Using Nanotechnology to Design Potential Therapies for CNS Regeneration

The nanodelivery of therapeutics into the brain will require a step-change in thinking; overcoming the blood brain barrier is one of the major challenges to any neural therapy. The promise of nanotechnology is that the selective delivery of therapeutics can be delivered through to the brain without causing secondary damage. There are several formidable barriers that must be overcome in order to achieve axonal regeneration after injury in the CNS. The development of new biological materials, in particular biologically compatible scaffolds that can serve as permissive substrates for cell growth, differentiation and biological function is a key area for advancing medical technology. This review focuses on four areas: First, the barriers of delivering therapies to the central nervous system and how nanotechnology can potentially solve them; second, current research in neuro nanomedicine featuring brain repair, brain imaging, nanomachines, protein misfolding diseases, nanosurgery, implanted devices and nanotechnologies for crossing the blood brain barrier; third, health and safety issues and fourth, the future of neuro nanomedicine as it relates to the pharmaceutical industry.

Chronic administration of UMP ameliorates the impairment of hippocampal-dependent memory in impoverished rats

We have previously shown that chronic, but not acute, dietary supplementation with CDP-choline prevents the hippocampal-dependent memory deficits manifested by aged rats and by rats reared under impoverished environmental conditions. In rats, dietary CDP-choline is rapidly metabolized into cytidine and choline; the cytidine is then readily converted to uridine, which enters the brain and, via conversion to UTP and CTP, increases brain levels of membrane phosphatides. Hence, we have assessed whether administering a uridine source (UMP) instead of CDP-choline can also ameliorate the memory deficits in rats reared under impoverished environmental conditions. At weaning, 32 male Sprague-Dawley rats were exposed to either enriched (EC) or impoverished (IC) conditions for 3 mo. Concurrently, IC and EC rats were given access to either a control diet or a diet supplemented with 0.1% UMP. Rats were then assessed for learning and memory skills using 2 versions of the Morris water maze, the hidden platform version that assesses hippocampal-dependent cognitive memory processing, and the visible platform version that assesses striatal-dependent habit memory. As expected, exposure to the impoverished environment impaired hippocampal-dependent, but not striatal-dependent learning and memory. Supplementation with UMP prevented this cognitive dysfunction, as had been observed with supplemental CDP-choline. These results suggest that IC rats do not use and/or remember their spatial strategies for task solving as well as EC rats, and that long-term dietary supplementation with UMP alleviates this dysfunction.

Inhibition of platelet-activating factor receptors in hippocampal plasma membranes attenuates the inflammatory nociceptive response in rats

Evidence suggests that platelet-activating factor (PAF) is a mediator in inflammatory-based pain. Using the biphasic formalin model in rats, we recently demonstrated that PAF antagonists which were selective for either intracellular or plasma membrane PAF receptors decreased the late-phase of the nociceptive response. Inasmuch as both of the PAF antagonists previously used were administered systemically, and reportedly are able to cross the blood-brain barrier, the anatomic locations at which PAF affects pain processing remained to be elucidated. Since PAF is required for hippocampal-dependent memory consolidation, and since the hippocampus has been shown to mediate the late-phase of formalin-induced nociception, the present study investigated the effects on nociception of administration of PAF antagonists within the hippocampus, and of using agents specific for either plasma membrane (BN 52021) or intracellular (BN 50730) PAF binding sites. Intrahippocampal injections of BN 52021 decreased the late-phase of the nociceptive response in a concentration-dependent manner. In contrast, intrahippocampal administration of BN 50730 had no effect on inflammatory nociception. These findings suggest that hippocampal plasma membrane PAF receptors, but not intracellular PAF binding sites, mediate tonic inflammatory pain processing in rats.

