A failure to support cross-sensitization between effects of apomorphine and lesions of the habenula nucleus

An interchangeability between the effects of stress and psychostimulants has been reported. The possible common physiological effects of lesions of the habenula, stress and psychostimulant administration of activation of ascending dopamine systems suggested examination of a cross-sensitization between lesions of the habenula and psychostimulant administration. Lesions of the habenula were found to increase baseline activity but there were no significant changes in response to apomorphine in either various categories of stereotypy or locomotor response. Lesioned rats and controls both demonstrated similar dose and time-related effects in various response measures. Although not significant, certain results suggested that changes tended to be in the direction opposite to that of the suggested sensitization. The results are contrasted with previous supporting data and discussed in terms of the potentially diverse manner in which habenular manipulation and psychostimulants may influence dopaminergic activity and subsequent behaviour.