Local blood flow in the dorsal hippocampus and cerebellar cortex in the offspring of iodine-deficient rats

Experimental studies demonstrated that hypothyroidism can lead to depressive behavior and that thyroid hormones can have antidepressant effects. Postnatal changes in local blood flow in the dorsal hippocampus and cerebellar cortex were studied in the offspring of rats kept in conditions of iodine deficiency at conception and throughout gestation. The data obtained from these studies showed that severe limitation of iodine intake before and during gestation leads to marked deficiency in the blood supply to both of these brain structures, though the decrease in local blood flow in the dorsal hippocampus was more marked. Addition of iodine to the diet of females prevented this deficit of blood flow in both structures. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 92, No. 3, pp. 292–298, March, 2006.     

DC-potential shifts and regional cerebral blood flow reveal frontal cortex involvement in human visuomotor learning

Summary In the present study, two different physiological parameters were measured to describe brain activity related to visuomotor learning: performance-related DC-potential shifts and regional cerebral blood flow (rCBF) by Tc-99m HMPAO brain SPECT (Single Photon Emission Computerized Tomography). Visuomotor learning was required in a conflicting situation: a visual target moved on a screen and had to be tracked by moving the right hand in an inverted fashion (IT), e.g. movements of the target to the right side required hand movement to the left and vice versa. Compared to a normal, non-inverted control task (T), IT required the development of a novel motor program and the prevention of returning to routine direct pursuit. These additional demands in IT caused a relative hyperperfusion in regions including the middle frontal gyri, frontomedial cortex (including the supplementary motor area, SMA), right basal ganglia (caudate-putamen) and left cerebellum. Correlations of rCBF values between the middle frontal gyrus and basal ganglia may indicate a functional relation between these two brain structures. Visuomotor performance was accompanied by slow negative DC-potential shifts. In frontal and to a lesser degree in central recordings, amplitudes of DC-negativity were larger in IT than they were in T. This additional frontal negativity covaried with the success of learning. Results substantiate, now using a dual approach, previous suggestions that the frontal lobe plays an important role in visuomotor learning.     

Regional blood flow in response to exercise in conscious dogs

Summary Regional blood flow was measured with the microsphere method in conscious dogs under resting conditions and during moderate exercise on the treadmill.With respect to total organ blood flow, exercise induced a marked increase in blood flow to the calf muscles and to the myocardium, and a significant decrease in the arterial blood supply to the liver. Slight changes in blood flow to the other organs under study (various skeletal muscles, skin, brain, kidneys, intestine) were not significant.Study of the blood flow distribution within the myocardium showed a slight decrease of the ratio of subendocardial to subepicardial blood flow in the left ventricular free wall in response to exercise, and within the brain there was a relative increase in the blood flow to the cerebellum.     

Local norepinephrine depletion and learning-related neuronal activity in cingulate cortex and anterior thalamus of rabbits

Summary Multi-unit neuronal activity was recorded in posterior cingulate cortex (area 29) and the anterior ventral (AV) thalamic nucleus during discriminative instrumental avoidance learning wherein a response (stepping in an activity wheel) to a 0.5-s tone (CS⁺) prevented a foot-shock 5 s after CS⁺ onset. Presentations of a different tone (CS^-) on 50% of the conditioning trials in an irregular sequence with the CS⁺ did not predict shock and thus required no response. Two groups of rabbits received intracranial micro-injections of 6-hydroxydopamine (6-OHDA) to locally deplete the NE in area 29 or the AV nucleus. Vehicle was injected in the non-depleted area in each group and a third group received vehicle injections in both areas. Dopamine neurons in subjects that received 6-OHDA were protected by pre-treatment with GBR-12909. Neuronal data were collected during two pre-training sessions in response to the tones only and when the tones and shock were presented unpaired. Thalamically depleted rabbits made more, and cortically depleted rabbits made fewer, avoidance responses than controls during the early stages of behavioral acquisition, and cortically depleted rabbits made fewer responses than controls and thalamically depleted rabbits during extinction testing administered after the completion of acquisition. One effect of NE depletion on neuronal activity was entirely local: elimination of neuronal sensitization effects (enhanced discharges elicited by tones during the unpaired tone-shock pre-training treatment relative to pre-training with tones only). Other neuronal effects of NE depletion were system-wide, i.e., they occurred whether the depletion was cortical or thalamic. These were: attenuation of area 29 tone-elicited neuronal discharges and enhancement of AV thalamic discharges before and during training; elimination in area 29 of neuronal discrimination between CS⁺ and CS^-, induced in controls by CS⁺-shock pairings in the first conditioning session; induction of this neuronal discrimination, not present in controls, in the AV nucleus during the first conditioning session; attenuation of discharge enhancements elicited in controls by unexpected stimuli (presentation of auditory stimuli different in quality and incidence from the CS⁺). Excepting the noted losses at the outset of training, the results did not support an involvement of NE in the production of cingulate cortical or AV thalamic excitatory and discriminative training-induced neuronal activity. The system-wide alterations due to NE depletion implicated NE in the processing of unexpected events and in the production of dynamic neuronal patterns relevant to mnemonic retrieval. Several of the depletion-related neuronal changes were similar to the effects of hippocampal formation (subicular) lesions, suggesting that NE-dependent functions in area 29 and the AV nucleus are governed by hippocampal efferents, which may control the release of NE in these areas.     

