Ischemic stroke is characterized by the sudden interruption of blood flow to the brain, leading to the death of neuronal cells in the affected area. When this condition affects areas related to the visual circuit, it often results in defects of the visual field. The aim of this study is to explore a potential treatment to improve altered visual conditions resulting from ischemic stroke at the levels of the visual cortex. A photothrombotic model was used to induce ischemic stroke in the V1 visual cortex of Thy1GFP mice. Animals were then treated with a dose of 0.05 mg/kg of the drug KKR8 a 5-HT2A receptor. Thi receptor is known to be involved in neuroplasticity and dendritic spine genesis mechanisms. Four different experimental groups were studied: one not subjected to stroke and treated with saline solution (no stroke vehicle, n=12), a second one subjected to stroke and also treated with saline solution (stroke vehicle, n=10), one subjected to stroke and treated with the drug starting 24 hours after the event (stroke KKR8, n=10), and a final one subjected to stroke and initially treated with saline solution then treated with the drug after 14 days from the stroke (stroke vehicle + KKR8, n=10). This last experimental group was used to assess the effects of the drug with a treatment starting when spontaneous repair processes had already started. After 45 days of treatment with KKR8, the visual abilities of the animals were evaluated through behavioral pharmacology tests. The study did not reveal any signs of toxicity associated with the treatment, and an improved performance was observed in the stroke KKR8 group in some of the behavioral tests. The visual cliff test evaluates depth perception based on an optical illusion. The speed of the animals within the less secure zone of the apparatus was considered: the animals in the stroke KKR8 group showed a speed similar to the no stroke vehicle group (P>0.999). In contrast, the animals in the stroke vehicle + KKR8 group showed a lower speed than the no stroke vehicle group (P=0.0129). The looming visual stimuli test assesses the visual abilities of animals using a visual stimulus that mimics a predator attack. The animals in the stroke KKR8 group displayed a greater flight response and a longer freezing time compared to both the stroke vehicle group (P=0.040 and P=0.0483, respectively) and the stroke vehicle + KKR8 group (P=0.025 and P=0.0115, respectively). The number of entries into the safe zone of the apparatus in the stroke KKR8 group was greater than in the stroke vehicle group (P=0.018) and similar to the no stroke vehicle group. Both the stroke vehicle group (P=0.0004) and the stroke vehicle + KKR8 group (P=0.0070) showed a longer latency to enter the safe zone compared to the no stroke vehicle group, whereas the stroke KKR8 group exhibited a similar latency (P=0.2225). In the cued Morris water maze test, learning is assessed by having the animals to identify a hidden platform placed in a pool based on the presence of visual stimulus. The number of times the animal reaches the platform during 3 consecutive days was evaluated. Interestingly, on the first day of testing, the stroke KKR8 group, but not the stroke vehicle + KKR8 group, reached the platform a greater number of times than the stroke vehicle group (P=0.0373). Overall, this study suggests that treatment with KKR8 initiated 24 hours after the induction of ischemic stroke is well-tolerated and can improve visual abilities to levels similar to those of animals without stroke. In contrast, when the treatment begins after spontaneous repair processes have already occurred, the drug's effects on visual improvement appear to be not significant.
L’ictus ischemico è caratterizzato dall’interruzione improvvisa del flusso sanguigno a livello cerebrale che provoca la morte delle cellule neuronali dell’area colpita. Quando questa patologia colpisce aree legate al circuito visivo spesso risulta in difetti all’interno del campo visivo stesso. L’obiettivo di questo studio è quello di esplorare un possibile trattamento per migliorare le condizioni visive alterate conseguenti ad ictus ischemico a livello delle aree del circuito visivo. È stato utilizzato il modello fototrombotico per indurre ictus ischemico a livello della corteccia visiva V1 in topi Thy1GFP che sono poi stati trattati con una dose 0,05 mg/Kg di farmaco KKR8, un agonista del recettore 5-HT2A il quale è noto per essere coinvolto in meccanismi di neuroplasticità e spinogenesi. Sono stati studiati quattro diversi gruppi sperimentali: uno non sottoposto ad ischemia e trattato con soluzione salina (no stroke vehicle, n=12); un secondo sottoposto ad ischemia e trattato con soluzione salina (stroke vehicle, n=10); uno sottoposto ad ischemia e trattato, a partire da 24 ore dopo l’evento, con il farmaco KKR8 (stroke KKR8, n=10); e un ultimo sottoposto ad ischemia e trattato prima con soluzione salina e poi, dopo 14 giorni, con il farmaco KKR8 (stroke vehicle + KKR8, n=10). Quest’ultimo gruppo sperimentale è stato utilizzato per valutare gli effetti del farmaco in caso di un inizio tardivo del trattamento, cioè quando i processi di riparazione spontanea sono già stati messi in atto. Dopo 45 giorni di trattamento le abilità visive degli animali sono state valutate tramite test di farmacologia comportamentale. Dallo studio non sono emersi segni di tossicità dovuti al trattamento ed è stata osservata invece una performance migliore da parte del gruppo stroke KKR8 in alcuni dei test. Il visual cliff test valuta la percezione della profondità basandosi su un’illusione ottica. Gli animali del gruppo stroke KKR8 mostrano una velocità all'interno della zona meno sicura dell'apparato simile a quella del gruppo no stroke vehicle (P>0.999) al contrario degli