Differential induction of c-Jun and Fos-like proteins in rat hippocampus and dorsal striatum after training in two water maze tasks

Research examining the neuroanatomical bases of memory in mammals suggests that the hippocampus and dorsal striatum are parts of independent memory systems that mediate "cognitive" and stimulus-response "habit" memory, respectively. At the molecular level, increasing evidence indicates a role for immediate early gene (IEG) expression in memory formation. The present experiment examined whether acquisition of cognitive and habit memory result in differential patterns of IEG protein product expression in these two brain structures. Adult male Long-Evans rats were trained in either a hippocampal-dependent spatial water maze task, or a dorsal striatal-dependent cued water maze task. Ninety minutes after task acquisition, brains were removed and processed for immunocytochemical procedures, and the number of cells expressing Fos-like immunoreactivity (Fos-like-IR) and c-Jun-IR in sections from the dorsal hippocampus and the dorsal striatum were counted. In the dorsal hippocampus of rats trained in the spatial task, there were significantly more c-Jun-IR pyramidal cells in the CA1 and CA3 regions, relative to rats that had acquired the cued task, yoked controls (free-swim), or naïve (home cage) rats. Relative to rats receiving cued task training and control conditions, increases in Fos-like IR were also observed in the CA1 region of rats trained in the spatial task. In rats that had acquired the cued task, patches of c-Jun-IR were observed in the posteroventral striatum; no such patches were evident in rats trained in the spatial task, yoked-control rats, or naïve rats. The results demonstrate that IEG protein product expression is up-regulated in a task-dependent and brain structure-specific manner shortly after acquisition of cognitive and habit memory tasks.

Dietary CDP-choline supplementation prevents memory impairment caused by impoverished environmental conditions in rats

We previously showed that dietary cytidine (5')-diphosphocholine (CDP-choline) supplementation could protect against the development of memory deficits in aging rats. In the present study, younger rats exposed to impoverished environmental conditions and manifesting hippocampal-dependent memory impairments similar to those observed in the aging rodents were given CDP-choline, and its effects on this cognitive deficit were assessed. Male Sprague-Dawley rats reared for 3 mo in impoverished (IC) or enriched environmental (EC) conditions concurrently received either a control diet or a diet supplemented with CDP-choline (approximately 500 mg/kg/d). After 3 mo, rats were trained to perform spatial and cued versions of the Morris water maze, and their rates of acquisition and retention were compared. Impoverished rats exhibited a selective deficit in hippocampal-dependent spatial memory which could be ameliorated by feeding them CDP-choline. The CDP-choline had no memory-enhancing effect in enriched rats, nor did it prevent the memory impairment of impoverished rats if the animals consumed it for the initial or final months instead of for the entire 3-mo period. These findings indicate that long-term dietary CDP-choline supplementation can ameliorate the hippocampal-dependent memory impairment caused by impoverished environmental conditions in rats, and suggest that its actions result, in part, from a long-term effect such as enhanced membrane phosphatide synthesis, an effect shown to require long-term dietary supplementation with CDP-choline.

Dietary cytidine (5')-diphosphocholine supplementation protects against development of memory deficits in aging rats

The present study was designed to assess the effect of supplementation with dietary cytidine (5')-diphosphocholine (CDP-choline), a source of cytidine and choline, on memory in young and older rats. Although the hippocampal-dependent memory deficits in aged rats are well documented, cognitive functioning in early aging has not been as thoroughly evaluated. Female Sprague-Dawley rats (3 or 15 months of age) consumed either a control diet or a diet supplemented with CDP-choline (approximately 500 mg/kg/day) for 8 weeks, after which they were trained to perform spatial and cued versions of the Morris water maze. Compared with young rats, aged rats exhibited a selective deficit in spatial memory tasks that required rats to retain information for 24 h or longer. CDP-choline supplementation protected against the development of this deficit, but had no memory-enhancing effect in normal young rats. These findings suggest that early-aged rats display a selective impairment in hippocampal-dependent long-term memory, and that dietary CDP-choline supplementation can protect against this deficit.

Cyclooxygenase-2 mediates platelet-activating factor-induced prostaglandin E2 release from rat primary astrocytes

The phospholipid mediator platelet-activating factor (PAF), and its non-hydrolyzable analog methylcarbamyl-PAF (mc-PAF) increase prostaglandin E(2) (PGE(2)) release from astrocyte-enriched cortical cell cultures. Cyclooxygenase (COX) enzymes--of which there are two known isoforms--convert arachidonic acid to prostaglandin (PG) H(2) (PGH(2)), which is further metabolized to various PGs, including PGE(2). COX-1 is generally considered to contribute to cell homeostasis, whereas COX-2 is thought to mediate inflammatory/immune PG formation. In this study we examined the involvement of the COX isoforms in PAF-induced PGE(2) release. Treatment of cells with the non-specific COX inhibitor indomethacin, or the specific COX-2 inhibitor NS-398, prior to mc-PAF stimulation completely blocked the PAF-induced release of PGE(2); treatment with more selective COX-1 inhibitors (i.e. piroxicam and SC-560) failed to significantly do so. These data suggest that COX-2 is responsible for PAF-mediated PGE(2) release in primary astrocytes.