Effect of nonachlazine and oxyfedrine on the coronary blood flow in dogs

The coronary blood flow in anesthetized and unanesthetized dogs was measured by means of an ultrasonic Doppler radiotelemetric apparatus. The ultrasonic transducer was placed on the upper third of the descending branch of the left coronary artery. Nonachlazine was shown to increase the coronary blood flow considerably in both anesthetized and unanesthetized dogs. However, the action of the substance lasted only 2–3 min and depended on changes in cardiac activity. Oxyfedrine increased the coronary bllod flow by a lesser degree than nonachlazine but for a longer time (mean 20 min). Considering the high effectiveness of the two substances in clinical practice the authors conclude that the increase in the coronary blood flow is not the main course of action when attempting to obtain an antianginal effect in patients with ischemic heart disease.Laboratory of Pharmacology of the Cardiovascular System, Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 1, pp. 34–38, January, 1977.     

Local cerebral blood flow velocity in newborn rats in normocapnia and hypercapnia

The local cerebral blood flow (LCBF) in the caudate nucleus was investigated in experiments on unanesthetized newborn rats by determing the rate of hydrogen saturation of the brain tissue and the cerebral blood volume was studied by plethysmography. LCBF in newborn animals was found to be considerably lower than in adults. Inhalation of CO₂ by newborn, unlike by adult rats, did not cause an increase in LCBF and the cerebral blood volume also remained unchanged.Laboratory of Brain Development, Scientific-Research Institute of Pediatrics, Academy of Medical Sciences of the USSR. (Presented by Academician M. Ya. Studenikin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 139–141, August, 1977.     

Autoregulation of renal blood flow in the rat

Summary Renal blood flow was measured in rats anaesthetized with pentobarbital sodium by employing the PAH clearance method and the¹³³Xe washout technique. Both methods were in good agreement. In 17 rats a 25% decrement of blood pressure was attained through haemorrhage; RBF measured by PAH clearance declined by 3%, according to¹³³Xe washout by 2.7%. In further 21 rats an increase of blood pressure by an average of 265 was achieved by occlusion of the carotid arteries; RBF measured by PAH clearance declined by 3%, according to¹³³Xe washout by 1.1%. RBF was therefore almost perfectly autoregulated during both experimental manoeuvres; glomerular filtration rate (inulin clearance) was autoregulated in a similar manner. Water and sodium excretion changed in proportion to changes of blood pressure.with technical assistance of JANA HOLLYOVÁ     

Effects of bilateral carotid occlusion and auditory stimulation on renal blood flow and sympathetic nerve activity in the conscious dog

In conscious foxhounds with intact aortic baroreceptors the effects of common carotid occlusion (C. C. O.; 3 dogs) or excitement (elicited by a sudden loud noise due to firing a pistol; 7 dogs) on renal blood flow (R.B.F.) were studied. C.C.O. increased arterial blood pressure by 40–50 mm Hg and heart rate by 22 beats/min while R.B.F. remained unchanged. When kidney perfusion pressure was maintained during C.C.O. there was also no change in R.B.F. Excitement increased mean aortic blood pressure by 35 mm Hg and heart rate by 84 beats/min; R.B.F. was transiently reduced by 40% of control.In another 3 foxhounds successful recordings of renal sympathetic nerve activity (R.S.N.A.) were obtained in the conscious state for 2–7 postoperative days. The effects of C.C.O. or excitement — elicited by whistling or hand-clapping — on R.S.N.A. were tested. There was pulse-synchronous nerve activity in the resting conscious animal. C.C.O. induced a steady state increase of averaged R.S.N.A. by 62% of control. Excitement was associated with transient bursts of activation of averaged R.S.N.A. by 500% of control.It is concluded that total R.B.F. is not changed during the baroreceptor short-term adjustment of blood pressure although changes in sympathetic outflow to the kidney are observed under comparable conditions. In contrast, excitement causes a much higher degree of sympathetic activation; this is probably responsible for the intense, transient renal vasoconstriction.This study was supported by the German Research Foundation within the S.F.B. 90 Heidelberg     

