Microinjection of GABAergic agents into the anterior nucleus of the thalamus modulates pilocarpine-induced seizures and status epilepticus

Location of the cannulae used for microinjecting GABAergic agents into the anterior nucleus of the thalamus (AN). Schematic representation of the tips of the cannulae though which 0.5μl of muscimol 160nmol (), muscimol 80nmol (), or bicuculline () were successfully injected within the AN (reprinted from Ref. 16; p. 23–26; Copyright (1998) with permission from Elsevier). Cannulae placement in animals receiving 0.2μl injections was similar to that represented in this figure.

GABAergic agents microinjected into the anterior nucleus of the thalamus (AN) influence the development of pilocarpine-induced seizures and status epilepticus (SE). (A and B) Animals receiving AN 160nmol muscimol 0.5μl injections (n=6) had a significantly increased latency to seizures and SE as compared to controls (n=8; p<0.001 and p=0.01). In contrast, 80nmol muscimol injections (n=6) were not protective, whereas AN bicuculline (n=5) was proconvulsant. (C) No significant differences were observed in the percentage of animals developing SE across groups. Lines on top of the bars represent standard deviations. *Statistically significant.

Latency for pilocarpine-induced seizures and status epilepticus (SE) in animals treated with anterior thalamic nucleus (AN) or ventricular 0.2μl muscimol injections. (A and B) Animals receiving AN 160nmol muscimol (n=11) had a significantly increased latency to seizures and SE as compared to controls (n=10; p<0.01 and p=0.02). (C) In contrast, injections of 64–80nmol (n=4) or 100–120nmol (n=4) of ventricular muscimol were not protective. Lines on top of the bars represent standard deviations. *Statistically significant.

Electrographic activity recorded in the cerebral cortex after pilocarpine treatment. EEG tracings showing the onset of a generalized seizure in animals treated with bilateral AN injections of saline (upper trace in A) or muscimol 160nmol (upper trace in B). In both groups, status epilepticus was characterized by continuous high-voltage fast spiking activity (lower traces in A and B). Vertical scale bar, 100mV; horizontal scale bar, 5s.