Showing papers in "Acta Physiologica Scandinavica in 1965"

Evidence for the existence of monoamine neurons in the central nervous system. ii. experimentally induced changes in the intraneuronal amine levels of bulbospinal neuron systems.

Abstract: SummaryWith the help of the highly specific and sensitive fluorescence method of Falck and Hillarp together with the histochemical and pharmacological criteria for the specificity of the fluorescence reaction convincing evidence has been obtained that the fine, varicose nerve fibres observed in a vast number of regions in the mammalian central nervous system (mouse, hamster, rat, guineapig, rabbit, cat), which exhibit a green or yellow fluorescence, contain primary catecholamines and 5-HT respectively. Strong support has been given for the view that CA fibres showing a rapid recovery after administration of α-MMT contain DA, while those showing a slow recovery contain NA.There is little doubt that the monoamine-containing fibres in the brain represent the terminal ramifications of axons belonging to specific monoamine neurons and that they are true synaptic terminals. They seem to make their contacts via the varicosities which have extremely high concentrations of amines and in all probability represent the presynaptic structures, specialized for synthesis, storage and release of the amines. The central monoamine terminals thus have the same characteristic appearance as the adrenergic synaptic terminals in the peripheral nervous system.All the data strongly support the view that the specific central neurons giving rise to the terminals are monoaminergic, i.e. function by releasing their amines from the synaptic terminals. Consequently, DA, NA and 5-HT seem to be central neurotransmitters.Not only the median eminence but also the nuc. caudatus putamen, tuberculum olfactorium, nuc. accumbens and the small circumscribed areas medial to nuc. accumbens contain very fine (partly sublightmicroscopical) CA terminals. These areas react to treatment with reserpine, nialamide-dopa and α-MMT in the same way and since the nuc. caudatus putamen and tuberculum olfactorium are known to have a high DA content it seems likely that abundant DA terminals are accumulated in these special areas.

The metabolism of fatty acids in the rat. vi. arachidonic acid.

Abstract: Goransson, G. The metabolism of fatty acids in the rat. VI. Arachidonic acid. Acta physiol. scand. 1965. 64. 1–5. -H3-labeled arachidonic acid and C14-labeled palmitic acid were simultaneously injected into male rats. Arachidonic acid was preferentially incorporated into liver phospholipids as might be expected from the preponderance of this fatty acid in liver phospholipids as compared to glycerides. Initially, the labeled arachidonic acid and the labeled palmitic acid were oxidized at similar rates but at later times more arachidonic acid than palmitic acid was recovered from the whole animal. This may be explained by the preferential incorporation of arachidonic acid into phospholipid in combination with the low turnover rate of the phospholipids, especially those containing essential fatty acids. The pattern of label in the blood glycerides closely resembled that in the corresponding liver fraction.

The distribution of adrenergic nerve fibres to the blood vessels in skeletal muscle.

Abstract: Fuxe K and G Sedvall The distribution of adrenergic nerve fibres to the blood vessels in skeletal muscle Acta physiol scand 1965 64 75–86 The distribution and morphological construction of the adrenergic innervation to the various sections of the vascular bed in skeletal muscle of the cat were studied using a specific histochemical fluorescence technique A typical adrenergic ground plexus (Hillarp 1946, 1959) was seen directly superimposed on the smooth muscle layer of the vessels The nerve terminals seldom penetrated into this layer The arteries entering the muscles showed only a sparse amount of adrenergic fibres, whereas the intra-muscular arteries, arterioles and metarterioles exhibited a fairly rich supply The innervation was uniform, no definite accumulation of adrenergic fibres being observed in any section of the vascular bed The capillaries did not seem to receive any adrenergic fibres The vessels on the venous side had a very sparse innervation Single nerve bundles could be observed in relation to some small venules (20–40 μ) but only occasionally were adrenergic fibres seen around intramuscular veins with diameters above 50 μ Possible mechanisms for the mediation of nervous vasoconstrictor stimuli to the various vessel sections are discussed