The effects of L-carnitine on the combination of, inhalation anesthetic-induced developmental, neuronal apoptosis in the rat frontal cortex

The anesthetic gas nitrous oxide (N2O) and the volatile anesthetic isoflurane (ISO) are commonly used in surgical procedures for human infants and in veterinary and laboratory animal practice to produce loss of consciousness and analgesia. Recent reports indicate that exposure of the developing brain to general anesthetics that block N-methyl-D-aspartate (NMDA) glutamate receptors or potentiate GABA(A) receptors can trigger widespread apoptotic neurodegeneration. In the present study, the question arises whether a relatively low dose of ISO alone or its combination with N2O entails significant risk of inducing enhanced apoptosis. In addition, the role of L-carnitine to attenuate these effects was also examined. Postnatal day 7 (PND-7) rat pups were exposed to N2O (75%) or a low dose of ISO (0.55%) alone, or N2O plus ISO for 2, 4, 6 or 8 h with or without L-carnitine. The neurotoxic effects were evaluated 6 h after completion of anesthetic administration. No significant neurotoxic effects were observed for the animals exposed to N2O or ISO alone. However, enhanced apoptotic cell death was apparent when N2O was combined with ISO at exposure durations of 6 h or more. Co-administration of L-carnitine (300 or 500 mg/kg, i.p.) effectively protected neurons from the anesthetic-induced damage. These data indicate that 6 h or more of inhaled anesthetic exposure consisting of a combination of N2O and ISO results in enhanced neuronal apoptosis, and L-carnitine effectively blocks the neuronal apoptosis caused by inhalation anesthetics in the developing rat brain.     

Local cerebral blood flow in gently restrained rats: effects of propranolol and diazepam

Summary The cerebrovascular consequences of the gentle restraint commonly used for the measurement of local cerebral blood flow (LCBF) in conscious rats has been tested by using two drugs, propranolol and diazepam. Propranolol induced small LCBF decreases in 7 structures suggesting that the cerebral circulation was partially controlled by the activation of intra or extracerebral aminergic pathways in this protocol. Sedative doses of diazepam reduced LCBF in most of the structures but anxiolytic doses increased it in 4 structures. This effect may be due to a regionally differentiated modification of activity in the brain due to the selective inhibition of limbic structures by diazepam. Since propranolol and diazepam induced only small changes, the LCBF of gently restrained rats appeared to be minimally affected by the stressful situation imposed by the protocol.     

Correlation between cerebral blood volume and cerebral blood flow in the cat

Summary Blood flow and blood volume were measured simultaneously in the same cerebral region in anaesthetized cats with controlled respiration. The measurements were made with the same scintillation-detector, using the freely diffusible indicator ¹³³ Xenon for flow determinations and the intra-vascular indicator RISA (¹³¹I) for volume recordings. A very high correlation was found between volume and flow changes (r = .96, p < 0.001). This finding indicates that variations of regional cerebral blood volume are accompanied by proportional blood flow changes.Attaché de recherche au C.N.R.S., Laboratoire de Neurophysiologie, Hopital Henri Rouselle, Paris, France.     

Local cerebral blood flow in the rat during severe hypoglycemia,and in the recovery period following glucose injection

In order to assess the influence of severe hypoglycemia on local cerebral blood flow (1-CBF) artificially ventilated rats, maintained on 70% N₂O, were injected with insulin to provide either an EEG pattern of slow-wave poly spikes, or cessation of spontaneous EEG activity for 5, 15, or 30 min (“coma”). In other animals, glucose was injected at the end of a 30 min period of “coma” and 1-CBF was measured after recovery periods of 5, 30, 90, or 180 min. Local CBF was measured autoradiographically with ¹⁴C-iodoantipyrine as the diffusible tracer. In the slow-wave poly spike period 1-CBF was increased in most of the structures studied, and reached values that were 1.4 to 3.2 times greater than control. In many structures, cessation of EEG activity was accompanied by a further increase in 1-CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400–500% of control. The increase in 1-CBF was unrelated to arterial hypertension, hypercapnia, or hypoxia. 5 min after glucose injection the hyperemia persisted in only some of the structures studied; in others, the 1-CBF were close to, or below, control values. During the subsequent recovery period 1-CBF was markedly reduced with some structures (cerebral cortical areas, hippocampus, and caudate-putamen) showing flow rates of only 20–35% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed. The hypoperfusion was unrelated to arterial hypotension, hypocapnia, or increase in intracranial pressure. It is concluded that, like hypoxia and ischemia, substrate deficiency due to hypoglycemia is accompanied by vasodilatation in the brain. Furthermore, like long-lasting ischemia, severe hypoglycemia is followed by a delayed hypoperfusion syndrome that, by restricting oxygen supply, may well contribute to the final cell damage incurred.     

