Fungal hallucinogens psilocin, ibotenic acid, and muscimol: analytical methods and biologic activities.

Psychoactive drugs of fungal origin, psilocin, ibotenic acid, and muscimol among them have been proposed for recreational use and popularized since the 1960s, XX century. Despite their well-documented neurotoxicity, they reached reputation of being safe and nonaddictive. Scientific efforts to find any medical application for these hallucinogens in psychiatry, psychotherapy, and even for religious rituals support are highly controversial. Even if they show any healing potential, their usage in psychotherapy is in some cases inadequate and may additionally harm seriously suffering patients. Hallucinogens are thought to reduce cognitive functions. However, in case of indolealkylamines, such as psilocin, some recent findings suggest their ability to improve perception and mental skills, what would motivate the consumption of "magic mushrooms." The present article offers an opportunity to find out what are the main symptoms of intoxication with mushrooms containing psilocybin/psilocin, muscimol, and ibotenic acid. The progress in analytical methods for detection of them in fungal material, food, and body fluids is reviewed. Findings on the mechanisms of their biologic activity are summarized. Additionally, therapeutic potential of these fungal psychoactive compounds and health risk associated with their abuse are discussed.

The glutamatergic component of the mesocortical pathway emanating from different subregions of the ventral midbrain.

The mesocortical pathway projecting from the ventral tegmental area (VTA) to the prefrontal cortex (PFC) plays a critical role in a number of cognitive and emotional processes. While this pathway has been traditionally viewed as dopaminergic, recent data indicate that a considerable proportion of rostromedial VTA neurons possess markers for glutamate transmission. However, the relative density of the glutamatergic projection to the PFC from these rostromedial regions is unknown. In the present study, anterograde tracer injections into 4 ventral midbrain subregions were coupled with immunohistochemical analysis of labeled axons in PFC for markers of dopamine (DA; tyrosine hydroxylase [TH]) and glutamate (vesicular glutamate transporter 2; VGLUT2). We found that while tracer injections into the interfascicular nucleus produced labeled fibers in the PFC that were mainly TH positive, tracer injections into the rostral linear nucleus, rostral VTA, and parabrachial pigmented nucleus produced labeled fibers in PFC that contained mainly VGLUT2-positive rather than TH-positive varicosities. When viewed in the light of the previously documented strong γ-aminobutyric acidergic component, it would seem that the rostromedial mesocortical projection is actually an amino acid pathway that in addition has a DA component.

Dorsal hippocampal lesions boost performance in the rat sequential reaction time task.

It is commonly accepted that the hippocampus plays a major role in declarative memory across species and that it is of particular relevance for spatial memory in rodents. However, the interplay between hippocampal function and nondeclarative memory systems, such as procedural stimulus-response (S-R) or sequential learning, is less clear: depending on task requirements, an interaction, dissociation or interference between hippocampal function and other memory systems may occur. This study was conducted to investigate the influence of dorsal ibotenic hippocampal lesions on learning and performance of sequential behavior in a rat version of the serial reaction time task (SRTT). Magnetic resonance imaging (MRI) analyses of the lesions revealed a bilateral volume reduction of ≈ 46% (histological analyses: ≈ 59%) of the total hippocampus. They were largely confined to its dorsal part and led to an expected spatial memory deficits in an object place recognition test as compared to healthy controls, even though sham lesions had the same effect. Our earlier studies on sequential learning had revealed substantial impairments in case of dorsal striatal dopaminergic lesions. In the present study, however, hippocampal lesioned animals unexpectedly showed superior performance throughout SRTT testing and training as compared to controls, which resulted in a higher degree of subsequent automated sequential behavior. Thus, our data reveal the infrequent case where hippocampal lesions lead to long-term improvements in test performance of a type of rather complex procedural behavior. One possible explanation for this effect is that hippocampal activity in rodents can interfere with other memory systems during the acquisition of procedural tasks with very low spatial requirements, as used here. Alternative explanations for the observed superior SRTT performance in lesioned animals, such as hyperactivity or increased exploratory drive are also topic of the discussion.

