Posttraining estradiol injections enhance memory in ovariectomized rats: cholinergic blockade and synergism

Three models (independent, interdependent, and mediational) were hypothesized in this study, to examine the interrelation of personality, family, and peer determinants and their effects on tobacco use by young adults. Mothers were first interviewed about their children when they were between the ages of 1 and 10 years old. Three subsequent interviews were conducted with the children when they reached adolescence and young adulthood. Results show support for the mediational model. In accordance with family interactional framework conceptions, there was a sequence in patterning: from parenting during early adolescence; to personality and peer factors, extending to smoking in late adolescence; and culminating in smoking in adulthood. With a developmental approach, a number of psychosocial measures were related in both younger and older children. Nevertheless, some interesting developmental differences emerged. The findings suggest at least four possible targets for therapeutic or preventive intervention: the parent, the child, the adolescent, and the peer group.     

Suppression of kindling epileptogenesis in rats by intrahippocampal cholinergic grafts

The objective of our study was to investigate the effects of ultrasonic energy on tissues, using a porcine model, performed under various instrumental and procedural parameters. Domestic pigs were anesthetized and prepared for surgery. An incision was made on the side of the hip randomly assigned to the right or left side. Tumescence solution was infiltrated via a blunt tip, small diameter cannula, followed by performance of standard liposuction. On the contralateral side, a similar incision was made. For ultrasonic liposuction experiments without the sheath, a percutaneous introducer was inserted into the incision, which was protected at the entry site from contact with the cannula. Tumescence solution was infiltrated via a blunt tip, small diameter cannula, and then the site was treated with ultrasonic energy at maximum output from the machine with liposuction concurrent through the hollow cannula. The experiments with the sheath did not require a pretreatment with tumescence solution but consisted of tumescence solution pumped through the sheath at a low infusion rate, with concurrent treatment utilizing ultrasonically assisted liposuction through the central lumen of the cannula. In all cases, the lipoaspirate was preserved for biochemical analysis. After treatment, the pigs were euthanized, and samples for histopathology were taken. The pigs were then perfused with a radio-opaque solution through the left ventricle following preperfusion with saline. The groups were ultrasound-assisted liposuction with sheath (n = 3), ultrasound-assisted without sheath (n = 4), and tumescence alone (n = 1), with standard liposuction performed on the contralateral side for all ultrasound-assisted liposuction animals. The lipoaspirates from the ultrasonically assisted liposuction with the sheath showed significantly less blood loss (measured as hemoglobin in the aspirate) than standard liposuction (p = 0.012) at comparable levels of fat (measured as triglycerides in the aspirate). The lipoaspirates from ultrasound-assisted liposuction without the sheath showed blood loss comparable to that experienced with standard liposuction. The ratio of hemoglobin to triglyceride was lowest in the ultrasound-assisted group with (p = 0.01) and without (p = 0.06) the sheath when compared to traditional liposuction. In both of these treated groups, the radiograms of the perfused areas showed significantly less vascular disruption when compared with suction-assisted liposuction. Histopathologic examination of specimens taken from various treated areas showed substantial tissue damage comparable in ultrasound- and suction-assisted liposuction treated groups. This preliminary experimental study showed that ultrasound-assisted lipoplasty is comparable to traditional suction-assisted lipoplasty. Treatment with ultrasound provided more significant hemoglobin/triglyceride ratios, indicative of more lipid aspirated per hemoglobin lost, and better preservation of vascular tissues as demonstrated by our perfusion studies. Treatment with the sheath showed a significantly lower hemoglobin release with a diminished volume infused into the subcutaneous space during the procedure.     

Intracerebroventricular insulin improves spatial learning and memory in male Wistar rats.