Environmental conditions influence hippocampus-dependent behaviours and brain levels of amyloid precursor protein in rats

Sprague-Dawley rats were reared in enriched (EC; group housing, exposure to stimulating objects, frequent handling) or restricted (RC; individual housing, no exposure to stimulating objects, minimal handling) environments starting on day 23 of life. At six months of age, they underwent behavioural tests to assess 'cognitive' and 'stimulus-response' memory, selective attention, and inflammatory pain processing. Alterations in synapses and cell survival may occur as a result of environment differences; therefore we assessed the brain levels of several proteins implicated in neurite outgrowth, synaptogenesis, and cell survival. Brains were dissected and analysed for amyloid precursor protein (APP) and other synaptic and cytoskeletal proteins using Western blotting. The performance of EC animals in a hidden platform water maze task, and in a test of selective attention (both of which are thought to involve the hippocampus) was superior to that of RC animals. In contrast, performance of RC animals on two stimulus-response tasks, the visible platform water maze test and simple visual discrimination (both of which are thought to be hippocampal independent) was indistinguishable from that of EC animals. Male EC rats displayed a different behavioural response to formalin during the inflammatory phase of nociception--the phase affected by hippocampal processing; a similar trend was observed in females. Female but not male RC rats exhibited elevated plasma corticosterone levels; adrenal weights were unaffected by environmental conditions. Region-specific increases in brain levels of APP, neurofilament-70 (NF-70), and platelet-activating factor receptor (PAF-R) were found in EC rats. These data suggest that enriched animals manifest enhanced functioning of certain hippocampus-mediated behaviours when compared with that of their restricted counterparts; and that brain levels of various synaptic and structural proteins involved in neurite outgrowth, cell survival, and synaptogenesis, are affected by environmental factors.

Platelet-activating factor antagonists decrease the inflammatory nociceptive response in rats

RATIONALE

Platelet-activating factor (PAF) is a membrane-derived phospholipid mediator that has biological effects on a variety of cells and tissues. A variety of stimuli, including those producing inflammation, promote the synthesis and release of PAF from various cell types. Evidence suggests that PAF exerts cellular actions through a plasma membrane receptor as well as via intracellular (microsomal) PAF binding sites.

OBJECTIVE

The present study was designed to: 1) investigate the role of PAF in a model of inflammatory nociception in rats (i.e. the formalin test), and 2) localize PAF's site(s) of action in nociception. To do this, we assessed the effect of administering two PAF antagonists (BN 52021 and BN 50730, which are selective for cell surface and intracellular PAF binding sites, respectively) on formalin-induced nociceptive responses.

METHODS

Forty minutes prior to formalin injection into the rat hindpaw, male Sprague-Dawley rats received systemic injections of BN 52021 (10, 1, or 0.1 mg/kg), BN 50730 (10, 1, or 0.1 mg/kg), or vehicle (45% 2-hydroxypropyl-beta-cyclodextrin in distilled water, HBC) and the effects of the drugs on nociceptive behavioral responses were measured.

RESULTS

Rats receiving systemic BN 52021 or BN 50730 displayed a significant reduction of nociceptive responses in the late, but not early, phase of formalin-induced nociception.

CONCLUSIONS

These findings suggest a role for endogenous PAF in nociceptive transmission, especially for persistent pain such as that which occurs in the late phase of the formalin test. The findings also indicate that both intracellular and cell surface PAF binding sites are involved in nociceptive modulation in rats, and that PAF antagonists might be useful for treating some patients with acute or chronic pain.

Platelet-activating factor increases prostaglandin E(2) release from astrocyte-enriched cortical cell cultures

The phospholipid mediator platelet-activating factor (PAF) increased the release of prostaglandin E(2) (PGE(2)) from astrocyte-enriched cortical cell cultures in a concentration- and time-dependent manner. The nonhydrolyzable PAF analog methylcarbamyl-PAF (mc-PAF), the PAF intermediate lyso-PAF, and arachidonic acid (AA) also produced this effect. In contrast, phosphatidlycholine (PC) and lyso-PC, lipids that are structurally similar to PAF and lyso-PAF, had no effect on PGE(2) production, suggesting that PAF-induced PGE(2) release is not the consequence of nonspecific phospholipid-induced membrane perturbation. Antagonism of intracellular PAF binding sites completely abolished the ability of mc-PAF and lyso-PAF to mobilize PGE(2,) and attenuated the AA effect. Antagonism of the G-protein-coupled PAF receptor in plasma membranes had no significant effect on mc-PAF, lyso-PAF or AA-induced PGE(2) release. Based on the present findings, we hypothesize that intracellular PAF is a physiologic stimulus of PGE(2) production in astrocytes.

