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At least 271 records · Page 15Linked to original sources
PubMed1986

Extended attack from a resident conspecific is critical to the development of long-lasting analgesia in male intruder mice.

Recent studies have shown that intruder mice display qualitatively different forms of analgesia in response to social encounters with resident conspecifics. An acute (non-opioid) reaction is evident when display of defeat is used as test criterion whereas a much longer-lasting (opioid) response is observed when this criterion is exceeded. Neither reaction can be readily attributed to the effects of physical stimulation per se. Two studies were conducted to determine the critical stimulus leading to a 'switchover' from non-opioid to opioid analgesia in intruder mice. The pattern of results indicates that temporal factors per se are unimportant but that extended exposure to attack is essential to the development of an enduring (opioid-typical) analgesia. It is argued that this finding is consistent with the uncontrollability hypothesis which asserts that opioid analgesia is a consequence of a failure in behavioural coping strategies.

Aggression↗
PubMed1996

Intestinal injuries caused by experimental palytoxicosis in mice.

Intestinal injuries in mice caused by i.p. administration of palytoxin at 1 microgram/kg were studied microscopically. Within 1 hr, bleeding started from small intestinal villi. At 6 hr, congestion in the villi and edema in the lamina propria in the crypt layer developed prominently. Edema and necrosis of lamina propria in the villus appeared after 16 hr. At 24 hr, villi lost their epithelial cells and then their length decreased to 1/4 to 1/8 of normal. Diarrhea was seen after 16 hr, accompanying severe peritonitis. Hypersecretion of mucus from the large intestine was considered to be physically stimulated by peritonitis, which then induced diarrhea.

Acrylamides↗
PubMed1984

Characteristics of saccades in human infants.

Infants (14-151 days) and adults were shown two-dimensional geometric forms or stimuli from a set of highly textured patterns. Their eye movements were recorded by an infrared corneal reflection eye movement recorder as they freely scanned the stimuli. For both infants and adults, linear relationships were found between the peak velocities of fast eye movements and their amplitudes (main sequences). Infants viewing texture stimuli had main sequences with slopes comparable to those of adults. Infants viewing simple geometric forms made slower saccades. They also showed more eye movement oscillations which analyses showed were probably back-to-back saccades. Both the slower saccades and saccadic oscillations were attributed to factors related to the attentional value of the stimuli.

Adolescent↗
PubMed1983

Autonomic drug effects and gastric secretion in a new experimental model of stress ulcers in rats.

A psychological procedure which does not involve the application of physical stimulation was used to produce gastric ulcers experimentally. Ulceration was induced in rats by exposing the animals to the aggressive attacks of rats treated with 6-hydroxy-dopamine (6-OHDA). Gastric secretion and the effects of autonomic drugs on ulcer formation were investigated. Atropine methylbromide did not significantly inhibit the occurrence of erosions. Phentolamine or hexamethonium bromide significantly inhibited the production of erosions, and combined administration of an anticholinergic agents and alpha-blocking agent led to a complete inhibition, with no notable behavioral change. In case of pylorus ligation, gastric secretion during exposure to attack of 6-OHDA-treated rats was significantly less than that in the controls. We suggest that the sympathetic nervous system plays an important role in the production of gastric erosions, as induced by the methods reported in this study.

Animals↗
PubMedDate not supplied

Ascorbic acid in the brain.

Ascorbic acid is highly concentrated in the central nervous system. Measurement of the extracellular concentration of ascorbate in animals, mainly by the technique of voltammetry in vivo, has demonstrated fluctuation in release from neuropil, both spontaneously and in response to physical stimulation of the animal and to certain drugs. Although in the adrenal medulla ascorbate is co-released with catecholamines, release of ascorbate from brain cells is associated principally with the activity of glutamatergic neurones, mainly by glutamate-ascorbate heteroexchange across cell membranes of neurones or glia. This phenomenon is discussed in relation to a possible role of ascorbate as a neuromodulator or neuroprotective agent in the brain.

Animals↗
PubMed1986

Parietal and frontal eye field neglect in the rat.

Rats were given unilateral aspiration lesions of parietal, medial frontal, or dorsolateral frontal (motor) cortex and then tested for visual, auditory and tactile neglect, and for circling. All medial frontal lesion animals showed contralateral neglect in each modality and circled ipsiversively. The parietal lesion rats initially displayed contralateral visual and auditory neglect as severe as that in the medial frontal group. Three weeks after the lesions, the parietal group had a smaller residual deficit on the visual test than the medial frontal group. In the first week, parietal animals responded less than the medial frontals to stroking the vibrissae but were more responsive to mild pinching of a toe contralateral to the lesion side. In striking contrast to the medial frontal animals, the parietal group circled strongly to the contralateral side. No rat with a motor cortex lesion neglected or circled preferentially. Like medial frontal cortex, unilateral parietal lesions also produce neglect and circling, but there are important features distinguishing unilateral lesion effects in these two regions.

Acoustic Stimulation↗
PubMed1996

Apomorphine produces an acute dose-dependent therapeutic effect on neglect produced by unilateral destruction of the posterior parietal cortex in rats.

The neglect syndrome is a complex and devastating neurological disorder typically induced by unilateral destruction of one of three regions of the neocortex: the inferior parietal lobule, the dorsolateral prefrontal cortex or the cingulate cortex. Previous studies of neglect using a rodent model have indicated that disruption of dopaminergic mechanisms may underlie neglect. However, the pharmacological results were obtained using a rodent prefrontal model of the syndrome (medial agranular cortex), whereas the majority of cases of neglect in humans are produced by unilateral destruction of the posterior parietal cortex (inferior parietal lobule). The present study examined the effects of administration of the dopamine receptor agonist apomorphine on neglect induced by unilateral destruction of the posterior parietal cortex (PPC) in rats. The results indicated that administration of apomorphine produced a significant dose-dependent decrease in the severity of neglect. The results support the contention that neglect induced by cortical damage may be produced by a disruption of dopaminergic mechanisms, and that the PPC may be one component of a cortical system for directed attention.

