High density of benzodiazepine binding sites in the substantia innominata of the rat

PWZ-029, an inverse agonist selective for α₅ GABAA receptors, improves object recognition, but not water-maze memory in normal and scopolamine-treated rats

Inverse agonism at the benzodiazepine site of α(5) subunit-containing GABA(A) receptors is an attractive approach for the development of putative cognition-enhancing compounds, which are still far from clinical application. Several ligands with binding and/or functional selectivity for α(5) GABA(A) receptors have been synthesized and tested in a few animal models. PWZ-029 is an α(5) GABA(A) selective inverse agonist whose memory enhancing effects were demonstrated in the passive avoidance task in rats and in Pavlovian fear conditioning in mice. In the present study we investigated the effects of PWZ-029 administration in novel object recognition test and Morris water maze, in normal and scopolamine-treated rats. All the three doses of PWZ-029 (2, 5 and 10 mg/kg) improved object recognition after the 24-h delay period, as shown by significant differences between the exploration times of the novel and old object, and the respective discrimination indices. PWZ-029 (2 mg/kg) also successfully reversed the 0.3 mg/kg scopolamine-induced deficit in recognition memory after the 1-h delay. In the Morris water maze test, PWZ-029 (5, 10 and 15 mg/kg) did not significantly influence swim patterns, either during five acquisition days or during the treatment-free probe trial. PWZ-029 (2, 5 and 10 mg/kg) also proved to be ineffective in the reversal of the 1mg/kg scopolamine-induced memory impairment in the water maze. The present mixed results encourage use of a variety of tests and experimental conditions in order to increase the predictability of preclinical testing of selective α(5) GABA(A) inverse agonists.

Projections from the nociceptive area of the central nucleus of the amygdala to the forebrain: a PHA-L study in the rat

The lateral capsular division (CeLC) of the central nucleus (Ce) of the amygdala, in the rat, has been shown to be the main terminal area of a spino(trigemino)-parabrachio-amygdaloid nociceptive pathway [Bernard & Besson (1990) J. Neurophysiol. 63, 473-490; Bernard et al. (1992) J. Neurophysiol. 68, 551-569; Bernard et al. (1993) J. Comp. Neurol. 329, 201-229]. The projections to the forebrain from the CeLC and adjacent regions were studied in the rat by using microinjections of Phaseolus vulgaris leucoagglutinin (PHA-L) restricted in subdivisions of the Ce and the basolateral amygdaloid nucleus anterior (BLA). Our data showed that the entire CeLC projects primarily and extensively to the substantia innominata dorsalis (SId). The terminal labelling is especially dense in the caudal aspect of the SId. The other projections of the CeLC in the forebrain were dramatically less dense. They terminate in the bed nucleus of the stria terminalis (BST) and the posterior hypothalamus (pLH). No (or only scarce) other projections were found in the remaining forebrain areas. The Ce lateral division (CeL) and the Ce medial division (CeM), adjacent to the CeLC, also project to the SId with slightly lower density labelling. However, contrary to the case of the CeLC, both the CeL and the CeM extensively project to the ventrolateral subnucleus of the BST (BSTvl) with a few additional terminals found in other regions of the lateral BST. Only the CeM projects densely to both the interstitial nucleus of the posterior limb of the anterior commissure and the caudal most portion of the pLH. The projections of the BLA are totally different from those of the Ce as they terminate in the dorsal striatum, the accumbens nucleus, the olfactory tubercle, the nucleus of olfactory tract and the rostral pole of the cingulate/frontal cortex. This study demonstrates that the major output of the nociceptive spino(trigemino)-parabrachio-CeLC pathway is to the SId. It is suggested that the CeLC-SId pathway could have an important role in anxiety, aversion and genesis of fear in response to noxious stimuli.