Post-training cyclooxygenase-2 (COX-2) inhibition impairs memory consolidation

Evidence indicates that prostanoids, such as prostaglandins, play a regulatory role in several forms of neural plasticity, including long-term potentiation, a cellular model for certain forms of learning and memory. In these experiments, the significance of the COX isoforms cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in post-training memory processes was assessed. Adult male Long-Evans rats underwent an eight-trial (30-sec intertrial interval) training session on a hippocampus-dependent (hidden platform) or dorsal striatal-dependent (visible platform) tasks in a water maze. After the completion of training, rats received an intraperitoneal injection of the nonselective COX inhibitor indomethacin, the COX-1-specific inhibitor piroxicam, the COX-2-specific inhibitor N-[2-cyclohexyloxy-4-nitrophenyl]-methanesulfonamide (NS-398), vehicle (45% 2-hydroxypropyl-beta-cyclodextrin in distilled water), or saline. On a two-trial retention test session 24 h later, latency to mount the escape platform was used as a measure of memory. In the hidden platform task, the retention test escape latencies of rats administered indomethacin (5 and 10 mg/kg) or NS-398 (2 and 5 mg/kg) were significantly higher than those of vehicle-treated rats, indicating an impairment in retention. Injections of indomethacin or NS-398 that were delayed 2 h post-training had no effect on retention. Post-training indomethacin or NS-398 had no influence on retention of the visible platform version of the water maze at any of the doses administered. Furthermore, selective inhibition of COX-1 via post-training piroxicam administration had no effect on retention of either task. These findings indicate that COX-2 is a required biochemical component mediating the consolidation of hippocampal-dependent memory.

Differential interaction of platelet-activating factor and NMDA receptor function in hippocampal and dorsal striatal memory processes

The interaction between platelet activating factor (PAF) and NMDA receptor function in hippocampal and dorsal striatal memory processes was examined. In both a hidden and a visible platform water maze task, peripheral post-training injection of MK-801 (0.05 mg/kg) impaired memory. Post-training intrahippocampal infusions of PAF (1.0 microg/0.5 microl) enhanced memory in the hidden platform task, while intradorsal striatal infusion of PAF (1.0 microg/0.5 microl) enhanced memory in the visible platform task. The memory impairing effects of post-training injection of MK-801 was blocked by concurrent intrahippocampal infusion of PAF. In contrast, post-training injection of MK-801 blocked the memory enhancing effects of concurrent intradorsal striatal infusion of PAF. The results suggest that (1) the memory enhancing effects of intracerebral PAF infusion involve an interaction with NMDA receptor function, and (2) the nature of this interaction may represent a differential mechanism mediating the distinct roles of the hippocampus and dorsal striatum in cognitive memory and stimulus-response habit formation, respectively.

Effects of posttraining intrahippocampal injections of platelet-activating factor and PAF antagonists on memory

The present experiments examined the effects of posttraining intrahippocampal injections of the degradative enzyme-resistant methylcarbamyl analog of the bioactive phospholipid platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) receptor antagonists BN52021 and BN 50730 on memory in male Long-Evans rats trained in a hidden platform version of the Morris water maze. Following an eight-trial training session, rats received a unilateral intrahippocampal injection of mc-PAF (0.5, 1.0, or 2.0 microgram/0.5 microliter), lyso-PAF (1.0 microgram/0.5 microliter), the cell surface PAF receptor antagonist BN 52021 (0.25, 0.5, or 1.0 micrigram/0.5 microliter/, the intracellular PAF receptor antagonist BN 50730 (2.0, 5.0, or 10.0 microgram/0.5 microliter), or vehicle (50% DMSO in 0.9% saline; 0.5 microliter). On a retention test conducted 24 h after training, the escape latencies of rats administered mc-PAF (1.0 or 2.0 microgram) were significantly lower than those of the vehicle-injected controls, demonstrating a memory-enhancing effect of mc-PAF. Injections of lyso-PAF, a structurally similar metabolite of PAF, had no influence on memory, indicating that the memory-enhancing effect of mc-PAF is not caused by membrane perturbation by the phospholipid. The retention test escape latencies of rats administered BN 52021 (0.5 microgram) and BN 50730 (5.0 or 10 microgram) were significantly higher than those of the controls, indicating a memory impairing effect of both PAF antagonists. When mc-PAF, BN 52021, or BN 50730 was administered 2 h posttraining, no effect on retention was observed, indicating a time-dependent effect of the neuroactive substances on memory storage. The findings suggest a role for endogenous PAF in hippocampal-dependent memory processes.

