Role of thyroid hormones in an abnormal grooming behavior in thyroidectomized cats and cats with pontile lesions.

Abstract

Thyroidectomized cats and cats with pontile lesions exhibit the same abnormal grooming behavior. Investigations were conducted to determine whether the abnormal grooming behavior in cats with pontile lesions was attributable to a hypothyroid condition. Administration of thyroid hormones abolished the abnormal behavior of thyroidectomized cats but was without effect in cats with pontile lesions. Studies of brain and blood levels of thyroid hormones in cats with pontile lesions failed to detect any differences from normal cats, and normal effects of thyroid hormones on evoked potentials to light flashes and to clicks were obtained in cats with pontile lesions. It was concluded that any thyroid dysfunction that may exist in the cats with pontile lesions was not involved in the genesis of the abnormal grooming behavior. Because the abnormal grooming behavior fluctuates rhythmically during the year, an endocrine hypothesis was entertained as the source of the fluctuations; endocrine concomitants of the abnormal behavior were investigated with longitudinal studies. The urinary excretion of 11hydroxycorticoids exhibited a significant negative correlation with the abnormal behavior. When compared with that of normal cats, the plasma level of 11-hydroxycorticoids of thyroidectomized cats was significantly decreased. Intramuscular injections of 11-hydroxycorticoids abolished the abnormal behavior in both thyroidectomized cats and cats with pontile lesions. These results considered together with previous findings indicate that thyroidectomy and pontile lesions induce similar changes in 11-hydroxycorticoid and serotonergic functions-changes that are critical features of the physiological bases of the abnormal grooming behavior in both groups.After pontile lesions, consummatory mally directed to the part of the body surface grooming behaviors of the cat are elicited that is tactually stimulated (complete deby tactile stimulation. The normally pre-tails are given by Randall, 1964). Thus the ceding appetitive components of the be-lesion induces an elicitable disintegration of havior do not occur. When you touch a cat the appetitive and consummatory componwith a pontile lesion on the back, the con-ents of grooming behavior. The importance summatory grooming behavior that is nor-of the appetitive-consummatory dichotomy mally directed to the back, the scratching was recognized by Sherrington (1906, pp. bite, is emitted immediately, occurring in 326 ff.) and first systematically studied by midair and thus with no adaptive or func-Craig (1918). More recent analyses of betional role. The consummatory response havior in these terms include the work of that is emitted is the response that is nor-Ewert Kupfermann (1974).

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

“…Several studies have reported degeneration of the adrenal cortex in hypothyroid animals (e.g., Johansson & Jonsson, 1966), and significant decreases in the size of the zona fasciculata, which secretes glucocorticoids, have been found in hypothyroid animals (Johansson & Jonsson, 1971). Measurements of 11-hydroxycorticoids in our thyroidectomized cats indicate a significant decrease (Randall et al, 1976). Thus, thyroidectomy induces one of the deficits that is essential for the induction of the abnormal grooming behavior.…”

“…The fact that PCPA administration induces grooming fragments in cats with pontile or frontal neocortical lesions (Trulson, 1976b;Trulson & Randall, 1973) and in thyroidectomized cats (Table 1) is further evidence for a similar mechanism. In addition, the superior colliculi are implicated in all three groups, and identical seasonal patterns of change in the areal extent of the grooming fragments occur in each group of cats (Randall & Parsons, 1972;Randall et al, 1976;Trulson, 1976b). Variations in levels of serotonin may be responsible for the seasonal variation in the abnormal behavior.…”

“…Thus, the situation is complex and rhythmic variations in the activity either of the serotonergic system or of the adrenal cortex (or the rhythmic interactions of the two) may account for the spontaneous reversions of the abnormal grooming behavior. It is clear (a) that decreased serotonin and glucocorticoids are necessary and sufficient conditions for inducing the abnormal grooming behavior (Trulson, 1976a) and (b) that either exogenous 5-HTP (Trulson, 1976a;Trulson & Randall, 1973; see Table 1) or exogenous glucocorticoids (Randall et al, 1976; are sufficient to abolish the abnormal grooming behavior. In conclusion, there appears to be a similar mechanism for the mediation of the abnormal grooming behavior in all groups of cats studied, and this mechanism involves serotonin, glucocorticoids, and the superior colliculus.…”

“…The degree of the abnormal grooming behavior, in terms of the percentage of the body surface from which the grooming fragments can be elicited, varies spontaneously with the seasons of the year in each group of cats (Randall & Parsons, 1972;Randall, Trulson, & Parsons, 1976). The abnormality is most pronounced during the fall of the year, and an abnormal behavioral trough occurs during the summer.…”

“…That another factor is involved is indicated by the failure of systemic or local (superior colliculi) injections of PCPA to induce the abnormal grooming behavior in normal cats (Trulson et al, 1975;Trulson & Randall, 1973). The other factor is decreased glucocorticoid levels: There is an inverse relation between glucocorticoid excretion and the percentage of the body surface from which grooming fragments can be elicited in cats with pontile lesions, and systemic administration of glucocorticoids abolishes the abnormal grooming behavior in cats with pontile (Randall, Trulson, & Parsons, 1976) or frontal neocortical lesions . While adrenalectomized cats do not display grooming fragments, administration of PCPA to adrenalectomized cats induces the same kind of abnormal grooming behavior that is found in cats with pontile or frontal lesions (Trulson, 1976a).…”