Biological bases for the integration of appetitive and consummatory grooming behaviors in the cat: a review.

Cats with pontile lesions, frontal neocortical lesions, and thyroidectomized cats display a dissociation of the appetitive and consummatory components of grooming behavior following tactile stimulation of the body surface, an abnormal behavior which waxes and wanes with the seasons of the year. Tryptophan hydroxylase activity and serotonin levels were significantly decreased in the superior colliculi (but not other brain regions) in cats with pontile lesions or frontal neocortical lesions, but not in thyroidectomized cats. Systemic administration of 5-hydroxytryptophan or monoamine oxidase inhibition plus tryptophan administration abolishes the abnormal grooming behavior in each group of cats, and microinjections of 5-hydroxytryptophan or serotonin into the superior colliculi has the same effect, indicating that the change in a serotonergic system is a critical aspect of the abnormal behavior in cats with lesions and that a serotonergic system may also be involved in the genesis of the abnormal grooming behavior in thyroidectomized cats. Functional inactivation of the serotonergic system by p-chlorophenylalanine, LSD, or serotonin receptor blockade does not induce the abnormal grooming behavior in normal cats, indicating that other factors are involved. Cats with lesions and thyroidectomized cats display a rhythmic dysfunction in the excretion of glucocorticoids and glucocorticoid administration abolishes the abnormal grooming behavior, suggesting that glucocorticoids are the other critical factor. Adrenalectomized cats do not display the abnormal grooming behavior, but when adrenalectomized cats are treated with p-chlorophenylalanine, the abnormal behavior appears. Thus, a serotonergic system in the superior colliculi, operating at some level of glucocorticoid function, is involved in the integration of appetitive and consummatory grooming behaviors.