Follow-up of cortical activity and structure after lesion with laser speckle imaging and magnetic resonance imaging in nonhuman primates.

The nonhuman primate model is suitable to study mechanisms of functional recovery following lesion of the cerebral cortex (motor cortex), on which therapeutic strategies can be tested. To interpret behavioral data (time course and extent of functional recovery), it is crucial to monitor the properties of the experimental cortical lesion, induced by infusion of the excitotoxin ibotenic acid. In two adult macaque monkeys, ibotenic acid infusions produced a restricted, permanent lesion of the motor cortex. In one monkey, the lesion was monitored over 3.5 weeks, combining laser speckle imaging (LSI) as metabolic readout (cerebral blood flow) and anatomical assessment with magnetic resonance imaging (T2-weighted MRI). The cerebral blood flow, measured online during subsequent injections of the ibotenic acid in the motor cortex, exhibited a dramatic increase, still present after one week, in parallel to a MRI hypersignal. After 3.5 weeks, the cerebral blood flow was strongly reduced (below reference level) and the hypersignal disappeared from the MRI scan, although the lesion was permanent as histologically assessed post-mortem. The MRI data were similar in the second monkey. Our experiments suggest that LSI and MRI, although they reflect different features, vary in parallel during a few weeks following an excitotoxic cortical lesion.

Implanted neurosphere-derived precursors promote recovery after neonatal excitotoxic brain injury.

Brain damage through excitotoxic mechanisms is a major cause of cerebral palsy in infants. This phenomenon usually occurs during the fetal period in human, and often leads to lifelong neurological morbidity with cognitive and sensorimotor impairment. However, there is currently no effective therapy. Significant recovery of brain function through neural stem cell implantation has been shown in several animal models of brain damage, but remains to be investigated in detail in neonates. In the present study, we evaluated the effect of cell therapy in a well-established neonatal mouse model of cerebral palsy induced by excitotoxicity (ibotenate treatment on postnatal day 5). Neurosphere-derived precursors or control cells (fibroblasts) were implanted into injured and control brains contralateral to the site of injury, and the fate of implanted cells was monitored by immunohistochemistry. Behavioral tests were performed in animals that received early (4 h after injury) or late (72 h after injury) cell implants. We show that neurosphere-derived precursors implanted into the injured brains of 5-day-old pups migrated to the lesion site, remained undifferentiated at day 10, and differentiated into oligodendrocyte and neurons at day 42. Although grafted cells finally die there few weeks later, this procedure triggered a reduction in lesion size and an improvement in memory performance compared with untreated animals, both 2 and 5 weeks after treatment. Although further studies are warranted, cell therapy could be a future therapeutic strategy for neonates with acute excitotoxic brain injury.

Memory improvement in ibotenic acid induced model rats by extracts of Scutellaria baicalensis.

ETHNOPHARMACOLOGICAL RELEVANCE: Scutellaria baicalensis Georgi (Labiatae) extracts have been used as traditional Korean medicine, to treat cerebral ischemia in addition to bacterial infection and inflammatory diseases. AIM OF THE STUDY: The improvement effect on learning and memory by the administration of Scutellaria baicalensis extracts was evaluated and the underlying mechanisms were investigated. MATERIALS AND METHODS: Memory behavior was tested by the passive avoidance test and Y-maze test. We also investigated the cells expressing neuronal markers related to memory processes by immunofluorescence staining analysis in memory deficient animal model (Ibo model) rats and in hippocampal progenitor cells. RESULTS: We found neuronal cells immunoreactive to choline acetyltransferase (ChAT), a marker for cholinergic neurons were increased in the hippocampus, while cells producing GABA and glutamate were not after 30 mg/kg Scutellaria baicalensis administration. Futhermore, Scutellaria baicalensis extracts enhanced the survival of a hippocampal progenitor cell line, HiB5 and its differentiation to ChAT immunoreactive cells. The increased expression of memory related neurotransmitter, NMDA receptor and a reduction of activated microglia in the hippocampus were also observed in the Ibo model when administrated Scutellaria baicalensis extracts. CONCLUSIONS: These results imply that Scutellaria baicalensis has significant neuroprotective effects in the Ibo model.