The Limits of Firing Frequency in Cat Lumbosacral Motoneurones Possessing Different Time Course of Afterhyperpolarization

Abstract: Kernell, D. The limits of firing frequency in cat lumbosacral motoneurones possessing different time course of after hyperpolarization. Acta physiol. scand. 1965. 65, 87–100. — Long-lasting repetitive discharges were set up in cat lumbosacral motoneurones by steady currents injected through the tip of an intracellular micro-electrode. The upper and lower limits of discharge frequency of the various motoneurones were significantly correlated with the time course of their afterhyperpolarization the latter being measured from single spike discharges (generally antidromic). From previous work it is known that the relation between discharge frequency and current strength (the “f-I relation”) is linear over a certain range from the minimal firing rate and upwards (Granit, Kernell and Shortess 1963, Kernell 1965 b). In the present paper it was shown that the maximal discharge frequency within this linear part of the f-I relation was also significantly correlated with the time course of afterhyperpolarization. The findings are discussed with regard to problems of regulation of muscle tension by repetitive firing on the part of the motoneurones.

Effects of arterial carbon dioxide tension and oxygen saturation on cerebral blood flow autoregulation in dogs

Abstract: Effects of arterial carbon dioxide tension and oxygen saturation on cerebral blood flow autoregulation in dogs. Acta physiol. scand. 1965. 66. Suppl. 258. 27–53. - Pressure-flow relation- ships of the cerebral circulation under influence of variations in arterial carbon dioxide tension and oxygen saturation were studied in pentobarbital anaesthetized dogs. Cerebral blood flow was measured by recording of the γ- emission of radioactive krypton (Kr85), which was injected into the vertebral artery. The recorded desaturation curve was resolved into two exponential phases and the fast phase was considered as representative of blood flow in the grey matter of the brain. It was demonstrated that autoregulation of flow occurred within wide pressure limits under normo- and hypocapnia. Auto-regulation was less pronounced under hypercapnia and was abolished at low arterial oxygen saturation. Possible mechanisms of autoregulation of cerebral blood flow are discussed. Evidences are presented which speak against the theory that changes in the carbon dioxide tension are the main cause of this autoregulation. The results from previous studies concerning the principal effects of arterial carbon dioxide tension and oxygen saturation on cerebral blood flow were confirmed.

Identification and Cellular Localization of the Catecholamines in the Retina and the Choroid of the Rabbit

Abstract: Haggendal, J. and T. Malmfors. Identification and cellular localization of the catecholamines in the retina and the choroid of the rabbit. Acta physiol. scand. 1965. 64. 58–66. – By means of fluorescence microscopical and chemical methods the catecholamines of retinas and choroids were examined in rabbits normally, after treatment with drugs interfering with catecholamine storage, and after bilateral cervical sympathectomy. Dopamine was found to be the dominating catecholamine in the retina, 0.1–0.2 μg per g. It was localized to particular neurons. The results support the view that dopamine serves as the transmittor of these neurons. Noradrenaline was found in the choroid, 0.2–0.3 μg per g. It was localized to adrenergic vascular nerves.

The permeability of brain capillaries to non-electrolytes.

Abstract: Crone, C. The permeability of brain capillaries to non-electrolytes. Acta physiol. scand. 1965. 64. 407–417. – By means of the“Indicator diffusion” method blood-brain barrier permeability characteristics were studied on dogs. The permeability coefficient of fructose, glycerol, propylene glycol, urea, thiourea, antipyrine, ethanol, propanol and butanol was calculated. If these substances are ordered according to their rate of passage from blood into brain tissue a hierarchy is found which corresponds to that which is typical of the permeability of cell membranes to non-electrolytes. The experiments lend support to the view advanced by the late August Krogh that the permeability characteristics of the blood-brain barrier are analogous to those of cell membranes in general. This conclusion is discussed against the background of recent findings of morphologically-demonstrated tightness of cerebral capillaries which imply that material which diffuses from blood into brain tissue must pass the plasma membranes of the endothelial cells.