As one of the most studied protein hormones, insulin as well as its receptor have been known to play key roles in a variety of important biological processes. Detection of insulin and its receptor in the central nervous system (CNS) has led to a rapidly growing interest in the central effects of insulin. Insulin and its receptor are located in the specific area of the CNS with a diversity of region-specific functions different from its direct carbohydrate homeostasis in the periphery. The high density of insulin/insulin receptor in brain areas such as the hippocampus and cerebral cortex have shown to play an important role in higher cognitive functions, suggesting that insulin might be involved in the modulation of memory. Previous studies have offered controversial results regarding the effects of insulin on various types of memory. The aim of the present study is to determine whether intracerebroventricular (ICV) administration of insulin improves the water maze performance of rats. The experimental groups had pretraining insulin infusion (2, 4, 8, 16, and 32 mu) into the third ventricle, and then they were compared with a sham (saline) group. Insulin treatment caused an enhancing effect on spatial memory in a dose-dependent manner. The low doses (2, 4, and 8 mu) of insulin had no significant effect on the water maze achievement of rats, whereas higher doses (16 and 32 mu) significantly improved the rats’ performance. These results suggest that ICV administration of insulin may result in a dose-dependent improvement of memory function in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intra-hippocampal estradiol infusion enhances memory in ovariectomized rats

Ovariectomized adult Long-Evans rats received an eight-trial training session in a hippocampal-dependent hidden platform water maze task. Following trial 8, rats received an intra-hippocampal injection of estradiol in a water soluble cyclodextrin inclusion complex (1.0, 2.0 or 5.0 micrograms/0.5 microliter), or saline. Twenty-four hours later, the retention test escape latencies of rats administered post-training intra-hippocampal injections of estradiol (5.0 micrograms) were significantly lower than those of saline treated rats, indicating a memory-enhancing effect of estradiol. Injections of estradiol (5.0 micrograms) given 2 h post-training had no effect on retention, indicating a time-dependent effect of estradiol on memory storage processes.     

Posttraining paradoxical sleep in rats is increased after spatial learning in the Morris water maze.

The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris water maze was evaluated. Sprague-Dawley rats were given a 12-trial training session in either the hidden or the visible platform versions of the task. Subgroups then underwent paradoxical sleep deprivation (PSD) beginning at different times after training. Rats with PSD imposed from 14 hr after spatial training had poorer retest scores than any other group. Other rats, implanted with electrodes to permit continuous recording of sleep electroencephalography, were found to undergo a prolonged period of elevated PS after spatial training. By contrast, rats trained in the nonspatial version of the water maze task did not show retention deficits after PSD or elevated PS after training. These results support a role for PS in spatial, but not nonspatial, learning in the Morris water maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain transplants enhance rather than reduce the impairment of spatial memory and olfaction in bulbectomized rats.

The possibility to compensate the loss of olfactory and non-olfactory functions due to removal of the olfactory bulb by embryonal brain grafts was investigated in adult rats. Spatial working memory was examined in an 8-arm radial water maze task 6 weeks after bulbectomy. During 15 daily trials, performance gradually improved in bulbectomized controls (n?=?10) and in rats with olfactory bulb transplants (n?=?9), but did not attain that of intact controls (n?=?10). No improvement was observed in the rats with substantia nigra grafts (n?=?8). 11 wks after bulbectomy, the same rats were tested in the water tank navigation task. The performance improved during ten 12-trial sessions in bulbectomized rats less than in intact controls, but more than in the transplanted rats. The olfactory food retrieval test performed 14 wks after bulbectomy revealed almost full recovery of smell in bulbectomized rats, but not in the transplanted animals. It is concluded that the spatial memory deficit is probably due to bulbectomy-induced interference with septohippocampal function which is not alleviated, but rather enhanced by transplantation. Results suggest that the effect of brain grafting is not always beneficial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of cholinergic system in losartan-induced facilitation of spatial and short-term working memory

In the present study we have shown the potential memory enhancing property of losartan, a selective Ang II AT1 receptor antagonist. Nootropic activity of losartan in mice was assessed by using passive avoidance step-down task and elevated plus-maze as a measure of short-term working and spatial memory respectively. Losartan at higher dose (10 mg/kg i.p) improved the basal performance in retention testing in both the test paradigms. Prior administration of losartan also attenuated retention deficit induced by scopolamine (0.3 mg/kg i.p). Moreover, physostigmine (0.05 mg/kg i.p) potentiated memory enhancing properties of losartan administered at lower dose (5 mg/kg i.p). On the basis of above observations it is concluded that the memory enhancing properties of losartan can be attributed to increased cholinergic activity.     