Dorsal hippocampus, CA3, and CA1 lesions disrupt temporal sequence completion.

An experiment was designed to evaluate effects of dorsal hippocampus, dorsal CA3a,b, dorsal CA1, and control lesions on performance of a temporal sequence task. Rats were trained on a sequential learning task involving six spatial locations on a radial 8-arm maze. After initial training followed by surgery, it was found that all lesioned animals were able to remember the sequence. To test temporal sequence completion, rats were started at different positions in the sequence and expected to complete the remainder of the sequence. The results indicate that control rats had no difficulty completing the sequence, regardless of starting point. In contrast, rats with dorsal hippocampus and dorsal CA3a,b lesions made errors by always returning to the first position in the sequence, regardless of which start position was used, whereas rats with dorsal CA1 lesions made random errors in the process of completing the sequence and did not appear to remember the serial order of the spatial sequence. This suggests that the dorsal hippocampus, and specifically the dorsal CA3 in conjunction with CA1, may be involved in temporal pattern completion processes.

Involvement of subthalamic nucleus in the stimulatory effect of Delta(9)-tetrahydrocannabinol on dopaminergic neurons.

The cannabinoid CB1 receptor which is densely located in the basal ganglia is known to participate in the regulation of movement. The present study sought to determine the mechanisms underlying the effect of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) on neurons in the substantia nigra pars compacta (SNpc) using single-unit extracellular recordings in anesthetized rats. Administration of Delta(9)-THC (0.25-2 mg/kg, i.v.) increased the firing rate of SNpc neurons (maximal effect: 33.54+/-6.90%, n=8) without modifying other firing parameters (coefficient of variation and burst firing). This effect was completely blocked by the cannabinoid receptor antagonist rimonabant (0.5 mg/kg, i.v.). In addition, the blockade of excitatory amino acids receptors by kynurenic acid (0.5 microM, i.c.v.) or a chemical lesion of the subthalamic nucleus (STN) with ibotenic acid abolished Delta(9)-THC effect. These results indicate that CB1 receptor activation modulates SNpc neuronal activity by an indirect mechanism involving excitatory amino acids, probably released from STN axon terminals in the SNpc.

Effects of central and basolateral amygdala lesions on conditioned taste aversion and latent inhibition.

The present study examined the effects of neurotoxic lesions of the central nucleus (CNA) and basolateral complex (BLA) of the amygdala on conditioned taste aversion (CTA) in a latent inhibition design. In Experiment 1, lesions of the CNA were found to have no affect on CTA acquisition regardless of whether the taste conditioned stimulus (CS) was novel or familiar. Lesions of the BLA, although having no influence on performance when the CS was familiar, retarded CTA acquisition when the CS was novel in Experiment 2. The pattern of results suggests that the CTA deficit in rats with BLA lesions may be a secondary consequence of a disruption of perceived stimulus novelty.

Role of substantia innominata in cerebral blood flow autoregulation.