The Adaptation and the Relation between Discharge Frequency and Current Strength of Cat Lumbosacral Motoneurones Stimulated by Long‐Lasting Injected Currents

Abstract: Kernell, D. The adaptation and the relation between discharge frequency and current strength of cat lumbosacral motoneurones stimulated by long-lasting injected currents. Acta physiol. scand. 1965. 65. 65–73. — Cat lumbosacral motoneurones were stimulated by steady currents injected through the tip of an intracellular micro-electrode. The results strongly indicate that the majority of undamaged motoneurones are capable of responding to steady currents by long-lasting and well maintained repetitive discharges. Such discharges from various motoneurones were studied with regard to the adaptation and the slope of the linear relation between discharge frequency and current strength (cf. Granit, Kernell and Shortess 1963 a, b). Measurements were also made of the lowest current strength (in units of rheobase) which was needed for eliciting a steady repetitive discharge. None of these characteristics relating to repetitive firing were found to be correlated with the duration of afterhyperpolarization, the latter being measured by single spike discharges (generally antidromic). The results have been discussed also with reference to earlier findings concerning tonic and phasic repetitive firing of motoneurones stimulated by muscle stretch.

High-Frequency Repetitive Firing of Cat Lumbosacral Motoneurones Stimulated by Long-Lasting Injected Currents

Abstract: Kernell, D. High-frequency repetitive firing of cat lumbosacral motoneurones stimulated by long-lasting injected currents. Acta physiol. scand. 1965. 65. 74–86. Repetitive discharges were initiated in motoneurones by steady currents injected through an intracellular micro-electrode. At weaker currents, producing firing rates up to on the average 51 (30–84) imp/sec, the steady discharge frequency was approximately linearly related to current strength (cf. Granit, Kernell and Shortess 1963 a). Several cells were capable of setting up steady discharges only within this so-called “primary” range. In many other cells, steady repetitive firing was obtained even with stronger currents. There were in the latter two ranges of steady firing, the primary one referring to weak and a “secondary” referring to stronger stimulating currents, each approximately fitted by a separate straight line in the graphs relating impulse frequency to current strength. The straight line wich referred to steady firing within the secondary range had a 2–6 times steeper slope than the one characterizing the primary range. Motoneurones capable of maintained firing within the secondary range could reach steady firing rates of the order of 125 (88–195) imp/sec. The maximal impulse frequency within the primary range was about the same initially in the discharge as later on. The findings are discussed also with regard to the repetitive firing of reflexly activated motoneurones.

Definition of two Distinct Processes in Activation during Potassium-Induced Contractures of Frog's Skeletal Muscle

Abstract: The responses to rapid stretches applied just prior to or during potassium-induced contractures were investigated using small bundles of muscle fibres. In submaximal contractures induced by 27 or 42 mM KCl (in choline-Ringer's) the “resistance to stretch” (i. e., the extra tension recorded about 0.1 sec following the start of the stretch) and the tension developed without stretching followed different time courses. When stretched during the rise in tension the muscles always developed greater tensions than when the same stretch was applied before exposure to the elevated potassium. The “resistance to stretch” was small at the start of the contracture, it was maximal about halfway through the rise in tension and it declined slowly thereafter. By a proper selection of the amount of stretch and the instant of stretching it was possible to obtain tensions equal to or greater than the maximal tensions induced by isotonic KCl. In contractures induced by isotonic KCl the “resistance to stretch” was maximal near the start, it declined slowly during the rise of tension, and it declined rapidly during the fall in tension. These results suggest that the changes in elasticity (as indicated by the ‘resistance to stretch’) and the ability to develop tension resulted from two distinct processes and in potassium-induced contractures they follow different time courses which can be varied experimentally.

Direct studies on the disappearance of the transmitter and changes in the uptake-storage mechanisms of degenerating adrenergic nerves.

