IS THE CUNEIFORM NUCLEUS A CRITICAL COMPONENT OF THE MESENCEPHALIC LOCOMOTOR REGION - AN EXAMINATION OF THE EFFECTS OF EXCITOTOXIC LESIONS OF THE CUNEIFORM NUCLEUS ON SPONTANEOUS AND NUCLEUS-ACCUMBENS INDUCED LOCOMOTION

The cuneiform nucleus and the pedunculopontine tegmental nucleus have both been suggested as possible sites for the mesencephalic locomotor region (MLR), an area from which controlled stepping on a treadmill ca n be elicited following electrical or chemical stimulation in a decere brate animal, It has been shown that excitotoxic lesions of the pedunc ulopontine tegmental nucleus impair neither spontaneous locomotion nor locomotion induced by stimulation of the nucleus accumbens. Excitotox ic lesions of the cuneiform nucleus have not previously been investiga ted, Rats received either bilateral ibotenate or sham lesions of the c uneiform nucleus combined with bilateral implantation of guide cannula e aimed at the nucleus accumbens, On recovery from surgery spontaneous locomotion was tested, followed by accumbens-stimulated locomotion. F or nucleus accumbens stimulation, each rat received bilateral microinj ection of each of three doses of d-amphetamine (10.0, 20.0 and 30.0 mu g) and a vehicle only injection. Locomotor activity was recorded foll owing the injection. In comparison to the sham-lesioned group, the ibo tenate-lesioned group showed no differences in either spontaneous or a mphetamine-induced locomotor activity. These results suggest that, lik e the pedunculopontine tegmental nucleus, the cuneiform nucleus is not involved in the direct mediation of spontaneous or accumbens-induced locomotion, and thus is very unlikely to be the anatomical substrate o f the MLR. The role of the cuneiform nucleus in other types of behavio ural control is discussed. Copyright (C) 1996 Elsevier Science Inc.