Splenic blood flow and intrasplenic flow distribution in rats

Summary In 75 rats, anesthetized with pentobarbital and breathing spontaneously, regional splenic blood flow (rSBF) was measured by means of the⁸⁵Kr(β)-clearance technique after an intraaortic slug injection of the dissolved indicator. In the normal and undisturbed spleen in situ rSBF is linearly related to the mean arterial blood pressure (MABP) within the range of 30–140 mm Hg. Mean rSBF is 0.71 ml/g/min, the mean arterial blood pressure being 105 mm Hg. In normal rats rSBF decreases significantly with increasing body weight or age. After total obstruction of the open circulation by application of rigid spherocytes, mean rSBF is reduced to 0.26 ml/g/min and is independent of the mean arterial blood pressure within the same range. In splenomegaly, due to enhanced reticuloendothelial activity and intensified immunological responses after tumor implantation, an increase in total splenic blood flow is found. However, related to 1 g of splenic wet weight, rSBF is diminished. In splenomegaly, rSBF also linearly depends on MABP within a wide range. Mean rSBF is 0.51 ml/g/min, the mean arterial blood pressure being 91 mm Hg. The distribution of intrasplenic blood flow between open and closed circulation depends on the size of the mean arterial blood pressure. The perfusion rate of the open circulation, compared with rSBF amounts to 72–93% (MABP=80–130 mm Hg).     

Interactions between inputs from adjacent digits in somatosensory thalamus and cortex of the raccoon

Interactions between somatosensory afferents arriving from different points in the periphery play an important role in sensory discrimination and also provide the substrate for plasticity following peripheral injury. To examine the extent and time course of such interactions, extracellular recordings were made from neurons in the primary somatosensory cortex and the ventroposterior lateral thalamus of anesthetized raccoons. Interactions between adjacent digits were studied using the conditioning-test paradigm in which a test pulse was delivered to the digit containing the neuron's receptive field (the on-focus digit) at various intervals following conditioning stimulation of an adjacent, off-focus digit. Off-focus stimulation produced predominantly inhibition of the test response with a maximum effect at 20–40 ms in both cortex and thalamus. The mean inhibition was approximately twice as large in the thalamus as in the cortex. Recordings were made in other animals after unmyelinated C fibers had been destroyed in the on-focus digit by subcutaneous injection of capsaicin. This resulted in a doubling of the responses evoked by the test stimulus in both regions, but the spontaneous discharge rate was not changed. The amount of inhibition produced in the cortex was unchanged by capsaicin treatment, but was reduced in the thalamus compared to control animals. This indicates that capsaicin-sensitive peripheral afferents provide a tonic control over interdigit inhibition in the thalamus.     

Changes of collateral perfusion pressure and segmental coronary resistances during reactive hyperemia in anesthetized dogs

Changes of collateral perfusion pressure (CPP) and segmental coronary resistances during reactive hyperemia were studied in nine chloralose-urethan-morphine anesthetized open-chest dogs. Coronary perfusion pressure was controlled by a cannula in the left main coronary artery and inflow measured by an electromagnetic flowmeter. The first or second diagonal branch of the left anterior descending coronary artery was cannulated and perfused from a carotid artery; inflow was abolished by embolization with latex microspheres (diameter: 25±5 ) and peripheral coronary pressure was assumed to represent CPP. Segmental coronary resistances were defined as follows: Proximal coronary resistance (R₁) was calculated from the difference between coronary perfusion pressure and CPP devided by coronary inflow. Distal coronary resistance (R₂) was calculated from CPP divided by coronary inflow. Reactive hyperemia was produced by interruption of coronary inflow for 15 s and analysed at 30 s and 60 s of reperfusion when cardiac function had recovered. At baseline, R₁ was 0.52±0.04 mm Hg x min ×100 g/ml (RU) and R₂ 0.63±0.07 RU. At 30 s, R₁ was reduced by 19±3% (P<0.01) this was less (P<0.05) than R₂ which was reduced by 32±3% (P<0.01). At 60 s R₁ and R₂ were reduced by 11±2% and 13±2%, respectively; this was not significantly different. Accordingly, CPP (baseline: 59±4 mm Hg) at 30 s was reduced by 7±2% (P<0.03), at 60 s the reduction was not significant. The data suggest that reactive hyperemia, as a model of metabolic coronary dilatation, may reduce CPP equivalent to a coronary steal phenomenon.     