Abstract: Malmfors, T. and Ch. Sachs. Direct studies on the disappearance of the transmitter and changes in the uptake-storage mechanisms of degenerating adrenergic nerves. Acta physiol. scand. 1965. 64. 211–223. – The histochemical fluorescence method of Falck and Hillarp has been applied to a study of the disappearance of the endogenous noradrenaline (NA) and the uptake-storage mechanisms of the adrenergic nerves in the rat iris during the course of degeneration following axotomy. It was found that the transmitter stored in the terminals does not disappear gradually but quite suddenly and with various times of onset for the different systems of terminals. The uptake and accumulation of NA and α-methyl-NA were examined in untreated and reserpinized animals. These experiments show that the uptake-storage mechanisms in any given system of terminals operate up to a certain time without any obvious changes, but then deteriorate rapidly, at about the same time as the transmitter stores disappear. The axon membrane reabsorption mechanism seems to be lost somewhat prior to the storage mechanism of the transmitter granules, at the same time as degenerative changes seem to occur in the axon membrane, making possible a passive leakage of NA. – The results add further weight to the view that the cocaine-like component in the denervation supersensitivity is due to the loss of the uptake mechanisms. – Following the administration of bretylium the degenerative processes were delayed for about 8 hrs.

External Intercostal and Phrenic a Motor Responses to Changes in Respiratory Load

Abstract: The hypothesis that the fusimotor—muscle spindle system in its control of physiologically induced movements automatically adjusts the a motor activity to achieve“wanted” length changes in spite of some variations in load that may occur has been examined for the respiratory movements of external intercostal muscles and the diaphragm after bilateral vagotomy in cats under light pentobarbital anaesthesia. The afferent activity from intercostal muscle spindles increased in response to an increase in respiratory load produced by tracheal occlusion. Efferent intercostal a motor activity was reflexely enhanced in response to such an increase in load, an effect which was abolished after section of the dorsal roots of the same and adjacent segments. The efferent phrenic a motor activity and the electrical activity of the diaphragm did not show this response to tracheal occlusion indicating a principal difference in proprioceptive control of the external intercostal muscle and the diaphragm.

Accommodation in myelinated nerve fibres of xenopus laevis as computed on the basis of voltage clamp data.

Abstract: The equation system earlier derived from the voltage clamp analysis on myelinated nerve fibres from Xeonpus laevis was programmed for a digital computer. The response of the nerve model to linearly rising currents was computed for a number of quantitative modifications of the nerve model. The agreement between the computations and the earlier experimental results was qualitatively satisfactory. The quantitative agreement was not perfect but the discrepancies were not greater than what is expected from the known errors in the voltage clamp technique. The computations indicated that changes of any of the constants of the nerve model have effects on the rate of accommodation. The greatest effects were obtained by changing the inactivation of the sodium permeability. It was concluded, on the basis of the results obtained in the present and in the earlier investigation, that the slow excitability changes of the nerve fibres are well predicted by the equation system describing the ionic currents. Further, it was concluded that the normal variation in accommodation among myelinated nerve fibres from Xenopus laevis is accounted for mainly by variations in the rate constants ah although this may not be the only variable of importance. A variation in the turning on of the potassium permeability might also be significant.

The potassium ion as a vasodilator during muscular exercise.

Abstract: Calf muscles of cats were perfused with blood at constant flow rates. Tissue volume, blood flow, arterial and venous pressures were measured. Exercise was imitated by intermittent contractions of the muscles. During contractions the potassium concentration of the venous plasma from the calf increased by up to 100 per cent. Potassium salts infused intra-arterially at low rates dilated the vessels. It was calculated that the potassium released during exercise directly explains 25 to 65 per cent of the dilatation during exercise, the percentage being smallest when dilatation was slightest. There is presumably a diffusion gradient for potassium between tissue and blood with consequent underestimation of the role of the potassium ions, particularly when the dilatations are only weak. Therefore, 65 per cent probably comes closest to the true value of the proportion of the dilatation due to the potassium ions. Potassium infusions produced the same vascular response as exercise: a decrease of flow resistance was accompanied by a proportionate increase of the capillary filtration coefficient without signs of any increase in capillary permeability or dilatation of the capacitance vessels. Potassium is the only dilative substance hitherto found to produce exactly the same response as exercise.