Effects of ZK 93426 on muscarinic and nicotinic antagonist or nucleus basalis lesioning-induced electrocortical slowing

The present study investigated the effects of a benzodiazepine receptor antagonist, beta-carboline ZK 93426 (1, 3 and 10 mg/kg, IP), on scopolamine and nucleus basalis (NB) quisqualic acid lesion-induced neocortical electrocortical activity slowing in rats. Scopolamine induced a dose dependent increase in EEG spectral values and slow delta waves (0.3 < 0.9 = 2.7 mg/kg IP). ZK 93426 partially reversed EEG slowing induced by the smallest scopolamine dose (0.3 mg/kg), but had no effect on the EEG changes induced by higher doses. A combination of scopolamine at 0.3 mg/kg and mecamylamine (a centrally active nicotinic antagonist) at 10 mg/kg induced an EEG slowing that was not reversed by ZK 93426. NB lesions markedly decreased cortical choline acetyltransferase (ChAT) activity (-77%) and increased EEG slow waves. ZK 93426 had no effect on the NB lesion-induced slow wave activity increase. The present results support the idea that beta-carboline ZK 93426 may increase cortical cholinergic activity by disinhibiting the NB cholinergic neurons. However, if the activity of "NB to cortex" cholinergic system is greatly decreased by either a marked reduction in NB cell number (in NB-lesioned rats), a near complete cortical post-synaptic muscarinic receptor blockade (large scopolamine dose) or by a combination of nicotinic (decrease acetylcholine release) and muscarinic receptor blockade, the effects of beta-carboline ZK 93426 on EEG slowing may be negligible.

Intra-accumbens infusions of antisense oligodeoxynucleotides to one isoform of glutamic acid decarboxylase mRNA, GAD65, but not to GAD67 mRNA, impairs sustained attention performance in the rat

The effects of bilateral infusions of antisense oligodeoxynucleotides (ODNs) for the two isoforms of glutamic acid decarboxylase (GAD65; GAD67) into the nucleus accumbens on the performance of intact rats in a task designed to assess sustained attention were tested. The task required the animals to discriminate between signal and non-signal events. Signals and non-signals were presented randomly and unpredictably. The task generated all four response types of a sustained attention task, i.e., hits, misses, correct rejections, false alarms. Infusions of the scrambled sequence ODNs did not affect performance. Likewise, infusions of the GAD67 ODNs failed to produce any effect. However, infusions of the GAD65 ODNs into the nucleus accumbens resulted in a robust and reliable decrease in the relative number of hits. Similarly, the combined infusion of GAD65+67 ODNs impaired the hit rate but did not affect the animals' ability to reject non-signals. Following each treatment series, performance rapidly returned to baseline, further indicating the specificity and reversibility of the effects of the infusions of the ODNs. While these data suggest that translation arrest of specifically the GAD65 isoform of the enzyme in the nucleus accumbens impairs attentional performance, the neuronal mechanisms mediating these effects remain unsettled.

Anxiolytic-like action of neurokinin substance P administered systemically or into the nucleus basalis magnocellularis region

There is evidence that the neurokinin substance P plays a role in neural mechanisms governing learning and reinforcement. Reinforcing and memory-promoting effects of substance P were found after it was injected into several parts of the brain and intraperitoneally. With regard to the close link between anxiety and memory processes for negative reinforcement learning, the aim of the present study was to gauge the effect of substance P on anxiety-related behaviors in the rat elevated plus-maze and social interaction test. Substance P was tested at injection sites where the neurokinin has been shown to promote learning and to serve as a reinforcer, namely in the periphery (after i.p. administration) and after injection into the nucleus basalis magnocellularis region. When administered i.p., substance P had a biphasic dose-response effect on behavior in the plus-maze with an anxiolytic-like action at 50 microg/kg and an anxiogenic-like one at 500 microg/kg. After unilateral microinjection into the nucleus basalis magnocellularis region, substance P (1 ng) was found to exert anxiolytic-like effects, because substance P-treated rats spent more time on the open arms of the plus-maze and showed an increase in time spent in social interaction. Furthermore, the anxiolytic effects of intrabasalis substance P were sequence-specific since injection of a compound with the inverse amino acid sequence of substance P (0.1 to 100 ng) did not influence anxiety parameters. These results show that substance P has anxiolytic-like properties in addition to its known promnestic and reinforcing effects, supporting the hypothesis of a close relationship between anxiety, memory and reinforcement processes.