Acoustic Stimulation↗
PubMed1984

Capacitative pulsed electric stimulation of bone cells. Induction of cyclic-AMP changes and DNA synthesis.

Pulsed electric stimulation, coupled capacitively to bone cells isolated from rat embryo calvaria, caused changes in the intracellular level of cyclic AMP and enhanced DNA synthesis. The capacitive method of electrical stimulation was characterized in terms of displacement currents (0.7-4.0 A) and voltages (10-54 V/cm) prevailing in the stimulation chamber. Changes, both in cyclic AMP and in incorporation of [3H]thymidine into DNA, were correlated with the strength of the applied electric field. Unlike the mechanical stimulation of bone cells, the electrical stimulus was not mediated by de novo synthesis of prostaglandins. The findings suggest that cyclic-AMP changes, induced by the capacitive electrical stimulation of bone cells, trigger DNA synthesis.

Animals↗
PubMed1994

The self-regulation of slow potential shifts and evoked potentials: interrelationships in response to somatosensory stimulation.

Research on the effects of the self-regulation of event-related potentials (ERP) has failed to investigate the possible interactions and contributions of slower cortical events such as contingent negative variations (CNV) and slower DC level changes. The present study attempted to investigate such interactions by independently conditioning the ERP 200 ms poststimulus (P200) and the CNV while recording both potentials simultaneously; DC level measures were also recorded. 30 subjects attempted to increase (uptraining) or decrease (downtraining) either P200 or CNV in response to sub-painful somatosensory stimulation in a biofeedback paradigm. Following the training sessions, P200 downtrainees reported a significant decrease in their detection thresholds for the somatosensory stimuli (i.e., increased sensitivity). These results agree with some prior findings that decreased ERP amplitude in individuals is indicative of greater sensitivity in subjective pain reports. Although uptraining resulted in larger P200 amplitudes than downtraining, the difference in amplitudes between groups was not significant. CNV uptrainees achieved a higher level of pain tolerance following training. The increased CNV negativity may be associated with increased specific attentional processes that facilitate the subjects' control of, or response to, pain. CNV trainers showed a significant interaction of training over blocks of trials. Generally, there was a significant inverse correlation of P200 and CNV; as CNV amplitude became more negative, the P200 amplitude increased. DC negativity level increased over blocks for all conditions. Results indicate a complex relationship between P200, CNV and pain sensitivity. Both P200 and CNV processes are involved in pain perception, but in apparently different ways, i.e., P200 with sensitivity and CNV with tolerance.

Adolescent↗
PubMed1996

Simple-spike activity of floccular Purkinje cells responding to sinusoidal vertical rotation and optokinetic stimuli in alert cats.

To understand how the cerebellar flocculus is involved in the processing of semicircular canal signals in the vertical vestibulo-ocular reflex (VOR), we analyzed the simple-spike activity of floccular Purkinje (P) cells that was modulated by sinusoidal pitch rotation, and then analyzed their activity during presentation of sinusoidal vertical optokinetic stimuli in alert, head-fixed cats. The great majority of P cells also responded to optokinetic stimuli with peak discharge near peak stimulus velocity. Eighty percent of P cells that responded to both pitch and optokinetic stimuli showed increased activity when the directions of the resultant eye movements were the same. During rapid modification of the VOR induced by visual pattern movement, modulation amplitudes of the cells tested increased together with the eye velocity increase. Maximal activation directions of these cells studied during vertical rotation in many planes were near the vertical canal planes, similar to those in our previous studies. The remaining 20% of P cells showed increased discharge for the same direction of stimulus movement. These results suggest that the activity of the majority of pitch-responding P cells contains, at least partly, a vertical eye velocity component during presentation of vestibular or optokinetic stimuli in addition to canal inputs during pitch rotation.

Animals↗
PubMed1985

The effect of stimulus significance on relatively sustained (tonic-like) and relatively transient (phasic-like) aspects of electrodermal, heart rate, and eyeblink response.

To examine the influence of stimulus significance on more sustained as well as transient aspects of electrodermal, cardiac (HR), and eyeblink response, a 21-sec tone was sounded in one ear or the other. A click occurred during many tones, and a light followed offset by 9 sec. Four groups were studied: one pressed a pedal immediately on hearing any click; another only on click during tone in a specified ear; a third also responded only to the specified ear, but withheld press until the light; a fourth listened without any response. Results confirmed the important role of stimulus significance in each system whether between- or within-subject comparisons were made. Sustained responses were seen only when a significant signal was sought, involving in each case sustained HR deceleration, slowed blink rate, and heightened electrodermal level. Transient response to click and light also appeared only when there were significant signals. Response to tone-onset gave more ambiguous results. ANOVAs of response magnitude suggested that onset of nonsignificant tones might have elicited ORs, while binomial tests indicated these were not elicited with better than random frequency anywhere but on those trials occurring more frequently at the experiment's onset. Interpretations consistent with both the significance hypothesis and with a distinction between automatic and voluntary ORs can be made only here. Motor response had no effect on electrodermal or eyeblink response, and on HR was associated only with increased acceleration 1-2 sec after pedal-press. Studies using small motor responses to establish stimulus significance are therefore not likely to be substantially biased by the response itself.

Acoustic Stimulation↗