On the nervous factors controlling respiration and circulation during exercise. experiments with curarization.

Abstract: In the steady state of work on a bicycle ergometer repeated i.v. injections of (+) tubocurarine produced a decrease in handgrip strength. In spite of this the intensity of work was maintained constant for 20 to 30 min. During this time pulse rate and blood pressure increased slightly and irregularity but the ventilation increased, both absolutely and in relation to the oxygen uptake, by up to about 50 %. The cardiac output was uninfluenced by the curarization. By adding CO2 to the inspired air the alveolar PCO2 was maintained at the normal exercise level. It is therefore assumed that all the known humoral factors controlling respiration in exercise must have been normal. The greatly increased ventilation must consequently have been caused by some nervous factors. The origin of these factors, whether central or peripheral, is discussed on the background of earlier experimental findings. A tentative explanation, based on the assumption that bicycle-work is performed by the mediation of the gamma-loop, is suggested. According to this the“nervous factor” of respiratory regulation in exercise may be the feed-back to the reticular formation of afferent impulses from the muscle spindles.

The importance of the legs in the thermoregulation of birds.

Abstract: The proportion of the total heat production of herons and gulls which at ambient temperatures ranging from—10° C to 35° C is dissipated to cold water or air surrounding their legs has been measured At low ambient temperatures less than 10 % of the metabolic heat is lost from the legs At higher ambient temperatures an increasing proportion of the metabolic heat is lost from the legs and at 35° C almost the entire heat production is dissipated through the legs Heat loss to water was found to be about four times higher than to air of the same temperature The degree of heat loss from the legs was shown to react within seconds to changes in ambient temperature Likewise, panting stopped immediately when the legs were irregated by cold water It is concluded that the naked legs of these birds serve as controlled heat conduits of great importance in thermoregulation

The pattern of muscular activity during the arm swing of natural walking.

Abstract: A telemetering device is described to record action potentials from muscles of the upper arm and the shoulder during the arm swing of natural walking. The forward swing is caused by activity in some inward rotators, the flexors remaining inactive. The posterior part of the deltoid and some outward rotators are responsible for the backward swing. During walk-turning electrical activity occurred in flexors inactive during straight walking accounting for the increased excursion of the forward swing which counteracts the torsional movement of the trunk. Step-related muscular activity persisted even when the arm was prevented from swinging.

Relationship between osmotic reactions and active sodium transport in the frog skin epithelium.

Abstract: The osmotic behaviour of the skin epithelium of the brown frog (R. temp.) has been investigated by microscopic measurement of thickness under different experimental conditions. Simultaneous measurements of skin potential and short-circuit current were made. Epithelial swelling was induced by hypotonicity of the inside but not the outside bathing solution, whereas shrinkage was brought about by hypertonicity of either inside or outside bathing solutions, although the tonicity of the inside bathing solution dominates the osmotic reponse. Shrinkage can also be induced by lowering the potassium concentration of the inside solution. Complex shrinkage and swelling reactions are produced by addition of diffusible substances like urea to either bathing solution. In practically every instance shrinkage leads to inhibition of the short-circuit current (and thus of the active sodium transport), whereas swelling of the epithelium gives rise to increased active sodium transport. The skin potential is related to swelling and shrinkage in a more involved fashion. In general hypertonicity of the outside bathing solution leads to a violent drop in skin potential. The observations indicate that hypertonicity of the outside solution increases the permeability of the outer epithelial boundary to passively diffusing electrolytes and to water.

