Ablation In Rats Research Articles

Altered local cerebral glucose utilization by unilateral frontal cortical ablations in rats

Altered local cerebral glucose utilization by unilateral frontal cortical ablations in rats

Altered local cerebral glucose utilization by unilateral frontal cortical ablations in rats

Alterations in local cerebral glucose utilization (LCGU) following ablations of the unilateral frontal cortex in rats were studied to elucidate the effect of the lesion on the functional activity in the related cerebral structures. Frontal cortical ablations (areas 2, 4, 6 and 10) were made by aspiration on the left side, and LCGU was evaluated at 7 days after the operation, using the [14C]deoxyglucose method. Significant decreases in LCGU in rats with unilateral frontal cortical ablations, were observed in the ipsilateral thalamic nuclei (ventroanterior-ventrolateral (VAL), ventrobasal (VB), reticular), red nucleus and pontine nucleus. The ipsilateral globus pallidus showed a significant LCGU increase. The contralateral cerebellar cortex showed a tendency toward a decrease in LCGU. The striatum, which receives direct projections from the frontal cortex, showed no LCGU change. These results indicated that ablations of unilateral frontal cortex in rats produced LCGU changes in the cerebral structures which have direct or indirect neuronal connections with the ablated area. These LCGU changes were, for the most part, brought about by alteration in the neuronal activity. Particularly, the LCGU increase in the globus pallidus which receives transsynaptic neuronal input from the frontal cortex, without changes in the striatum, which receives direct projection, was attributed to the functional alteration of the globus pallidus produced by the cortical ablation. Destructive lesion of a cerebral structure, therefore, does not necessarily cause functional depressions in the pertinent structures, but it may enhance the function of some structures, depending on the functional characteristics of each neuronal connection and functional organization of those structures.

Bilateral branching contributes minimally to the enhanced ipsilateral projection in monocular Syrian golden hamsters

Studies of the plasticity of retinal projections following neonatal eye ablations in rats and hamsters have demonstrated an enhanced ipsilateral projection which affects both the terminal fields and the number of ipsilaterally projecting cells. The enhancement has been attributed to an excess of bilateral branching by single optic nerve axons, but this claim was not supported by the present study. Double retrograde labels were used to quantify the ipsilateral enhancement and measure the extent of bilateral branching in hamsters with neonatal eye removals. In 19 normal Syrian golden hamster retinas the average number of bilaterally projecting retinal ganglion cells (BPRGCs) was 7.4 (SD = 3), and the average number of ipsilaterally projecting retinal ganglion cells (IPRGCs) was 1349 (SD = 478) (Hsiao, K., G. M. Sachs, and G. E. Schneider (1984) J. Neurosci. 4: 359-367). In nine retinas of hamsters with removal of one eye at birth, the average number of BPRGCs was 25.3 (SD = 9.2), and the average number of IPRGCs per retina was 2036 (SD = 414). Although the increase in BPRGCs is statistically significant, it accounted for only 2 to 3% of the 51% increase in the number of IPRGCs. Various possible mechanisms underlying the formation of the enhanced projection are enumerated, and it is concluded that the predominant mechanism is a reduction of cell death in the developing population of IPRGCs. The responses of IPRGCs and BPRGCs to early eye enucleations were also examined with respect to age at enucleation and cell size. No difference in size was found between IPRGCs and BPRGCs in monocular hamsters compared to normal hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects on visual acuity of neonatal or adult tectal ablation in rats.

Tectal ablation in neonatal rats leads to retrograde degeneration of retinal ganglion cells whereas similar damage in adults does not. We show here that the behavioral effects are comparably different. When rats with neonatal tectal ablation are tested as adults they are impaired in learning a discrimination between vertical and horizontal stripes and their visual acuity for square-wave gratings is slightly but significantly reduced.

Effect of motor and premotor cortex ablation on concentrations of amino acids, monoamines, and acetylcholine and on the ultrastructure in rat striatum. A confirmation of glutamate as the specific cortico-striatal transmitter.

At 1, 2, and 4 weeks after unilateral premotor and motor cortex ablation in rats, a significant and lasting decrease in glutamate levels in the ipsilateral versus contralateral striatum was observed. A significant corresponding fall in aspartate was seen only after 1 week. In contrast, there was a large increase in the striatal concentrations of lysine, threonine, alanine, and glutamine 1 week after the cortical ablation. This correlates with the extensive glial proliferation in the deafferented ipsilateral striatum. Four weeks after cortical ablation the GABA concentration was significantly increased. There was no decrease in other putative transmitters (dopamine, serotonin, acetylcholine, glycine and taurine), nor was a glutamate decrease observed in the hippocampus or in the hypothalamus, which do not receive direct premotor and motor cortical inputs. Both biochemical and morphological evidence for a minor contralateral cortico-striatal projection was obtained. Correlating with the fall in glutamate, ultrastructural observations indicated the degeneration of two types of striatal synapses, i.e., those of the axo-spinous type III and of the axo-dendritic type VII. Frontal cortex ablation clearly affects, in opposite directions, the metabolism of various striatal amino acids but not that of acetylcholine and the monoamine transmitters. The results strongly support the view that glutamate is the transmitter of the cortico-striatal fibers.