Ascending projections from the substantia innominata (SI) may have an important role in the regulation of cerebral blood flow (CBF). However, several reports have suggested that unilateral lesion of the SI does not affect CBF autoregulation. On the other hand, it is also reported that several cortical and subcortical functions may be regulated not only by ipsilateral SI, but also by contralateral SI. Thus, the objective of this study is to test the hypothesis that bilateral lesions of the SI affect CBF autoregulation. Experiments were performed on anesthetized male Sprague-Dawley rats. Ibotenic acid or physiological saline was microinjected into bilateral SI. Rats were classified into four groups as follows: bilateral SI lesion rats (ibotenic acid was injected bilaterally), left or right SI lesion rats (ibotenic acid was injected into the unilateral SI and saline into the contralateral SI), and control rats (saline was injected bilaterally). Ten days after injection, CBF in the left frontal cortex was measured by laser-Doppler flowmetry during stepwise controlled hemorrhagic hypotension. In bilateral SI lesion rats, CBF was started to decrease significantly at 80 mm Hg (p<0.01). In the other three groups, CBF was well maintained until 50 mm Hg. Changes in CBF through stepwise hypotension in bilateral SI lesion rats were significantly different from the other groups (p<0.01). These results suggest that bilateral SI regulates cortical vasodilator mechanisms during hemorrhagic hypotension. Under unilateral SI lesion, some compensatory effects from the contralateral SI may maintain CBF autoregulation.

Effects of partial hippocampal lesions by ibotenic acid on repeated acquisition of spatial discrimination in pigeons.

Pigeons were trained on a spatial discrimination task using a repeated acquisition procedure. In this procedure, the pigeons were trained to discriminate between the positions of three keys. One of them was designated the correct key. When the subjects reached the criterion, the discrimination task was changed, with one of two previously incorrect keys now being made the correct key. This procedure was repeated at least 15 times. Then, lesions to the whole hippocampus, the medial hippocampus or to the lateral hippocampus were made by injections of ibotenic acid (Experiment 1). Only the subjects with damage to the whole hippocampus showed deficits in learning after the lesions. The deficits were similar to those caused by aspiration lesions /37/. Knife cuts separating the medial and lateral hippocampi were made in Experiment 2. The subjects did not show deficits in the spatial discrimination task after the sections. Although studies of the connectivity in the avian hippocampus suggested functional differences between the medial and lateral hippocampi, the present results show that pigeons can learn spatial discrimination with the medial and lateral parts of hippocampus separated.

Neonatal lesions of the ventral hippocampus in rats lead to prefrontal cognitive deficits at two maturational stages.

This experiment assessed the effect of neonatal ventral hippocampus lesions in rats, a heuristic approach to model schizophrenia, on continuous delayed alternation and conditional discrimination learning performance before and after complete cerebral maturation. Delays (0, 5, 15, and 30 s) were introduced in the tasks to help dissociate between a hippocampal and a prefrontal cortex dysfunction. At postnatal day (PND) 6 or 7, rats received bilateral microinjections of ibotenic acid or phosphate-buffered saline in the ventral hippocampus. From PND 26 to PND 35, rats were tested on the alternation task in a T-maze; from PND 47 to PND 85, the same rats were tested in the discrimination task where a stimulus and a response location had to be paired. Deficits in ventral hippocampus-lesioned rats were observed in both tasks whether a delay was introduced before a response or not. Impaired performance regardless of delay length, combined with high rates of perseverative errors, suggested a post-lesional prefrontal cortex dysfunction which persisted from the juvenile stage into adulthood. Premature cognitive impairments could not be predicted on the basis of the neurodevelopmental animal model of schizophrenia. Nevertheless, they appear consistent with accounts of premorbidly compromised memory, both immediate and delayed, in subgroups of schizophrenia patients.

The role of CA3 and CA1 in the acquisition of an object-trace-place paired-associate task.

The hippocampus mediates associative learning involving spatial and temporal information. Specifically, paired associations in which a trace interval separates the elements appear to be associated within CA1. In contrast, CA3 appears to be involved in associations containing spatial elements. This suggests that CA3, but not CA1, is involved as long as the spatial association does not contain temporal elements; conversely, CA1 is involved when a temporal element is included, regardless of whether there are spatial elements present. In the present study, rats were run on an object-trace-place paired-associate learning paradigm. Rats with CA3 as well as rats with CA1 lesions showed deficits in the acquisition of this task. These results suggest that CA1 is involved in making arbitrary associations involving a temporal (trace) element, whereas CA3 is involved in making associations that involve spatial elements; furthermore, CA1 and CA3 interact in the presence of both spatial and temporal information.