A comparison of neural and psychophysical responses to taste stimuli in man.

Abstract: Diamant, H. B. Oakley, L. Strom, C. Wells and Y. Zotterman. A comparison of neural and psychophysical responses to taste stimuli in man. Acta physiol. scand. 1965 64. 67–74. – Electrophysiological records of taste activity have been obtained from the chorda tympani nerve of otosclerotic patients. When possible, preoperative psychophysical responses to taste stimuli were also obtained. The summated chorda tympani discharge to 0.2 M NaCl adapts completely and the time required agrees with psychophysical reports. Psychophysical estimates of the sweetness of different sugars correspond closely with nerve response magnitudes. Gymnema extract abolishes both the sweet sensation and the nerve response to sweet tasting chemicals. The total sum of taste activity in the entire chorda tympani nerve appears to be an important determinant of the psychophysical responses. There are large individual differences in the relative size of the neural response to different taste stimuli. Responses to ethyl alcohol are described.

On the Competition between Metabolic Vasodilatation and Neurogenic Vasoconstriction in Skeletal Muscle1

Abstract: Using a plethysmographic method combined with recording of blood flow and, at times, recording of the volume of blood in the calf of the cat with an isotope technique, the responses of the resistance vessels, of the capillary filtration coefficient and of the capacitance vessels were studied when the vessels were subjected to the antagonistic influences of muscular exercise and vasoconstrictor fibre activity. At the higher frequencies of stimulation used sympathetic activation caused an equally marked reduction of blood flow during exercise as during rest, but during exercise the response of the resistance vessels subsided within a few minutes to become steady at a level only a little above starting level despite continued stimulation. The capillary filtration coefficient, already increased during exercise, was affected, and then increased still further only when the sympathetic were stimulated at such frequencies as impeded blood flow markedly. Sympathetic stimulation during exercise increased the tone of the capacitance vessels—a response that did not weaken at all so soon as that of the resistance vessels. It is concluded that the resistance vessels and particularly the precapillary sphincters are more sensitive to vasodilator metabolites locally released during exercise than to the vasoconstrictor fibre supply, while the reverse is true for the capacitance vessels.

Cardiovascular and metabolic response to infusions of prostaglandin E1 and to simultaneous infusions of noradrenaline and prostaglandin E1 in man. Prostaglandin and related factors 35.

Abstract: Bergstrom, S., L. A. Carlson, L. G. Ekelund and L. Oro. Cardiovascular and metabolic response to infusions of prostaglandin E1 and to simultaneous infusions of noradrenaline and prostaglandin E1 in man. Acta physiol. scand. 1965. 64. 332–339. – Prostaglandin E1 (PGE1) was infused at a rate of 0.1–0.2 μg/kg/min into 3 healthy, fasting male subjects for 20 min. No consistent changes in arterial pressures occurred. The heart rate increased about 20 beats/min. The concentration of free fatty acids (FFA) and of glycerol in plasma increased. A slight increase in oxygen consumption was observed. PGE1 infused simultaneously with noradrenaline to 2 healthy, fasting male subjects reduced the increase in arterial pressures seen when only noradrenaline was infused to these subjects. Furthermore, PGE1 completely inhibited the noradrenaline induced bradycardia. The increase in the concentration of FFA and glycerol in plasma caused by noradrenaline was only slightly reduced by PGE1. PGE1 had no effect on the calorigenic effect of noradrenaline.

Studies on Some Systems of Adrenergic Synaptic Terminals in the Abdominal Ganglia of the Cat

Abstract: Hamberger, B. and K.-A. Norberg. Studies on some systems of adrenergic synafhc teminals in the abdominal ganglia of the cat. Acta physiol. scand. 1965. 65. 235–242. — The course of adrenergic fibres forming synaptic structures in certain visceral ganglia of the cat has been studied with the histochemical fluorescence method of Falck and Hillarp, after selective denervation. The adrenergic synaptic terminals in the intramural ganglia of the colon have their cell bodies in the inferior mesenteric ganglia. The same holds for most of the adrenergic muscle innervation in the bladder trigonum. The adrenergic synaptic terminals in the intramural ganglia of the bladder originate mainly in cell bodies in these or other pelvic ganglia. Adrenergic vasomotor nerves reach the bladder via the pelvic nerves. The adrenergic synaptic terminals in the inferior mesenteric ganglia are mainly of intraganglionic origin. These terminals seem to constitute important and widespread systems for the modulation of ganglionic impulse transmission.

