Rapamycin suppresses PTZ-induced seizures at different developmental stages of zebrafish.

The mTORC1 complex integrates different inputs from intracellular and extracellular signals to control various cellular processes. Therefore, any disruption in the mTORC1 pathway could promote different neurological disorders. mTORC1 overactivation has been verified in different genetic and acquired epilepsy animal models. Therefore, inhibitors of this complex could have both antiepileptogenic and antiseizure effects. In our study, we investigated the effects of rapamycin pretreatment on pentylenetetrazole (PTZ)-induced seizures in zebrafish. Our results have shown that the latency to reach the tonic-clonic stage (stage III) of progressive behavioral alterations shown during PTZ-induced seizures was prolonged in larval (7days post fertilization, 7dpf), juvenile (45days post fertilization, 45dpf) and adult (6-8months) zebrafish after pretreatment with rapamycin. Furthermore, rapamycin pretreatment did not alter the locomotor activity in zebrafish. Therefore, the results obtained in our study indicate that rapamycin pretreatment is an important mechanism to control the progress of seizures in zebrafish throughout different developmental stages (larval, juvenile, and adult). Taken as a whole, our data support that rapamycin has immediate antiseizure effects and could be a potential alternative therapy for seizure control in epilepsy.

Role of adenosine signaling on pentylenetetrazole-induced seizures in zebrafish.

Adenosine is a well-known endogenous modulator of neuronal excitability with anticonvulsant properties. Thus, the modulation exerted by adenosine might be an effective tool to control seizures. In this study, we investigated the effects of drugs that are able to modulate adenosinergic signaling on pentylenetetrazole (PTZ)-induced seizures in adult zebrafish. The adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) decreased the latency to the onset of the tonic-clonic seizure stage. The adenosine A1 receptor agonist cyclopentyladenosine (CPA) increased the latency to reach the tonic-clonic seizure stage. Both the adenosine A2A receptor agonist and antagonist, CGS 21680 and ZM 241385, respectively, did not promote changes in seizure parameters. Pretreatment with the ecto-5'nucleotidase inhibitor adenosine 5'-(α,ß-methylene) diphosphate (AMPCP) decreased the latency to the onset of the tonic-clonic seizure stage. However, when pretreated with the adenosine deaminase (ADA) inhibitor, erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA), or with the nucleoside transporter (NT) inhibitors, dipyridamole and S-(4-Nitrobenzyl)-6-thioinosine (NBTI), animals showed longer latency to reach the tonic-clonic seizure status. Finally, our molecular analysis of the c-fos gene expression corroborates these behavioral results. Our findings indicate that the activation of adenosine A1 receptors is an important mechanism to control the development of seizures in zebrafish. Furthermore, the actions of ecto-5'-nucleotidase, ADA, and NTs are directly involved in the control of extracellular adenosine levels and have an important role in the development of seizure episodes in zebrafish.