Amygdala modulation of multiple memory systems: hippocampus and caudate-putamen

A series of five experiments examined the differential mnemonic roles of the hippocampus and caudate-putamen and the modulatory influence of the amygdala on hippocampal and caudate-putamen memory processes. Findings indicate that (a) posttraining intrahippocampal injections of amphetamine selectively enhance memory in a hidden platform water maze task, (b) posttraining intracaudate injections of amphetamine selectively enhance memory in a visible platform water maze task, (c) posttraining intra-amygdala injections of amphetamine enhance memory in both water maze tasks, (d) preretention intrahippocampal lidocaine injections block expression of the memory enhancing effects of posttraining intrahippocampal amphetamine injections in the hidden platform task, (e) preretention intracaudate lidocaine injections block expression of the memory enhancing effects of posttraining intracaudate amphetamine injections in the visible platform task, (f) preretention intra-amygdala lidocaine injections do not block the memory enhancing effect of posttraining intra-amygdala amphetamine injections on either task, (g) in the hidden platform task, posttraining intrahippocampal, but not intracaudate, lidocaine injections block the memory enhancing effects of posttraining intra-amygdala amphetamine, (h) in the visible platform task, posttraining intracaudate, but not intrahippocampal, lidocaine injections block the memory enhancing effects of posttraining intra-amygdala amphetamine. The findings indicate a double dissociation between the roles of the hippocampus and caudate-putamen in memory and suggest that the amygdala exerts a modulatory influence on both the hippocampal and caudate-putamen memory systems.

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

The present experiments examined acute posttraining estrogenic influences on memory in ovariectomized rats. In experiment 1 rats received a single 8-trial (30-s ITI) training session with a submerged escape platform located in the same quadrant of a circular water maze on all trials. Following trial 8, rats received a posttraining intraperitoneal injection of either an estradiol-cyclodextrin inclusion complex (0.1, 0.2, or 0.4 mg/kg) or saline. On a retention test session 24 h later, the escape latencies of rats given injections of estradiol (0.2 mg/kg) were significantly lower than those of saline-treated rats, indicating an enhancement of memory. Injections of estradiol delayed 2 h posttraining did not affect retention, demonstrating a time-dependent effect of estradiol on memory storage processes. In experiment 2a, posttraining injections of the cholinergic muscarinic receptor antagonist scopolamine (0.4 mg/kg) impaired memory in ovariectomized rats. In experiment 2b, the memory-enhancing effect of estradiol (0.2 mg/kg) was blocked by concurrent posttraining administration of a subeffective dose (0.1 mg/kg) of scopolamine, suggesting an interaction between estradiol and muscarinic cholinergic systems in memory modulation. In experiment 3a, posttraining injections of the cholinergic muscarinic receptor agonist oxotremorine (0.2 mg/kg) enhanced memory in ovariectomized rats. In experiment 3b, concurrent posttraining injection a subeffective dose of estradiol (0.1 mg/kg) and a subeffective dose of oxotremorine (0.1 mg/kg) enhanced memory, indicating a synergistic effect of estradiol and muscarinic receptor activation on memory.