Effects of S-8510, a novel benzodiazepine receptor partial inverse agonist, on basal forebrain lesioning-induced dysfunction in rats

We investigated the effects of a novel benzodiazepine partial inverse agonist, S-8510 (2-(3-isoxazolyl)-3,6,7,9-tetrahydroimidazo [4,5-d] pyrano [4,3-b] pyridine monophosphate monohydrate), on the impairment of spatial memory, decreased high-affinity choline uptake and acetylcholine release in basal forebrain-lesioned rats. S-8510 (3 and 5 mg/kg, p.o. 30 min before each training session) significantly ameliorated the basal forebrain-lesion-induced impairment of spatial memory in water maze task. In vivo brain microdialysis studies showed that systemic administration of S-8510 at 3 and 10 mg/kg significantly increased the release of acetylcholine in the front-parietal cortex in basal forebrain-lesioned rats. Further, repeated administration of S-8510 (3 and 10 mg kg(-1) day(-1) for 5 days) reversed the decrease in cortical high-affinity choline uptake induced by basal forebrain lesion. Thus, S-8510 improved the spatial memory impairment induced by lesion of the basal forebrain in rats. In addition, it increased acetylcholine release and high-affinity choline uptake from the cortex, a region closely associated with memory, in basal forebrain-lesioned rats. These results indicate that S-8510 has cognition enhancing and cholinergic-activating effects in the basal forebrain-lesioned rats, suggesting that this agent may be useful for the treatment of mild to moderate senile dementia including Alzheimer's disease.

Trans-synaptic stimulation of cortical acetylcholine and enhancement of attentional functions: a rational approach for the development of cognition enhancers

Activation and restoration of cholinergic function remain major foci in the development of pharmacological approaches toward the treatment of cognitive dysfunctions associated with aging and dementia. Our research has been guided by the hypothesis that (re)activation of cortical cholinergic inputs is achieved as a result of trans-synaptic disinhibition of basal forebrain cholinergic neurons. This approach depends on the ability of benzodiazepine receptor (BZR) inverse agonists to reduce the potency of GABA to block neuronal excitation. BZR inverse agonists were found to augment cortical ACh efflux through interaction with cognition-associated activation of this system. Cortical cholinergic inputs have been implicated in the processing of behaviorally significant stimuli, i.e., attentional functions. Using a recently developed and validated task for the measurement of sustained attention, or vigilance, administration of BZR inverse agonists were found to selectively increase the number of false alarms in intact animals. However, in animals with a 50-70%, but not > 90%, loss of the cortical cholinergic inputs, treatment with BZR inverse agonists alleviated the lesion-induced impairment in sustained attention and enhanced activated cortical ACh efflux. A rational development of cognitive enhancers will benefit from experiments in which cognitive and neuropharmacological variables are assessed simultaneously, thus allowing the analysis of interactions between cognition-associated neuronal activity and the neuronal and cognitive effects of putative cognition enhancers.

Stimulation of cortical acetylcholine efflux by FG 7142 measured with repeated microdialysis sampling

The effects of the benzodiazepine receptor partial inverse agonist beta-carboline FG 7142 on cortical ACh efflux were determined using in vivo microdialysis in freely-moving rats. Additionally, a within-subjects, repeated-dialysis experimental design (four microdialysis sessions; removable dialysis probe) was evaluated as a method for measuring changes in basal and FG 7142-stimulated ACh efflux in the frontoparietal cortex. FG 7142 (4.0, 8.0, and 16.0 mg/kg) produced a 150-470% increase in cortical ACh efflux, with a dose-dependent effect on the duration of the increase in efflux. Basal cortical ACh efflux was lower in session 4 than in session 1. However, the ability of FG 7142 to stimulate efflux was unchanged by repeated dialysis testing. The ability of tetrodotoxin (1.0 microM) to suppress both basal and FG 7142-stimulated ACh efflux was also unaffected by repeated dialysis testing. These results demonstrate that systemically administered benzodiazepine receptor inverse agonists stimulate cortical ACh efflux, and that repeated-measures experimental designs can be valid for determining certain changes in cortical ACh efflux with in vivo microdialysis.