Radial and tangential neuronal migration disorder in ibotenate-induced cortical lesions in hamsters: immunohistochemical study of reelin, vimentin, and calretinin.

To investigate the mechanisms of radial and tangential neuronal migration disorders, immunohistochemical expressions of reelin, vimentin, and calretinin were examined in brain lesions induced by ibotenate (an agonist of the N-methyl-D-aspartate [NMDA] complex receptor) in hamsters. Thirty-four newborn hamsters were subjected to intracerebral injections of ibotenate, and 12 animals served as the control. These hamsters were examined at 1, 2, 3, 5, and 7 days after injections. The cortical lesions observed after ibotenate injections had a strong resemblance to the following neuronal migration disorders: (1) microgyria, (2) focal subcortical heterotopia, and (3) leptomeningeal glioneuronal heterotopia. In microgyria, the radial glial fibers were sparsely distributed, but in leptomeningeal glioneuronal heterotopia, vimentin-positive fibers extended into this abnormal neural tissue. Calretinin-immunoreactive neurons and fibers were present along the lesion forming the microgyria and abnormal neuronal arrangement. Focal subcortical heterotopia also included a small number of calretinin-expressing neurons originating from the subplate neuronal population. These results imply that the neuronal migration disorders produced by ibotenate show not only the migrational arrest of neurons but also interference from the termination of the migration process. We also suggest that the heterotopic neurons constituting the focal subcortical heterotopia originate in the lateral or medial ganglionic eminence of the ventral telencephalon, probably caused by the abnormal tangential neuronal migration.

Glucocorticoid treatment in an ischaemic-like excitotoxic model of periventricular leucomalacia in mice.

OBJECTIVE: To determine the effects of fluorinated glucocorticoids on the occurrence and extent of ischaemic-like excitotoxic grey and white matter cerebral injuries in an animal model. DESIGN: A study of the influence of single or repeated doses of glucocorticoids when creating excitotoxic lesions in mice pups, mimicking some aspects of periventricular leucomalacia and cortical-subcortical stroke as observed in human neonates. SAMPLE: Four hundred and sixty-seven mouse pups out of more than 30 litters. METHODS: An excitotoxic lesion was created by intracerebral injection of ibotenate, a glutamatergic agonist, in day five postnatal mice pups. A single dose of betamethasone or dexamethasone was administered, in a dose of 0.006-6 and 0.001-1 mg/kg, respectively, 24 hours before or 15 minutes after each ibotenate injection. Repeated doses of dexamethasone (0.01 mg/kg per day) or betamethasone (0.006 mg/kg) were given for five days before or after ibotenate injections. The measurement of white matter and grey matter lesions and the occurrence of cysts were assessed under light microscope on cresyl violet-stained brain sections. MAIN OUTCOME MEASURES: Size of white matter cystic lesions. RESULTS: A single injection of betamethasone or dexamethasone had a significant neuroprotective effect when administered after the excitotoxin. Betamethasone injected once prior to ibotenate also had a protective effect. Repeated administration of each steroid before or after excitotoxin injection provided more protection than a single injection. CONCLUSION: Fluorinated glucocorticoids reduced neonatal brain lesions observed in a mouse model treated by excitotoxin injection.

Effects of ibotenic acid lesions of the nucleus accumbens on paced mating behavior in the female rat.

The present study investigated the role of the nucleus accumbens (NAcc) in paced mating behavior in female rats. A sexually receptive female rat will approach and withdraw from a sexually active male, thereby controlling the timing of the receipt of sexual stimulation (e.g., mounts, intromissions, ejaculations). In this study, ibotenic acid lesions in the NAcc core increased the likelihood that a female rat would withdraw from a male rat after a mount but did not affect contact return latency or sexual receptivity. Ibotenic acid lesions in the NAcc shell did not affect paced mating behavior or sexual receptivity. The results suggest that the NAcc core plays a role in suppressing withdrawal behavior in response to less intense mating stimulation.