Distribution and function of adrenergic nerves in the rabbit fallopian tube.

Abstract: : Contents: Distribution of noradrenaline and adrenaline and of adrenergic nerve terminals in the fallopian tube of the rabbit; Functional studies on the adrenergic innervation of the circular muscles of the rabbit oviduct.

Vagal relaxation of the stomach. Experimental re-investigation of the concept of the transmission mechanism.

Abstract: Martinson, J. Vagal relaxation of the stomach. Experimental re-investigation of the concept of the transmission mechanism. Acta physiol. scand. 1965. 64. 453–462. – The vagus nerves contain efferent fibres capable of relaxing the corpus and fundus of the stomach. In experiments on cats this atropine-resistant effect has been shown to differ in several respects from relaxation elicited by sympathetic stimulation or infusion of catecholamines. The vagal responses are more potent, their latency is shorter, and maximum response is attained at definitely lower frequencies. The responses to sympathetic stimulation wears off much more rapidly after the end of stimulation than does vagally induced gastric relaxation. Finally, the sympathetic or catecholamine gastric responses are more or less completely blocked by guanethidine or nethalide, which have hardly any effect on the vagal relaxation of the stomach. Hexamethonium inhibits vagal relaxation, and seems to be potentiated by atropine. It is concluded that the relaxation of the stomach on excitation of“high-threshold” efferent vagal nerve fibres is mediated via preganglionic vagal fibres, which do not exert their effect by any adrenergic mechanism. It is still not possible to say what peripheral mechanism is actually responsible for this long-lasting gastric relaxation.

Fusimotor Activity in the Spinal Cat

Abstract: Fusimotor activity has been assessed from the changes in the response of muscle spindle receptors to a linear stretch and release of the muscle at various levels of fusimotor drive. The background fusimotor activity of the spinal cat caused an increased dynamic responsiveness of primary endings of ankle flexor as well as the ankle extensor muscles. Further, dynamic activation of both flexor and extensor primary endings was observed during electrical stimulation of the ipsilateral saphenous and the contralateral lateral popliteal nerve. Definite signs of activity in static fusimotor neurones were not found in spinal preparations. The observations support the hypothesis of an independent control of the static and dynamic properties of primary endings of the muscle spindle. It is suggested that the activity in the dynamic fusimotor system largely is supported by dorsal root inflow, whereas the static fusimotor system mainly depends upon descending suprasegmental activation.

The Adrenergic Innervation of the Eye as Demonstrated by Fluorescence Microscopy

Abstract: Malmfors, T. The adrenergic innervations of the eye as demonstrated by fluorescence microscopy. Acta physiol. scand. 1965. 65. 259–267. — Ocular tissues from different species (mouse, rat, guinea pig, rabbit, cat and monkey) have been examined with the fluorescence method of Falck and Hillarp, which visualizes the adrenergic postganglionic sympathetic nerves. In addition to the generally accepted innervation of the vessels (particularly in the vascular layer of the eye) and of the dilator, there were found also an adrenergic innervation of the sphincter and an adrenergic ground-plexus among the capillaries in the choroid and the ciliary body. There was not, on the other hand, found any adrenergic innervation of the retinal vessels (except in the optic papilla) and no clear innervation of the ciliary mudcle. All the adrenergic nerves to the eye seemed to arise from the upper cervical ganglion. The present observations are discussed in relation to earlier physiological and pharmacological findings.