Electroencephalographic and behavioral assessment of intracerebroventricular somatostatin and a substance P analogue.

Chronically implanted rats were injected either with somatostatin (SST) lumbar intrathecally (i.t.) (100 micrograms, n = 5), into the fourth ventricle (3 micrograms, n = 5; 10 micrograms, n = 6; 30 micrograms, n = 5) or into the lateral ventricle (10 micrograms, n = 6; 30 micrograms, n = 6), or received an injection of the substance P (SP) analogue, [D-Pro2, D-Trp7,9]SP into the fourth ventricle (0.3 micrograms, n = 2; 1 micrograms, n = 4; 3 micrograms, n = 4; 10 micrograms, n = 1) or lateral ventricle (3 micrograms, n = 3). A dose-dependent EEG depressant effect was observed following fourth and lateral ventricular injections of SST and of the SP analogue. Acute death due to respiratory depression was observed following i.t. and fourth ventricular injection of SST, and fourth ventricular injection of the SP analogue. Prominent motor behavior (barrel rotation, circling, cranial stereotypies) was observed, without signs of EEG seizure activity, following intraventricular injection of both drugs. Present findings indicate neurotoxic effects of SST and SP analogue at the cerebral level.