No relation between atrial natriuresis and renal blood flow in conscious dogs

Summary Conscious dogs were used to study whether changes in total renal hemodynamics are responsible for diuresis and natriuresis during an experimental increase in left atrial pressure (LAP). To ensure a controlled dietary sodium intake, the dogs (n=8) were chronically kept on ahigh or alow sodium intake diet (HSI; LSI). After the dogs had completely recovered from surgery (carotid loop, thoracotomy, flank incision), LAP was increased by about 10 cm H₂O for 60 min by tightening a purse string around the mitral annulus (51 expts). Mean urine volume (V) increased in both groups to a comparable degree. Mean sodium excretion increased somewhat more in HSI dogs, but remained elevated in LSI dogs after the LAP increase. Renal blood flow (electromagnetic flow transducer) and inulin clearance did not change. Renal vascular resistance (RVR) increased by about 20% (HSI) and 15% (LSI). — When the induced LAP increase was terminated, V decreased. RVR decreased in HSI dogs by about –11% and in LSI dogs by about –6% below control values.—It is concluded that volume regulatory mechanisms induced by an experimental LAP increase operate independently of changes in total renal blood flow.The Arbeitsgruppe Experimentelle Anästhesie is member of the Research Group Autonomic Regulations Freie Universität Berlin     

EEG frequency content related to regional blood flow of cerebral cortex in cat

Summary The EEG frequency content in cats, anaesthetized by Nembutal and artificially ventilated, was altered by means of injections of either additional Nembutal or of Metrazol. The EEG in cerveau isolé preparations was also changed in the same way. The regional cortical blood flow was determined by means of the ⁸⁵Krypton technique. A high correlation was found between the frequency content of the EEG, measured by means of manual frequency analysis, and the regional cortical blood flow. The cortical blood flow increased when the mean frequency increased, and vice versa. A similar correlation was found when the EEG mean frequency was changed by means of sensory stimulation.On leave of absence from the University of Montpellier, France.This investigation was sponsored by the Swedish Medical Research Council (Project 21x-84-01 and 21x-84-02) and by the Wallenberg Foundation, Stockholm.     

Primary structural modules of the dorsal nuclei of the thalamus and motor cortex in humans

The aim of the present work was to study the primary structure of the modular organization of neurons in the dorsal nucleus of the thalamus (ventral anterior, ventral lateral, anterior ventral, anterior medial, anterior dorsal, medial, reticular) and motor cortex (fields 4 and 6) in humans by the Nissl, Kluver-Barrera, and Golgi silver nitrate impregnation methods. These studies showed that neurons in the dorsal nuclei of the thalamus and the motor cortex are organized as small groups and short chains fulfilling defined criteria. These neuronal complexes, forming individual structural units, were termed primary structural modules. Comparison of primary structural modules in the dorsal nuclei and motor cortex showed that the principles of organization were identical in both locations. Thus, the dorsal nuclei of the thalamus and motor cortex in humans show two principles of the organization of neurons into primary structural modules: the group and chain principles. __________ Translated from Morfologiya, Vol. 129, No. 1, pp. 24–29, January–February, 2006.     

Tissue PH2 measurement for continuous estimation of blood flow changes in rat kidney cortex and medulla

A method is described for estimation of local blood flow changes in the renal cortex and medulla, based on continuous polarographic measurement of tissue pressure of electrochemically generated hydrogen (PH₂). The technique was used in anaesthetized female Wistar rats. The changes in cortical PH₂ were negatively correlated with those in flow velocity in the renal artery (Doppler probe). To evaluate the method, PH₂ responses to a reduction of renal perfusion pressure (RPP) and to angiotensin II were examined. RPP reduction from 130 mmHg to 104 mmHg increased the cortical PH₂ by 3.5% and medullary PH₂ by 6.9% (difference significant at P<0.02). With RPP reduction from 113 mmHg to 76 mmHg the values were 6.9% and 11% respectively (difference significant at P<0.001). Angiotensin II infusion increased cortical PH₂ by 8.7% and medullary PH₂ by 4.1% (difference significant at P<0.005). It is concluded that the method enables continuous estimation of blood flow changes in the renal cortex and medulla.