Similarities in the physiological bases of an abnormal grooming behavior in thyroidectomized cats and in cats with lesions of the central nervous system.

Thyroidectomized cats display a dissociation of the appetitive and consummatory components of grooming behavior when the body surface is tactually stimulated, an abnormal behavior that also occurs in cats with pontile or frontal neocortical lesions. Systemic administration of 5-hydroxytryptophan (5-HTP) abolishes the abnormal behavior, whereas dihydroxyphenylalanine administration does not, and p-chlorophenylalanine (PCPA) administration induces the abnormal grooming behavior in thyroidectomized cats that are not displaying the abnormal behavior because of spontaneous seasonal reversions. Microinjections of 5-HTP or serotonin into the superior colliculi also abolish the abnormal grooming behavior in thyroidectomized cats. Lesions of the superior colliculi prevent the development of the abnormal behavior after thyroidectomy, even with PCPA treatment. These pharmacological results in thyroidectomized cats parallel the behavioral effects observed in cats with pontile or frontal neocortical lesions.