Hippocampectomy attenuates the reduction of operant rate produced by d-amphetamine

Hippocampal ablations in rats were found to significantly attenuate the response-decreasing effect of d-amphetamine observed when control animals perform on the fixed ratio (FR) component of a multiple FR, extinction (EXT) schedule under the drug’s influence but had no effect on the ability of the drug to facilitate responding on the EXT component. Separate experiments indicated that hippocampal ablation neither increased nor decreased the ability of amphetamine to produce anorexia, stereotypy, or increases in locomotion. The data from these experiments are interpreted to indicate that the hippocampus is one structure involved specifically in the ability of amphetamine to lower response rate on an FR schedule and that the hippocampus may be part of the neural substrate of the phenomenon of “rate dependency,” which is one predictor of the behavioral action of amphetamine. These data may be interpreted within a theoretical framework that ascribes to the hippocampus a function in altering behavior when either the internal or the external environment changes.

Changes in salt intake after lesions of the area postrema and the nucleus of the solitary tract in rats

Several reports have linked the area postrema (AP), a circumventricular organ in the dorsal medulla, to the control of sodium regulation. To clarify its role further we examined the effects of AP ablations in rats on sodium intake as well as on sodium output. Eighteen experimental rats received lesions to the AP while 6 control rats received sham lesions. After the lesions we gave the animals a two-bottle preference test between water and various molar concentrations of NaCl (0.03, 0.1, 0.3, 0.5), glucose (0.1, 0.3) or KCl (0.1, 0.3) solutions. Rats with AP lesions consumed supranormal amounts of NaCl solutions, but their intakes of glucose and KCl solutions were not significantly different from those of control rats. These changes in intake were apparently not secondary to changes in sodium output. Urinary sodium and potassium levels were the same for both groups of rats while on a normal, sodium-replete diet or on a sodium-free diet. Anatomical analyses revealed a significant correlation between the size of the lesion and the animals' salt intake (NaCl, KCl). Only when the lesions destroyed the AP without appreciable damage to the adjacent nucleus of the solitary tract (NST), a sensory relay for gustatory and visceral afferents, was there a significant tendency for rats to consume more salt solution. These changes in intake cannot be accounted for by lesioned produced deficits in gustatory function. The data were discussed with regard to possible hemodynamic effects of the lesions.

Deficits in contralateral and ipsilateral forepaw motor control following unilateral motor cortical ablations in rats

Two force transducers which were interfaced with a minicomputer were used as operant manipulanda to assess changes in peak force and rate of response produced by unilateral motor cortical lesions in rats. Spatial arrangement of the manipulanda permitted a subject to respond on Transducer I exclusively with his left forepaw and on Transducer II exclusively with his right. Permanent deficits as measured by both force and rate of response were observed for the limb contralateral to the lesion. In the forelimb ipsilateral to the lesion rate of response was severely depressed immediately following the lesion and, although there was marked recovery during the 10–12 days following surgery, post-lesion rates never attained pre-lesion levels.

Hippocampal lesions and immobility responses in the rat

The present study was conducted to compare the effects on several immobility reactions of hippocampal ablation in rats. Hippocampal lesions were found to increase significantly the duration of restraint-induced immobility, but these same lesions significantly increased movement in response to footshock and in an open field, indicating a reduction in the tendency for rats with hippocampal lesions to become immobile in these situations. These results are interpreted as indicating that hippocampal lesions in animals do not inevitably lead to a decreased tendency to become immobile in stressful situations and that the hippocampus in the adult rat inhibits behaviors which immature rats demonstrate more readily than mature rats.

DRL performance following anteromedial cortical ablations in rats

DRL performance following anteromedial cortical ablations in rats

Time-dependent changes in amphetamine self-administration following frontal cortex ablations in rats.

Rats were trained to intravenously self-administer d-amphetamine (.01 mg/kg/reward infusion) during daily 1-hr. testing sessions. Following removal of frontal cortex, rates of d-amphetamine self-administration were higher at early (3-5 days) postoperative intervals but lower at later (2-4 wk.) postoperative intervals. These and other results indicated that, as a function of time after surgery, frontal rats are first hyposensitive and then become increasingly hypersensitive to the rewarding effect of d-amphetamine.

96) - Effects of locus coeruleus lesions on hyperemotionality induced by olfactory bulb ablations in rats

96) - Effects of locus coeruleus lesions on hyperemotionality induced by olfactory bulb ablations in rats

Effects of frontal ablations in auditory discrimination in the rat.

Summary The present study employed a free operant discrimination procedure in studying the effects of frontal ablations in rats. Two groups of Ss were trained on a multiple fixed ratio (FR) 3 extinction schedule, and then the experimental group received frontal lesions. Following recovery they were returned to the multiple schedule. It was found that for the experimental group there was a significant loss in discrimination following frontal lesions. These results support a study done by Weiskrantz and Mishkin (8).