Interactions between 192-IgG saporin and intraseptal cholinergic and GABAergic drugs: Role of cholinergic medial septal neurons in spatial working memory.

Rats were administered 192-IgG saporin (SAP) or vehicle into the medial septum-vertical limb of the diagonal band (MS-vDB). Starting 1 week later, the effects of intraseptal scopolamine, oxotremorine, and muscimol were tested in a T-maze alternation task. Choice accuracy in the absence of infusions did not differ between control and SAP-treated rats. Intraseptal scopolamine or muscimol impaired the choice accuracy of SAP-treated but not control rats. Oxotremorine impaired accuracy similarly in control and SAP-treated rats. The enhanced effects of scopolamine and muscimol produced by SAP are consistent with the hypothesis that cholinergic MS-vDB neurons are used in spatial working memory. The finding that SAP alone did not alter choice accuracy provides further evidence that cholinergic MS-vDB neurons are not necessary for spatial working memory. Thus, cholinergic MS-vDB neurons are involved in but not necessary for spatial working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurotransmitters and memory: Role of cholinergic, serotonergic, and noradrenergic systems.

In Alzheimer's disease (AD), pathological changes are found in the basal forebrain cholinergic system (BFCS), serotonergic raphe (RA), and noradrenergic locus coeruleus (LC) systems. The present study examined the extent to which selective damage in each of these systems individually could produce an impairment of memory, one of the clinical symptoms of AD. Rats were given selective lesions by injecting ibotenic acid into the nucleus basalis magnocellularis and medial septal area (i.e., BFCS); 5,7-dihydroxytryptamine into the medial and dorsal RA; and 6-hydroxydopamine (6-OHDA) into the LC or by ip injections of (2-chloroethyl)N-ethyl-2-bromobenzylamine HCl (DSP4). Rats were tested in a delayed spatial alternation in a T-maze. BFCS lesions impaired choice accuracy with intertrial delays of 5, 30, and 60 s. RA lesions or DSP4 injections impaired choice accuracy only when the intertrial delay was 60 s. LC lesions (by 6-OHDA) did not impair choice accuracy at any delay. The results suggest that the pathological changes in the BFCS and RA are sufficient to produce the types of memory impairments associated with dementia, but the quantitative effects of pathology in these two systems are different. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Remembrance of places you passed: Social spatial working memory in rats.

Pairs of rats were tested in a radial-arm maze to determine whether the spatial choices made by one rat affect the subsequent spatial choices of the other rat. In a free-choice procedure, rats showed an increased tendency to choose the location that had most recently been chosen by a foraging partner but a decreased tendency to visit locations that the foraging partner had visited earlier. Forced-choice procedures were used to better control the social stimulus and the interactions between the rats. Under some conditions, locations were chosen later in the choice sequence of a subject rat if another rat had been observed choosing that location. Odor and other physical traces of the other rat's visits were ruled out as explanations for this effect. The results demonstrate the existence of working memory for locations visited by a familiar conspecific. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of retroactive interference in the spatial memory of normal rats and rats with hippocampal lesions.