Bidirectional modulation of cortical acetylcholine efflux by infusion of benzodiazepine receptor ligands into the basal forebrain

In a previous in vivo microdialysis study in rats, it was found that cortical acetylcholine (ACh) efflux was reliably increased by a multimodal appetitive stimulus (onset of darkness with presentation of palatable food). Furthermore, this stimulated ACh efflux was significantly enhanced by systemic administration of a benzodiazepine receptor (BZR) weak inverse agonist and significantly reduced by a BZR full agonist. These effects contrasted with the minimal effects of BZR ligands on basal cortical ACh efflux in resting animals. The aim of the present study was to determine whether this modulation of stimulated cortical ACh efflux by BZR ligands was mediated within the basal forebrain. ACh efflux, measured with in vivo microdialysis, was stimulated by onset of darkness, an event which predicted delivery of palatable food. The BZR full inverse agonist, beta -CCM (3.0 micrograms/hemisphere) or the full agonist chlordiazepoxide (40.0 micrograms/hemisphere) was infused into the basal forebrain just prior to the darkness/food stimulus. Similar to previous results with systemic administration, the BZR full inverse agonist enhanced, while the full agonist reduced, stimulated cortical ACh efflux. These results demonstrate that the action of BZR ligands in the basal forebrain is sufficient for their modulation of cortical ACh release.

Prenatal oxazepam affects passive avoidance performance of preweaning mice

CD-1 outbred mice were exposed to oxazepam on fetal days 12-16 by maternal administration (per os of 15 mg/kg twice daily at 8 a.m. and 8 p.m.) and fostered at birth to untreated dams, while control mice received vehicle solution. Mice were then tested on postnatal day 14 and 15 in a passive avoidance apparatus for their ability to withhold a step-down response from a vibrating platform. The step-down response was punished with a mild footshock. Each animal was subjected to a maximum of 15 trials. Mice prenatally treated with oxazepam showed an impairment in the acquisition of the task as indicated by shorter latencies to step-down throughout the 15 trials in both sessions (days 14 and 15). As control nonreinforced animals prenatally treated with oxazepam did not show a similar alteration in latency to step-down, these data suggest that prenatal exposure to oxazepam influences behavioral performance of preweaning mice in an aversively motivated task.

Effects of intracranial infusions of chlordiazepoxide on spatial learning in the Morris water maze. I. Neuroanatomical specificity

The present investigation sought to determine the neuroanatomical locus through which the amnesic and anxiolytic effects of the benzodiazepine agonist chlordiazepoxide are mediated. Rats were infused with either chlordiazepoxide (60 nmol/microliters) or artificial CSF (1 microliter) into either the frontal cortex, nucleus basalis magnocellularis/substantia innominata, amygdala, medial septum, hippocampus, or cerebellum and run in the open field to assess anxiety as thigmotaxia and in the Morris water maze to assess spatial learning. Other rats were given chlordiazepoxide (5 mg/kg) or saline (1 ml/kg) systemically and run in the open field and water maze. When chlordiazepoxide was administered systemically, rats showed significantly less thigmotaxia, but not overall activity, than controls in the open field, and were deficit in spatial learning, but not cue learning or swim speed, in the water maze. Intracranial infusions revealed a neuroanatomical specificity for the amnesic and anxiolytic actions of chlordiazepoxide. Infusions of chlordiazepoxide into the amygdala, but none of the other structures, reduced thigmotaxia without affecting overall activity levels whereas infusions into the medial septum, but none of the other structures, prevented spatial learning, but not cue learning, and reduced swim speed in the water maze. Together, these finding suggest that the medial septum and the amygdala mediate the amnesic and anxiolytic actions of chlordiazepoxide, respectively. Moreover, these results provide direct evidence that the amnesic and anxiolytic actions of chlordiazepoxide are independent.

Effects of an inhibitor of GABA-aminotransferase (gamma-vinyl-GABA) on the spatial navigation deficit induced by nicotinic blockade

1. The present study investigated whether stimulation of the GABA-ergic system affects spatial navigation (water-maze, WM) deficit induced by nicotinic blockade (mecamylamine). 2. The effects of various doses of gamma-vinyl-GABA (GVG: 50, 150 and 300 mg/kg) and mecamylamine (2.5 and 10 mg/kg) were examined alone and in combination. 3. GVG at the dose 150 mg/kg alone did not impair the performance of rats in the WM task. 4. Mecamylamine at the dose 2.5 and 10 mg/kg clearly impaired the performance of rats in WM task. 5. When the two drugs were co-administered, no interaction between mecamylamine and GVG was observed. 6. Combined nicotinic and muscarinic blockade did not interact as well with GVG administration. 7. Our results do not provide support for any interaction between cholinergic and GABA-ergic mechanisms.

