Studies of somatostatin-induced barrel rotation in rats.

Somatostatin (SRIF) has been reported to induce abnormalities of motor behavior in rats when injected intraventricularly. Following an injection, non-lesioned rats develop unilateral extension of the limbs, a twist about the long axis, and repeated lateral rolling, called "barrel rotation". It has not been clear whether this behavior is due to a pharmacologic action of SRIF, such as an effect of SRIF on systems of motor control. Prior reports observed the response only at high doses of SRIF, and found no dose-response relationship for it. We have investigated whether this response is due to a pharmacologic effect of SRIF. We have also studied where SRIF acts, when injected intraventricularly, to induce this response. We have found that SRIF-induced rotation increases linearly with doses up to 10 micrograms and thereafter declines. Biologically inactive analogues of SRIF did not induce barrel rotation. Dose-response studies of intraventricular and intracerebral microinjections indicated that SRIF acts at the vestibular nuclear complex (VNC) to induce rotation. At VNC, 0.25 micrograms SRIF produced postural abnormalities. We conclude that barrel rotation is due to a pharmacologic action of SRIF, and that SRIF does act upon a system of motor control, the VNC, to induce this response.