Studied the importance of retroactive interference (RI) in memory for spatial locations by using a 12-arm radial maze and a standard RI paradigm. 26 male albino Sprague-Dawley rats in the RI condition first learned to choose 4 of the 12 arms, followed by training to a 2nd set of 4 arms. In the control condition for interference, Ss learned the 1st set of arms but were not trained to approach the 2nd set. Thereafter, Ss in each interference condition were assigned to groups (hippocampal, cortical control, or unoperated control), the operations were carried out, and then all Ss were tested for retention of the set of arms learned first. Contrary to predictions of the cognitive map theory (J. O'Keefe and L. Nadel, 1978), RI was found in control Ss. The severe memory deficit found in hippocampals was not influenced by the interference variable. In addition to impaired performance early in relearning, Ss with hippocampal lesions continued to make many errors throughout the 10 wks of testing, including choices to unbaited arms and repeated entries into baited arms. However, hippocampals eventually learned not to reenter unbaited arms. Data indicate a deficit in the selection and utilization of sets of responses and are interpreted as implicating the hippocampus in retrieval processes. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficits of spatial learning and working memory in spontaneously hypertensive rats

It is possible that behavioral dysfunction, including cognitive, perceptual and psychomotor impairments in hypertensive subjects, can be the result of the high blood pressure. The aim of this study was to evaluate the performance of the spontaneously hypertensive rats (SHR) in the acquisition and execution of tasks in an 8-arm radial maze. Male Wistar normotensive rats (CON, n = 11) and SHR (n = 12), 3 months old, were first submitted to a series of training sessions to enter each of the 8 arms once in a given session (task acquisition), and errors (revisiting an arm in the same session) were computed. Errors before and after two delay intervals (5 s and 1 h, introduced between the fourth and fifth arm choice) were measured. These delayed tests allowed us to evaluate the working memory in different terms. It was observed that the SHR group made slightly more errors during the acquisition sessions and in the execution of the post-delay of 5-s interval tests, and significantly in the execution of the post-delay of 1-h interval tests compared to the CON. These results show that the SHR has a deficiency in the performance of the radial maze, suggestive of impairment of learning and working memory, mainly for a long-term memory, corroborating the hypothesis about the possible behavioral consequences of hypertension.     

Selective immunotoxic lesions of basal forebrain cholinergic cells: Effects on learning and memory in rats.

Male Long-Evans rats were given injections of either 192 IgG-saporin, an apparently selective toxin for basal forebrain cholinergic neurons (LES), or vehicle (CON) into either the medial septum and vertical limb of the diagonal band (MS/VDB) or bilaterally into the nucleus basalis magnocellularis and substantia innominata (nBM/SI). Place discrimination in the Morris water maze assessed spatial learning, and a trial-unique matching-to-place task in the water maze assessed memory for place information over varying delays. MS/VDB-LES and nBM/SI-LES rats were not impaired relative to CON rats in acquisition of the place discrimination, but were mildly impaired relative to CON rats in performance of the memory task even at the shortest delay, suggesting a nonmnemonic deficit. These results contrast with effects of less selective lesions, which have been taken to support a role for basal forebrain cholinergic neurons in learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemosensory and hormonal mediation of social memory in male rats.

The persistence with which 12 intact and 12 castrated adult male Holtzman rats investigated a juvenile conspecific was reduced following preexposure to either the juvenile or chemosensory stimuli (soiled bedding or urine) from that juvenile, which suggests the presence of a chemosensorily mediated social memory. Any such memory may have adaptive value in that it permits a more ready identification of novel conspecifics. Persistence of social investigatory behavior in castrated Ss demonstrates the importance of male gonadal hormones in the chemosensorily mediated social memory. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testosterone increases and estradiol decreases middle cerebral artery occlusion lesion size in male rats

This study was undertaken to determine the effects of estrogen and testosterone on cerebral ischemic lesion size induced by middle cerebral artery (MCA) occlusion in male rats. Rats were gonadectomized and treated with testosterone, estrogen, or testosterone plus estrogen filled Silastic pellets. The animals were divided into 6 groups: intact, intact + estrogen (E2), castrate, castrate + testosterone (T), castrate + E2, and castrate + T + E2. One week after treatment, cerebral ischemia was induced by MCA occlusion for 40 min, followed by reperfusion. After 24 h, rats were sacrificed and slices were then stained to assess lesion size. The presence of testosterone increased and the removal of testosterone decreased lesion size. A strong positive correlation (r2 = 0.922) between plasma testosterone concentrations and ischemic lesion size was observed. Estradiol treatment reduced ischemic area. In summary, the present study provides evidence that testosterone exacerbates and estrogens ameliorate ischemic brain damage in an animal model of cerebral ischemia.     