Ibotenic acid lesions of the medial septum retard delay eyeblink conditioning in rabbits (Oryctolagus cuniculus).

S. Berry and R. Thompson (1979) reported that electrolytic lesions of the medial septum significantly retard eyeblink conditioning. However, these electrolytic lesions were nonselective and may have also damaged the subcortical inputs to the hippocampus via the fimbria-fornix. In the present study, the medial septum was selectively lesioned with ibotenic acid in rabbits (Oryctolagus cuniculus), whose performance in a delay eyeblink conditioning paradigm was compared with that of intact controls. sham-operated controls, and intact controls given a systemic injection of scopolamine. Rabbits with selective medial septal lesions and rabbits receiving systemic scopolamine were significantly slower to condition than were intact and sham-lesioned rabbits. This finding demonstrates that the selective removal of the medial septum retards delay eyeblink conditioning in a manner similar to the disruption seen after systemic administration of scopolamine.

Deficits in reward sensitivity in a neurodevelopmental rat model of schizophrenia.

RATIONALE: Neonatal ventral hippocampal lesions in rats have been shown to result in behavioral abnormalities at adulthood thought to simulate some aspects of positive and cognitive deficits classically observed in schizophrenic patients. OBJECTIVES: We investigated whether such lesions can also induce deficits in reward sensitivity that are related to the negative symptoms of psychotic disorders. METHODS: To investigate the effects of neonatal and adult lesions of the ventral hippocampus on reward-related behaviors we used the conditioned place preference (CPP) test and the saccharin consumption model. RESULTS: In contrast to adult-lesioned animals, neonatally lesioned rats exhibited a deficit in amphetamine-induced CPP and a significant reduction in saccharin preference. These deficits are unlikely due to lesion-induced motor impairments as both neonatal- and adult-lesioned rats exhibited a similar hyperlocomotor response to amphetamine. CONCLUSIONS: Taken together, these results show that neonatal ventral hippocampal lesions induce a reduction in reward-seeking behaviors in adulthood that mimic some aspects of the negative symptoms (anhedonia) in psychotic patients.

Excitotoxic lesions of the pre- and parasubiculum disrupt object recognition and spatial memory processes.

Rats with bilateral ibotenic acid lesions centered on the pre- and parasubiculum and control rats were tested in a series of spatial memory and object recognition memory tasks. Lesioned rats were severely impaired relative to controls in both the reference and working memory versions of the water maze task and displayed a delay-dependent deficit in a delayed nonmatch to place procedure conducted in the T-maze. Lesioned rats also displayed reduced exploration in a novel environment, and performance was altered in an object recognition procedure as compared with the control group. These findings indicate that the pre- and parasubiculum plays an important role in the processing of both object recognition and spatial memory.

Glycine reduces novelty- and methamphetamine-induced locomotor activity in neonatal ventral hippocampal damaged rats.

The use of neonatal ventral hippocampal nVH lesioned rats is well established in animal models of schizophrenia. Moreover, the dysfunction of N-methyl-D-aspartate (NMDA) neurotransmission may play a crucial role in the pathophysiology of schizophrenia. To examine the effect of glycine (GLY) in this animal model, we compared the effects of GLY (0.8 and 1.6 g/kg, IP) on locomotor activity induced by a novel environment (NOVEL) and methamphetamine (MAP, 1.5 mg/kg, IP) in lesioned and sham-operated rats. Compared with sham rats, GLY significantly reduced NOVEL- and MAP-induced locomotor activity in lesioned rats (p <.001 and p <.05, respectively). It is suggested that GLY attenuated nVH-induced hyperactivity, and that this effect was evident both in the presence and absence of MAP. The nVH lesions may result in a form of hyperactivity that differs from normal locomotion in the degree to which it is highly sensitive to regulation by GLY.