Archivio di fisiologia最新文献

Three methods for obtaining passive avoidance conditioned responses of different strength are described. The first method consists of delayed reinforcement, constituted by a foot-shock, in the conditioning trial. The second method corresponds to the "detention" procedure, through which the animal is kept in one part of the apparatus for some time, after the conditioning trial. The third method consists of using foot-shocks of different strength in the conditioning trial. This method, however, is not advisable in most cases, since it produces strong differences in the subjects' level of arousal after conditioning and therefore a different reactivity to the various treatments.

The distribution in the dorsal roots of proprioceptive afferent fibres from tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of the rat and the physiological characteristics of the related nervous endings have been investigated. Axons of proprioceptive endings from TA and EDL were found mainly in L4, only a few in L5. Afferent proprioceptive fibres from posterior superficial crural muscles (gastrocnemius, soleus, plantaris) pass mainly through root L5; axons of extrafusal motor units are distributed in a similar way. Sensory endings in TA and EDL were examined, after identification, by means of their static threshold to passive stretch. Almost all steady-state responses to passive stretch, within the physiological extension range, came from muscle spindles. 1-2 to 20 g loads were necessary to obtain steady-state discharges from these receptors. Spindle endings were classified as primary or secondary by measuring the conduction velocity of the afferent fibres, and according to the features of their passive behaviour. Threshold difference cannot be regarded as a fundamental characteristic, because of the considerable overlapping of the values obtained from the two types of endings. Conduction velocities of 50 to 80 m/sec for primary and of 20 to 40 m/sec for secondary afferent fibres were observed. Afferent fibres conducting at intermediate velocity often behave like primary ones. As a rule, tendon organs showed a higher static threshold to passive stretch; the loads employed only rarely elicited a steady-state response. As for these receptors, which usually showed marked adaptation characteristics, passive force is a less effective stimulus than active contraction. The conduction velocity range of afferent fibres from tendon organs is the same as that of primary afferents. The results are discussed.

Fifty-eight adults, nearly all male, aged between 35 and 50, with slight bronchiopneumopathy in a state of functional compensation, were subjected to hypoxia by rerespiration. Heart rate and oxyhaemoglobin saturation were observed. In nearly all cases, hypoxia caused an increase in heart rate that varied considerably from subject to subject, but seemed more marked between the 1st and 2nd minute after start of the trial. Normalization of heart rate, similarly very variable, reflected the increase phase and was complete in periode varying between 30 and 210 seconds. It may be supposed that as regards heart rate the wide variety of responses to the same stimulus is due to individual states of equilibrium of a predominantly vegetative nature. There was no relation between duration of the hypoxia trial, extent of desaturation and time of resaturation in air because the rate of haemoglobin desaturation and resaturation varied from case to case.

Origin and distribution of pre- and postsynaptic fibres in the sympathetic trunk of Rana esculenta (from ganglion 3 to ganglion 10) have been investigated by means of extracellular recordings. Two systems conducting efferent information appear to exist: 1) a system made of faster conducting fibres (B group pre- and postsynaptic fibres); presynaptic fibres originating from a very high monosegmental source (4th spinal root); postsynaptic fibres leave the sympathetic chain plurisegmentally (rami communicantes 5-10); 2) a system made of slower conducting fibres (C group pre- and postsynaptic fibres) originating plurisegmentally from spinal roots 5-8. Intracellular recordings have shown that: 1) integrative processes take place in the amphibian sympathetic trunk, as in the mammalian one, but are quantitatively lesser. Homonomous (B-B) and heteronomous (B-C) convergence has been observed in B neurons, and also the convergence of a collateral of a C postsynaptic axon on B neurons. 2) posthumous depolarizations are present: these are events modulating the activity of sympathetic neurons. In B neurons posthumous depolarization follows orthodromic responses, and a late posthumous depolarization can be seen in B and C neurons following either ortho- or antidromic stimulation.

The concentration of some end products and the activity of some enzymes participating in carbohydrates metabolism were examined in bovine carotid artery contracted by KCl. Oxygen consumption decreased significantly, anaerobic glycolysis and tissue lactic acid content increased during the KCl contraction. The hexosamines and the uronic acids producing ability of the KCl contracted artery were also higher. During contraction the SDH activity decreased in a smaller degree, cytochrome oxydase activity in a much more important degree. On the basis of our results we can conclude that the complete oxydation pathway of carbohydrates degradation, as mucopolysaccharides synthesis and degradation have an important part in the energy metabolism, but anaerobic glycolysis is the most important pathway to produce energy for the KCl contraction of vascular smooth muscle.

Lengthening the time interval between the conditioned stimulus and the unconditioned stimulus increases the number of active avoidance conditioned responses in subjects that have been trained to a stable level of performance in many previous conditioning sessions. In the present research, rats chosen from a population specially selected for low rates of avoidance conditioning have been used. In addition to this characteristic, subjects were chosen for the exhibition of an apparent absence of retention from one day to another. The dependency of the number of conditioned responses on the time interval between conditioned stimulus and unconditioned stimulus may lead to wrong evaluation of the subjects' conditioning level. In fact, the level of conditioning may be attributed to either learning or memory processes when in many cases it is determined only by the latency time of the conditioned response. The conditioned response has no possibility of manifesting itself when its latency time exceeds in length the time interval between conditioned stimulus and unconditioned stimulus.

We examined first the behavior of a single animal (Macacus Rhesus), partially free to move on a Brady chair, before and after direct electrical stimulation of the amygdala and the hippocampus; then the social behavior of two animals, completely free to move in a large behavioral cage, before and after stimulation, by radio, of the amygdala. Certain ventromedial areas of the amygdala have a short and long term inhibitory effect on feeding and social behavior and the hippocampus has a short and long term facilitating effect on feeding behavior, especially during the after discharge.

The aim of this study is to see if some drugs are able to lodge blood in specific organs, in the Rat. The metodic is the follow: the rat's carotid is connected to a container of saline plasma; the animal is fastened to a balance with central fulcrum; by the relation between the movements of the balance and the liquid entered and come out from the container, because of the action of the drugs on the animal, it is possible to stabilish the part of the body from which the blood is moved. The prevailing effect of 0,25-1 mug/kg doses of isoprenalin is an accumulation of blood in the liver: this blood comes from caudal parts to these organs. The enteramin's effect, for doses of 3-30 mug/kg, is an accumulation of blood in the liver and in the torax. The carbamylcholin's effect, for doses of 1-4 mug/kg, is an accumulation of blood in the abdomen and partially in the liver; this blood comes from cranial parts to the abdomen.