Effect of pentylenetetrazol-induced convulsions on somatostatin-like immunoreactivity in rat cerebrospinal fluid.

Somatostatin is a neuropeptide that in several experimental models of epilepsy has been suggested to modulate epileptic activity. The purpose of the present study was to investigate the role of somatostatin in seizure phenomena. We measured the somatostatin-like immunoreactivity (SLI) by radioimmunoassay of the cisternal CSF of rats. A polyethylene cannula had before-hand been inserted into the cisterna magna. Thereafter seizures were induced by pentylenetetrazol (PTZ). The nonconvulsive group of rats received a single subconvulsive dose of PTZ (30 mg/kg, i.p.). This group of rats exhibited only clonic jerks but not generalized clonic-tonic convulsion (GC). The CSF samples were taken 2 and 10 minutes after the jerks began. The convulsive group of rats received a single convulsive dose of PTZ (50 mg/kg, i.p.), and each of those animals had GC. From those rats the CSF samples were collected 5, 30, and 60 minutes and 4 and 24 h after the GC began. The values were compared with the SLI levels in controls, from which CSF was collected 10 minutes after injection of 0.9% NaCl. In the convulsion group the SLI levels increased 241% (p less than 0.01) five minutes after GC and returned to control level in 30 minutes. In the nonconvulsion group, where the rats expressed only jerks but not GC, SLI levels remained constant. These data suggest that somatostatin is released into CSF after the generalized clonic-tonic phase of the PTZ-induced convulsion.