular neurons significantly contributes to the hemodynamic reactions in both the norm and a number of pathological states. In this study, we examined in acute experiments on urethane-anesthetized rats the hemodynamic effects mediated by either modulation of mitochondrial permeability transition in medullary neurons, or activation of neuronal NO synthase (NOS-1) in these neuronal populations after preliminary moderate exercise training (everyday swimming sessions of increased duration carried out for four weeks). It was shown that, after exercise training had been completed, the effects of injections of an inductor of mitochondrial permeability transition pore (MPTP) opening, phenylarsine oxide (PAO, 0.5 to 1.5 nmol), into populations of cardiovascular neurons in the medullary autonomic nuclei (nucl. tractus solitarius and paramedian and lateral reticular nuclei) were less expressed, as compared with those in control (untrained) animals. The data obtained suggest that exercise training can exert a protective action on functional activity of medullary neurons due to the decreased sensitivity of MPTPs to their opening. Injections of an inhibitor of MPTP opening, melatonin (0.7 to 2.1 nmol), into populations of medullary neurons under study in trained rats induced a decrease in the systemic arterial pressure (SAP), in contrast to untrained animals demonstrating mostly hypertensive responses following injections of melatonin into the above nuclei. Injections of an activator of neuronal NO synthase (NOS-1), L-arginine, into the medullary nuclei of swimming-trained rats resulted in more expressed hemodynamic shifts than in control animals, which suggests an increase in the activity of neuronal NO synthase in medullary neurons of such animals.