Valeria Capurro

PHARMACOLOGIC RESCUE OF IMPAIRED COGNITIVE FLEXIBILITY, SOCIAL DEFICITS, INCREASED AGGRESSION, AND SEIZURE SUSCEPTIBILITY IN OXYTOCIN RECEPTOR NULL MICE: A NEUROBEHAVIORAL MODEL OF AUTISM

BACKGROUND Oxytocin (OT) has been suggested as a treatment to improve social behavior in autistic patients. Accordingly, the OT (Oxt(-/-)) and the OT receptor null mice (Oxtr(-/-)) display autistic-like deficits in social behavior, increased aggression, and reduced ultrasonic vocalization. METHODS Oxtr(-/-) mice were characterized for general health, sociability, social novelty, cognitive flexibility, aggression, and seizure susceptibility. Because vasopressin (AVP) and OT cooperate in controlling social behavior, learning, and aggression, they were tested for possible rescue of the impaired behaviors. Primary hyppocampal cultures from Oxtr(+/+) and Oxtr(-/-) mouse embryos were established to investigate the balance between gamma-aminobutyric acid (GABA) and glutamate synapses and the expression levels of OT and AVP (V1a) receptors were determined by autoradiography. RESULTS Oxtr(-/-) mice display two additional, highly relevant, phenotypic characteristics: 1) a resistance to change in a learned pattern of behavior, comparable to restricted interests and repetitive behavior in autism, and 2) an increased susceptibility to seizures, a frequent and clinically relevant symptom of autism. We also show that intracerebral administration of both OT and AVP lowers aggression and fully reverts social and learning defects by acting on V1a receptors and that seizure susceptibility is antagonized by peripherally administered OT. Finally, we detect a decreased ratio of GABA-ergic versus total presynapses in hippocampal neurons of Oxtr(-/-) mice. CONCLUSIONS Autistic-like symptoms are rescued on administration of AVP and OT to young Oxtr(-/-) adult animals. The Oxtr(-/-) mouse is thus instrumental to investigate the neurochemical and synaptic abnormalities underlying autistic-like disturbances and to test new strategies of pharmacologic intervention.

Chronic |[Delta]|9-Tetrahydrocannabinol During Adolescence Provokes Sex-Dependent Changes in the Emotional Profile in Adult Rats: Behavioral and Biochemical Correlates

Few and often contradictory reports exist on the long-term neurobiological consequences of cannabinoid consumption in adolescents. The endocannabinoid system plays an important role during the different stages of brain development as cannabinoids influence the release and action of different neurotransmitters and promote neurogenesis. This study tested whether long-lasting interference by cannabinoids with the developing endogenous cannabinoid system during adolescence caused persistent behavioral alterations in adult rats. Adolescent female and male rats were treated with increasing doses of Δ9-tetrahydrocannabinol (THC) for 11 days (postnatal day (PND) 35–45) and left undisturbed until adulthood (PND 75) when behavioral and biochemical assays were carried out. CB1 receptor level and CB1/G-protein coupling were significantly reduced by THC exposure in the amygdala (Amyg), ventral tegmental area (VTA) and nucleus accumbens (NAc) of female rats, whereas male rats had significant alterations only in the amygdala and hippocampal formation. Neither female nor male rats showed any changes in anxiety responses (elevated plus maze and open-field tests) but female rats presented significant ‘behavioral despair’ (forced swim test) paralleled by anhedonia (sucrose preference). In contrast, male rats showed no behavioral despair but did present anhedonia. This different behavioral picture was supported by biochemical parameters of depression, namely CREB alteration. Only female rats had low CREB activity in the hippocampal formation and prefrontal cortex and high activity in the NAc paralleled by increases in dynorphin expression. These results suggest that heavy cannabis consumption in adolescence may induce subtle alterations in the emotional circuit in female rats, ending in depressive-like behavior, whereas male rats show altered sensitivity to rewarding stimuli.

Changes in hippocampal morphology and neuroplasticity induced by adolescent THC treatment are associated with cognitive impairment in adulthood

Marijuana and hashish are the illicit drugs most frequently used by human adolescents. Given the continued neurodevelopment throughout adolescence, adolescents may be more vulnerable than adults to certain neural consequences of heavy marijuana use. This study aimed to assess whether an experimental model of adolescent chronic exposure to Δ9‐tetrahydrocannabinol (THC), may induce lasting effects on learning and memory. Adolescent rats have been treated with THC or its vehicle from 35 to 45 postnatal days (PND) and left undisturbed until their adulthood (75 PND) when aversive and spatial memory was assessed using the passive avoidance and radial maze tasks. No alteration was found in aversive memory, but in the radial maze THC pretreated animals exhibited a worse performance than vehicles, suggesting a deficit in spatial working memory. To correlate memory impairment to altered neuroplasticity, level of marker proteins was investigated in the hippocampus, the most relevant area mediating spatial memory. A significant decrease in the astroglial marker glial fibrillar acid protein was found as well as in pre‐ and postsynaptic protein expression (VAMP2, PSD95) and NMDA receptor levels in pretreated rats. To parallel these changes to alteration in dendritic morphology, Golgi‐Cox staining was performed in the hippocampal dentate gyrus. Pretreated rats had a significantly lower total dendritic length and number than vehicles, as well as reduced spine density. Our data suggest that THC pretreated rats may establish less synaptic contacts and/or less efficient synaptic connections throughout the hippocampus and this could represent the molecular underpinning of the cognitive deficit induced by adolescent THC treatment.