Hyperemotionality induced by lesions in the olfactory system of the rat

In order to clarify the neural mechanisms underlying the hyperemotionality induced by bilateral olfactory bulb ablations in rats, changes in emotional behavior were measured after various parts of the secondary olfactory structures had been lesioned and olfactory bulb ablations had been carried out. When the anterior olfactory nuclei, lateral olfactory tracts and prepiriform cortices were bilaterally lesioned simultaneously with olfactory bulb ablations, many rats died from lack of food intake, while on the contrary, the rats with bilateral lesions in the olfactory tubercle, anterior olfactory nuclei and olfactory bulb developed marked hyperemotionality immediately after the lesioning. Hyperemotionality of the latter rats included not only hyperreactivity similar to that observed in the septal rat but also a muricide of 90% in incidence, which is similar to rats with olfactory bulb ablations. From these results, it can be concluded that changes in the activity of the olfactory tubercle were the most important for the development of hyperemotionality following bilateral ablations of the olfactory bulb in the rat.

Hyperemotionality induced by lesions in the olfactory system of the rat.

In order to clarify the neural mechanisms underlying the hyperemotionality induced by bilateral olfactory bulb ablations in rats, changes in emotional behavior were measured after various parts of the secondary olfactory structures had been lesioned and olfactory bulb ablations had been carried out. When the anterior olfactory nuclei, lateral olfactory tracts and prepiriform cortices were bilaterally lesioned simultaneously with olfactory bulb ablations, many rats died from lack of food intake, while on the contrary, the rats with bilateral lesions in the olfactory tubercle, anterior olfactory nuclei and olfactory bulb developed marked hyperemotionality immediately after the lesioning. Hyperemotionality of the latter rats included not only hyperreactivity similar to that observed in the septal rat but also a muricide of 90% in incidence, which is similar to rats with olfactory bulb ablations. From these results, it can be concluded that changes in the activity of the olfactory tubercle were the most important for the development of hyperemotionality following bilateral ablations of the olfactory bulb in the rat.

A retention loss following septal ablations in the rat

Bilateral septal ablations in rats increased resistance to extinction when made before training, but decreased resistance when made after training. These contrasting effects were considered to demonstrate that septal ablations affect retention as well as performance.

Hippocampal Ablation in Rats: Effects of Intertrial Interval

DEFICITS in recent memory following damage to the hippocampus have been reported in man1 and in the monkey2. In a recent investigation3, we tested the hypothesis that the hippocampus is involved in recent memory functions by using different intertrial intervals in runway acquisition and extinction. The method consisted of administering acquisition and extinction trials to rats under either massed or distributed practice conditions. It was found that the temporal spacing of trials during acquisition was not important but that distributed practice trials served to increase resistance to extinction for hippo-campal-damaged rats. The purpose of the work reported here was to clarify the earlier results by determining whether the extinction phenomenon was due to the spacing of trials during acquisition or during extinction. In this work, each subject received both massed and distributed trials during acquisition so that, by the end of this phase of training, all subjects had equal experience with each of the two intertrial intervals. At that time the subjects were extinguished under either massed or distributed practice conditions.

EMOTIONALITY CHANGES FOLLOWING SEPTAL AND NEOCORTICAL ABLATIONS IN RATS.

EMOTIONALITY CHANGES FOLLOWING SEPTAL AND NEOCORTICAL ABLATIONS IN RATS.

Basal tegmental self-stimulation after septal ablation in rats.

Olds⁸showed that stimulation of one of many areas of the brain could be used as a "reward" to maintain bar pressing and other behavior. Except for the amygdala, the areas most effective in sustaining high rates of responding were near the midline and extended continuously from the basal tegmentum through the hypothalamus and preoptic areas to the septum. The neurological basis for the "rewarding" effects elicited from these areas remains unknown. Several lines of evidence suggest that activity in some portion or portions of the rhinencephalon is involved in sustained self-stimulation behavior. MacLean and co-workers^6,7have reported that septal or hippocampal stimulation may result in hippocampal seizure activity, which is followed by a period of electrical after-discharge. Behaviorally these animals show an immobilization phenomenon described as "catatonic-like" during the seizure itself, and "enhanced grooming" and "enhanced pleasure" reactions during the period of the after-discharge. That such a

Test of the abstract attitude in chimpanzees following ablation of prefrontal cortex.

LASHLEY 1 demonstrated that the deficit in learning and retention following cortical ablations in rats is a function of the amount of tissue removed, rather than of the locus of such removals. The search for regional specialization of function in the cortex of higher mammals, however, has continued, encouraged, no doubt, by the notion of increasing corticalization in evolutionary development. To the prefrontal areas of the cortex are usually assigned the function of mediating higher mental processes, characteristic of the primates, and especially of man. These processes are usually hazily specified, with vague references to inferential thinking, symbolism, mental synthesis, and the like. There have been various attempts, however, to define the function of the frontal lobes more exactly, usually by assigning to them some basic process which enters into a variety of intelligent performances. Thus, Jacobsen 2 suggested that they are essential for the immediate memory which underlies solution