Redistribution of spatial representation in the hippocampus of aged rats performing a spatial memory task.

Young and old rats performed on a maze according to a forced-choice and then a spatial memory procedure either in the same or a different environment. Aged rats were slower to learn the spatial memory task when tested in the same, but not in a different, room. One interpretation of this pattern of results is that although old rats learn new rules as quickly as young rats, they show less flexibility with old rules and familiar spatial information. Impaired choice accuracy during asymptote performance suggests poor processing of trial-unique information by old rats. Spatial correlates of hippocampal CA1 and hilar cells varied with task demand: CA1 cells of aged rats showed more spatially selective place fields, whereas hilar cells showed more diffuse location coding during spatial memory, and not forced-choice, tests. Such representational reorganization may reflect a compensatory response to age-related neurobiological changes in the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttraining electrical stimulation of vagal afferents with concomitant vagal efferent inactivation enhances memory storage processes in the rat

Peripherally administered or released substances that modulate memory storage, but do not freely enter the brain, may produce their effects on memory by activating peripheral receptors that send messages centrally through the vagus nerve. Indeed, vagus nerve stimulation enhances memory performance, although it is unclear whether this effect is due to the activation of vagal afferents or efferents. To eliminate the possible influence of descending fibers on memory storage processes, rats were implanted with cuff electrode/catheter systems along the left cervical vagus. Forty-eight hours following surgery, each animal received a 3. 0-microliter infusion (1.0 microliter/min) of either lidocaine hydrochloride (75.0 mM) or isotonic saline below the point of stimulation. Animals were then trained 10 min later on an inhibitory-avoidance task with a 0.75-mA, 1.0-s foot shock. Sham stimulation or vagus nerve stimulation (0.5-ms biphasic pulses; 20.0 Hz; 30 s; 0.2, 0.4, or 0.8 mA) was administered immediately after training. Memory, tested 24 h later, was enhanced by stimulation whether descending vagus nerve fibers were inactivated or not. Both lidocaine- and saline-infused groups showed an intensity-dependent, inverted-U-shaped pattern of retention performance, with the greatest effect observed for 0.4 mA (U = 9, p < .05, and U = 7, p < .01, respectively). Additionally, animals that received lidocaine infusions, but no vagus nerve stimulation, showed impaired memory compared to the performance of saline-infused control animals (U = 11, p < .05). Together, these findings suggest that vagal afferents carry messages about peripheral states that lead to the modulation of memory storage and that the memory-enhancing effect produced by vagus nerve stimulation is not mediated via the activation of vagal efferents.     

Partial hippocampal inactivation: Effects on spatial memory performance in aged and young rats.

Changes in anatomical or functional connectivity during normal aging are thought to contribute to cognitive alterations over the lifespan. Neural network theories predict that synaptic loss in an aging brain could place the organism near the point of dysfunction in the nonlinear curve defining neural compromise versus performance. The present experiments examined whether aged rats are closer to this point of behavioral dysfunction by reversibly inactivating one or both hippocampal hemispheres. As expected, bilateral tetracaine inactivation of the hippocampus disrupted spatial memory in both age groups. Unilateral left hippocampal inactivation significantly increased errors only in aged rats; however, unilateral inactivation of the right hippocampus had no effect. The present outcome could reflect more extensive synaptic dysfunction in the aged right hippocampus or a greater involvement of the left hippocampus in spatial working memory problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)