Potential anxiolytic- and antidepressant-like effects of salvinorin A, the main active ingredient of Salvia divinorum, in rodents

Background and purpose:  Drugs targeting brain κ‐opioid receptors produce profound alterations in mood. In the present study we investigated the possible anxiolytic‐ and antidepressant‐like effects of the κ‐opioid receptor agonist salvinorin A, the main active ingredient of Salvia divinorum, in rats and mice.

The Depressive Phenotype Induced in Adult Female Rats by Adolescent Exposure to THC is Associated with Cognitive Impairment and Altered Neuroplasticity in the Prefrontal Cortex

We recently demonstrated that Δ9-tetrahydrocannabinol (THC) chronic administration in female adolescent rats induces alterations in the emotional circuit ending in depressive-like behavior in adulthood. Since cognitive dysfunction is a major component of depression, we assessed in these animals at adulthood different forms of memory. Adolescent female rats were treated with THC or its vehicle from 35 to 45 post-natal days (PND) and left undisturbed until their adulthood (75 PND) when aversive and spatial memory was assessed using the passive avoidance and radial maze tasks. No alteration was found in aversive memory, but in the radial maze THC pre-treated animals exhibited a worse performance than vehicles, suggesting a deficit in spatial working memory. To correlate memory impairment to altered neuroplasticity, level of marker proteins was investigated in the hippocampus and prefrontal cortex, the most relevant areas for learning and memory. A significant decrease in synaptophysin and PSD95 proteins was found in the prefrontal cortex of THC pre-treated rats, with no alterations in the hippocampus. Finally, proteomic analysis of the synapses in the prefrontal cortex revealed the presence of less active synapses characterized by reduced ability in maintaining normal synaptic efficiency. This picture demonstrates the presence of cognitive impairment in THC-induced depressive phenotype.

Involvement of κ-Opioid and Endocannabinoid System on Salvinorin A-Induced Reward

Background The recreational drug, Salvinorin A, derived from the plant of Salvia divinorum, is a potent and selective κ-opioid receptor agonist. The abuse of selective k-agonists is a novel phenomenon, the mechanism of which is not fully understood. Methods We investigated salvinorin A given SC on the conditioned place preference (.05–160 μg/kg) and intracerebroventricular (ICV) self-administration (.01–1 μg/infusion) paradigms, in Wistar rats. Results The present results demonstrate the rewarding effects of Salvinorin A in a range of doses between .1 and 40 μg/kg SC for conditioned place preference test and .1–.5 μg/infusion for ICV self-administration. Highest doses (160 μg/kg for conditioned place preference test and 1 μg/infusion for ICV self-administration) were aversive. The rewarding effect was antagonized by intraperitoneal (IP) pretreatment with the cannabinoid CB 1 receptor antagonist, rimonabant [N-piperidino-5-(4-chlorophenyl)1-(2,4-dichloro phenyl)-4 methyl pyrazole 3-carboxamide] (1 mg/kg), and the κ-opioid receptor antagonist, nor-binaltorphimine (nor-BNI) (10 mg/kg). In the shell of nucleus accumbens, dopamine extracellular levels were increased after administration of salvinorin A (40 μg/kg SC), reaching a maximum value of about 150%. Conclusions These data provide the demonstration of the rewarding effects of Salvinorin A through an interaction between κ-opioid and (endo)cannabinoid system in rats.

Δ9‐Tetrahydrocannabinol (THC) and AM 404 protect against cerebral ischaemia in gerbils through a mechanism involving cannabinoid and opioid receptors

It has been suggested that the endocannabinoid system elicits neuroprotection against excitotoxic brain damage. In the present study the therapeutic potential of AM 404 on ischaemia‐induced neuronal injury was investigated in vivo and compared with that of the classical cannabinoid receptor type 1 (CB1) agonist, Δ9‐tetraydrocannabinol (THC), using a model of transient global cerebral ischaemia in the gerbil.

Learning and Memory Impairment Induced by Salvinorin A, the Principal Ingredient of Salvia divinorum, in Wistar Rats

The effects of salvinorin A (Salvia divinorum principal ingredient), a potent κ-opioid natural hallucinogen, on learning and memory were investigated. Wistar rats were tested in the 8-arm radial maze, for object recognition and passive avoidance tasks for spatial, episodic, and aversive memory. Attention was assessed using a latent inhibition task. Salvinorin A (80-640 μg/kg subcutaneous [sc]) did not affect short-term memory, but it impaired spatial long-term memory. Episodic and aversive memories were impaired by salvinorin A (160-640 μg/kg). Memory impairment was blocked by the selective κ-opioid receptor antagonist, nor-binaltorphimine ([nor-B]; 0.5-1 mg/kg, intraperitoneal [ip]). Salvinorin A (160 μg/kg) disrupted latent inhibition, after LiCl treatment, such as reduced sucrose intake, suggesting an attention would result in an impairment of cognitive behavior. These findings demonstrate for the first time that salvinorin A has deleterious effects on learning and memory, through a κ-opioid receptor mechanism.