animali del gruppo stroke vehicle + KKR8 che invece mostrano una velocità minore (P=0.0129). Il looming visual stimuli test valuta le abilità visive degli animali simulando l’attacco di un predatore. Gli animali del gruppo stroke KKR8 mostrano una maggiore risposta di flight e un più alto tempo di freezing sia rispetto al gruppo stroke vehicle (rispettivamente P=0.040 e P=0.0483) che rispetto al gruppo stroke vehicle + KKR8 (rispettivamente P=0.025 e P=0.0115). Il numero di animali del gruppo stroke KKR8 che entra nella zona sicura dell’apparato è maggiore rispetto a quello del gruppo stroke vehicle (P=0.018) e simile a quello del gruppo no stroke vehicle. Inoltre, sia il gruppo stroke vehicle (P=0.0004) che il gruppo stroke vehicle + KKR8 (P=0.0070) mostrano una latenza all’ingresso nella zona sicura superiore a quella del gruppo no stroke vehicle mentre il gruppo stroke KKR8 mostra una latenza simile (P=0.2225). Nel cued Morris water maze test si valuta l’apprendimento facendo identificare agli animali una piattaforma nascosta all’interno di una piscina sulla base della presenza di uno stimolo visivo. È stato valutato il numero di volte in cui l’animale raggiunge la piattaforma durante 3 giorni consecutivi di test. È di interesse notare che il primo giorno di test il gruppo stroke KKR8, ma non il gruppo stroke vehicle + KKR8, ha raggiunto la piattaforma un numero di volte superiore rispetto al gruppo stroke vehicle (P=0.0373). Lo studio mostra che il trattamento con KKR8 iniziato 24 ore dopo l’induzione di un ictus ischemico è ben tollerato e può migliorare le abilità visive fino a livello simili a quelli di animali senza ischemia. Se il trattamento inizia quando i processi di riparazione spontanea hanno già avuto luogo gli effetti del farmaco sul miglioramento visivo sembrano non essere altrettanto significativi.
Valutazione in-vivo degli effetti di un agonista del recettore 5-HT2A in un modello murino di ictus ischemico a livello della corteccia visiva
BARZON, BENEDETTA
2022/2023
Abstract
Ischemic stroke is characterized by the sudden interruption of blood flow to the brain, leading to the death of neuronal cells in the affected area. When this condition affects areas related to the visual circuit, it often results in defects of the visual field. The aim of this study is to explore a potential treatment to improve altered visual conditions resulting from ischemic stroke at the levels of the visual cortex. A photothrombotic model was used to induce ischemic stroke in the V1 visual cortex of Thy1GFP mice. Animals were then treated with a dose of 0.05 mg/kg of the drug KKR8 a 5-HT2A receptor. Thi receptor is known to be involved in neuroplasticity and dendritic spine genesis mechanisms. Four different experimental groups were studied: one not subjected to stroke and treated with saline solution (no stroke vehicle, n=12), a second one subjected to stroke and also treated with saline solution (stroke vehicle, n=10), one subjected to stroke and treated with the drug starting 24 hours after the event (stroke KKR8, n=10), and a final one subjected to stroke and initially treated with saline solution then treated with the drug after 14 days from the stroke (stroke vehicle + KKR8, n=10). This last experimental group was used to assess the effects of the drug with a treatment starting when spontaneous repair processes had already started. After 45 days of treatment with KKR8, the visual abilities of the animals were evaluated through behavioral pharmacology tests. The study did not reveal any signs of toxicity associated with the treatment, and an improved performance was observed in the stroke KKR8 group in some of the behavioral tests. The visual cliff test evaluates depth perception based on an optical illusion. The speed of the animals within the less secure zone of the apparatus was considered: the animals in the stroke KKR8 group showed a speed similar to the no stroke vehicle group (P>0.999). In contrast, the animals in the stroke vehicle + KKR8 group showed a lower speed than the no stroke vehicle group (P=0.0129). The looming visual stimuli test assesses the visual abilities of animals using a visual stimulus that mimics a predator attack. The animals in the stroke KKR8 group displayed a greater flight response and a longer freezing time compared to both the stroke vehicle group (P=0.040 and P=0.0483, respectively) and the stroke vehicle + KKR8 group (P=0.025 and P=0.0115, respectively). The number of entries into the safe zone of the apparatus in the stroke KKR8 group was greater than in the stroke vehicle group (P=0.018) and similar to the no stroke vehicle group. Both the stroke vehicle group (P=0.0004) and the stroke vehicle + KKR8 group (P=0.0070) showed a longer latency to enter the safe zone compared to the no stroke vehicle group, whereas the stroke KKR8 group exhibited a similar latency (P=0.2225). In the cued Morris water maze test, learning is assessed by having the animals to identify a hidden platform placed in a pool based on the presence of visual stimulus. The number of times the animal reaches the platform during 3 consecutive days was evaluated. Interestingly, on the first day of testing, the stroke KKR8 group, but not the stroke vehicle + KKR8 group, reached the platform a greater number of times than the stroke vehicle group (P=0.0373). Overall, this study suggests that treatment with KKR8 initiated 24 hours after the induction of ischemic stroke is well-tolerated and can improve visual abilities to levels similar to those of animals without stroke. In contrast, when the treatment begins after spontaneous repair processes have already occurred, the drug's effects on visual improvement appear to be not significant.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/16749