Double dissociation of hippocampal and dorsal-striatal memory systems by posttraining intracerebral injections of 2-amino-5-phosphonopentanoic acid

Rats received an 8-trial training session on a spatial or cued task in a water maze, followed by a posttraining intracerebral injection of AP5 or saline. On a retention test 24 hr later, latency to mount the escape platform was used as a measure of memory. Intrahippocampal (10 micrograms), but not intra-dorsal striatal (2, 5, or 10 micrograms), injection of AP5 impaired memory in the spatial task. In contrast, intra-dorsal striatal (2 micrograms), but not intrahippocampal (2, 5, or 10 micrograms) injection of AP5 impaired memory in the cued task. Intracerebral injections of AP5 delayed 2 hr posttraining were ineffective. The findings indicate a double dissociation of the roles of the hippocampus and dorsal striatum in memory, a role for N-methyl-D-aspartate receptor function in posttraining memory processes, and a glutamatergic modulation of both hippocampal and dorsal striatal memory processes, suggesting that different forms of memory may share a similar neurochemical basis.

Posttraining injections of MK-801 produce a time-dependent impairment of memory in two water maze tasks

The role of glutamatergic N-methyl-D-aspartate (NMDA) receptors in memory storage processes was examined using systemic posttraining injections of MK-801. Male Long-Evans rats received an eight-trial (30-s ITI) training session on a spatial or cued water maze task. In the spatial task, a submerged escape platform was located in the same quadrant of the maze on all trials. In the cued task, a visible escape platform was located in a different quadrant of the maze on each trial. Following Trial 8 in both tasks, the rats received a posttraining intraperitoneal injection of the NMDA receptor antagonist MK-801 (0.025, 0.05, 0.1, or 0.2 mg/kg) or saline. On a retention test session 24 h later, latency to mount the escape platform was used as a measure of memory. In both tasks, the retention test escape latencies of animals given MK-801 (0.05 and 0.1 mg/kg) were significantly higher than those of saline-injected controls, indicating a drug-induced impairment of memory. Injections of MK-801 (0.05 mg/kg) did not affect retention when administered 2 h posttraining in either task, indicating that the effects of MK-801 on retention are not due to an influence on non-mnemonic factors. Control experiments indicated that the memory impairing effects of MK-801 were due to an influence on memory for the type of discrimination training given (i.e., spatial or cued) and not due to an influence on a mnemonic strategy common to both tasks. The findings indicate a time-dependent role for NMDA receptor function in memory storage processes.

Double dissociation of hippocampal and dorsal-striatal memory systems by posttraining intracerebral injections of 2-amino-5-phosphonopentanoic acid

Rats received an 8-trial training session on a spatial or cued task in a water maze, followed by a posttraining intracerebral injection of AP5 or saline. On a retention test 24 hr later, latency to mount the escape platform was used as a measure of memory. Intrahippocampal (10 micrograms), but not intra-dorsal striatal (2, 5, or 10 micrograms), injection of AP5 impaired memory in the spatial task. In contrast, intra-dorsal striatal (2 micrograms), but not intrahippocampal (2, 5, or 10 micrograms) injection of AP5 impaired memory in the cued task. Intracerebral injections of AP5 delayed 2 hr posttraining were ineffective. The findings indicate a double dissociation of the roles of the hippocampus and dorsal striatum in memory, a role for N-methyl-D-aspartate receptor function in posttraining memory processes, and a glutamatergic modulation of both hippocampal and dorsal striatal memory processes, suggesting that different forms of memory may share a similar neurochemical basis.

Effects of intrastriatal injections of platelet-activating factor and the PAF antagonist BN 52021 on memory

The present experiments examined the effects of posttraining intra-dorsal striatal (i.e., caudate-putamen) injections of the phospholipid methylcarbamyl platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) antagonist BN 52021 on memory using a striatal-dependent cued water maze task. Male Long-Evans rats received an eight-trial training session in which a visibly cued escape platform was located in a different quadrant of the maze on each trial, followed by an intrastriatal injection of mc-PAF (0.5, 1.0, or 2.0 micrograms/0.5 microliter), BN 52021 (0.25, 0.5, or 1.0 microgram/0.5 microliter), or vehicle (DMSO; 0.5 microliter). On a retention test 24 h later, the escape latencies of rats given mc-PAF (1.0, 2.0 micrograms) wee significantly lower than those of vehicle-injected controls, indicating a memory enhancing effect of mc-PAF. The retention test escape latencies of rats given BN 52021 (0.5, 1.0 microgram) were significantly higher than those of vehicle-injected controls, indicating a memory impairing effect of BN 52021. Injections of mc-PAF or BN 52021 did not affect retention when administered 2-h posttraining, indicating a time-dependent effect of the drugs on memory storage. The findings indicate a role for endogenous PAF function in striatal-dependent memory processes.