Age-dependent modulation of in vivo cortical acetylcholine release by benzodiazepine receptor ligands

In vivo microdialysis was utilized to determine the effects of benzodiazepine receptor (BZR) ligands on cortical acetylcholine (ACh) release in awake young and aged rats. There were no significant differences in baseline cortical ACh release as a function of age. While administration of the BZR selective inverse agonist ZK 93 426 increased ACh release in both groups of animals, the aged rats exhibited a greater stimulation. Unexpectedly, under the present testing conditions, the BZR agonist chlordiazepoxide (CDP) had no systematic effect on ACh release in either group. The presence or absence of these drug effects or drug-age interactions was not secondary to the impact of these compounds on behavioral activity. Cortical ACh release could also be stimulated by turning off the lights in the observation room or by the systemic administration of scopolamine. Aged rats were at least as able as their younger counterparts to respond to these manipulations with increased release. These results suggest that basal and stimulated release of cortical ACh is not impaired at the ages studied. Moreover, selective inverse BZR agonists may be a potent way of trans-synaptically stimulating cortical cholinergic transmission.

Eight-arm maze performance, neophobia, and hippocampal cholinergic alterations after prenatal oxazepam in mice

Outbred CD-1 mice were exposed to oxazepam (15 mg/kg PO twice/day) on days 12-16 of fetal life, i.e., at a critical ontogenetic stage of Type II benzodiazepine (BDZ) receptor increase, and fostered at birth to untreated dams. At adulthood, radial arm maze performance, activity-habituation test in an open-field arena (either single 15-min test or three 5-min sessions at 24-h intervals), approach to a novel stimulus object, and amphetamine or scopolamine effects thereon were assessed in male progeny. Overall, the oxazepam exposed (OX) mice were much less efficient in the radial arm maze task than the vehicle exposed (VEH) animals. Pre-test scopolamine injection, but not amphetamine, significantly impaired the arm maze performance of OX mice when compared with the corresponding VEH-scopolamine animals. In separate nonlearned behavioral tasks, prenatal oxazepam did not affect either baseline activity levels in the open field or the response to the amphetamine and the scopolamine challenge, while it considerably increased the latency of first approach to a novel object and produced a deficit of habituation in the course of the subsequent exploratory period. Concomitant investigation at the neurochemical level showed that the adult OX animals had a significant increase in both Bmax and in the affinity (Kd) of cholinergic muscarinic receptors in the hippocampal formation when compared to the vehicle-exposed controls.

Effects of an inhibitor of GABA-aminotransferase (gamma-vinyl-GABA) on the spatial navigation deficit induced by muscarinic blockade

The present study investigated whether stimulation of the GABAergic system affects spatial navigation [water-maze (WM)] deficit induced by muscarinic blockade (scopolamine). The effects of various doses of gamma-vinyl-GABA (GVG) (50, 150, and 300 mg/kg) and scopolamine (0.4 and 0.1 mg/kg) were examined alone and in combination. GVG at 50 and 150 mg/kg alone did not impair the performance of rats in the WM yask. At 300 mg/kg, GVG caused slight impairment, increasing latency and total distance swim during training trials. Scopolamine at 0.4 mg/kg clearly impaired the performance of rats in the WM task. When the two drugs were coadministered, no interaction between scopolamine and GVG was observed. Our results do not provide support for any interaction between cholinergic muscarinic and GABAergic mechanisms.

Cognitive enhancing properties of beta-CCM infused into the nucleus basalis magnocellularis of the rat

Peripheral administration of various benzodiazepine derivatives or beta-carbolines (inverse agonists at benzodiazepine receptors), has been shown to affect memory. In this study, the effect of local infusion of a beta-carboline-methyl beta carboline-3-carboxylate (beta-CCM) into the nucleus basalis magnocellularis (NBM) of rats was examined in a two-trial recognition task. The results show that beta-CMM (3 micrograms/0.5 microliter) enhances recognition performance when injected both before or immediately after the acquisition trial. These effects appear to be mediated by a benzodiazepine (BZD) receptor since they were blocked by pretreatment with Ro 15-1788, a BZD receptor antagonist. This study supports the involvement of the NBM in cognitive processes, and demonstrates that these processes can be influenced by alteration of GABAergic neurotransmission.

Failure of a chlordiazepoxide to reproduce the behavioral effects of muscimol administered into the basal forebrain

Bilateral infusion of the GABAA-receptor agonist muscimol into the basal forebrain was previously found to impair visual conditional discrimination performance in rats. In order to examine whether the GABAergic input into the basal forebrain is active during performance of this task, the benzodiazepine receptor agonist chlordiazepoxide (15, 25, 40 micrograms/0.5 microliters/hemisphere) was bilaterally infused. Surprisingly, chlordiazepoxide did not affect performance. The impact of this result for the understanding of basal forebrain GABAergic functions is discussed.

GABAergic control of basal forebrain cholinergic neurons and memory

The involvement of the GABAergic innervation of basal forebrain neurons in the rats' conditional visual discrimination performance was examined. Performance in such a task is based on the subjects's ability to retrieve information about response rules, and previous experiments have demonstrated that basal forebrain lesions interfere with this ability. Following the acquisition of the task, chronic guide cannulae were stereotaxically implanted into the substantia innominata of both hemispheres, and the animals were retrained. Administration of the GABAA-agonist muscimol into the substantia innominata (0, 25, 50 ng/0.5 microliters/hemisphere) dose-dependently decreased the number of correct responses, increased the number of errors of omission, increased response latency, but did not affect side bias. Systemic co-administration of the cholinesterase inhibitor physostigmine (0, 0.1, 0.2 mg/kg; i.p.) exclusively interacted with the effects of muscimol on correct responding. Specifically, physostigmine dose-dependently intensified and attenuated the muscimol-induced reduction in correct responding. Although it cannot be excluded that alternative neuronal mechanisms were involved in the mediation of the effects of muscimol and their interaction with physostigmine, these findings support previous evidence indicating that the activity of basal forebrain cholinergic neurons is controlled by a GABAergic input, and that this neuronal link is involved in mnemonic processing.

Elevations of local cerebral glucose utilization by the beta-carboline ZK 93426

The effects of the benzodiazepine receptor antagonist ZR 93,426, a beta-carboline, on local cerebral glucose utilization (LCGU) was examined by using quantitative in-vivo autoradiography with [3H]2-deoxyglucose. ZK 93,426 was found to increase local cerebral glucose utilization primarily in prefrontal, cingulate, olfactory and visual cortical regions, as well as the claustrum, nucleus accumbens, anteroventral thalamus, substantia nigra, and dorsal raphe nucleus. This pattern of changes of LCGU produced by ZK 93,426 seems to represent neither a mirror image of the metabolic effects of benzodiazepine receptor agonists nor the pattern of effects on LCGU induced by the partial inverse agonist beta-carboline FG 7142. The unique pattern of regional changes of glucose utilization induced by ZK 93,426 are discussed with respect to recent findings on its promnestic and antiamnestic properties in animals and humans. It is concluded that ZK 93,426 does not seem to fit into the conventional classification scheme of benzodiazepine receptor ligands; thus, the term 'selective inverse agonist' is proposed.

Activating the damaged basal forebrain cholinergic system: tonic stimulation versus signal amplification

The hypothesis that the cognitive decline in senile dementia is related to the loss of cortical cholinergic afferent projections predicts that pharmacological manipulations of the remaining cholinergic neurons will have therapeutic effects. However, treatment with cholinesterase inhibitors or muscarinic agonists has been, for the most part, largely unproductive. These drugs seem to disrupt the normal patterning of cholinergic transmission and thus may block proper signal processing. An alternative pharmacological strategy which focuses on the amplification of presynaptic activity without disrupting the normal patterning of cholinergic transmission appears to be more promising. Such a strategy may make use of the normal GABAergic innervation of basal forebrain cholinergic neurons in general, and in particular of the inhibitory hyperinnervation of remaining cholinergic neurons which may develop under pathological conditions. Disinhibition of the GABAergic control of cholinergic activity is assumed to intensify presynaptic cortical cholinergic activity and to enhance cognitive processing. Although the extent to which compounds such as the benzodiazepine receptor antagonist beta-carboline ZK 93,426 act via the basal forebrain GABA-cholinergic link is not yet clear, the available data suggest that the beneficial behavioral effects of this compound established in animals and humans are based on indirect cholinomimetic mechanisms. It is proposed that an activation of residual basal forebrain cholinergic neurons can be achieved most physiologically via inhibitory modulation of afferent GABAergic transmission. This modulation may have a therapeutic value in treating behavioral syndromes associated with cortical cholinergic denervation.