Raphe lesions and 5,7-dihydroxytryptamine induce grooming reflexes in adrenalectomized cats

Grooming reflexes are induced by frontal neocortical, pontile, or spinal lesions in dogs and cats. In intact cats, the combined treatments of adrenalectomy and para-chlorophenylalanine administration induce grooming reflexes. Two other ways of depleting serotonin (with 5,7-dihydroxytryptamine and raphe lesions) were combined with adrenalectomy in the present study as further tests that serotonin and glucocorticoid hormones are the critical factors in the induction of grooming reflexes. Because the deficit in serotonin is confined to the superior colliculi in cats with frontal and pontile lesions, 5,7-dihydroxytryptamine (5,7-DHT) was injected directly into the superior colliculi at eight sites, 2 microgram/site (1 microliter at .5 microliter/min). Electrolytic dc lesions of the dorsal and superior central raphe nuclei were made in another group, and then both groups were adrenalectomized. There were three control groups: (a) a group with vehicle injections in the superior colliculi and laporatomies, (b) a group with 5,7-DHT injections in the superior colliculi, and (c) a group with the raphe lesions. Large receptive fields for grooming reflexes occurred only in the groups with combined treatments. Thus the mechanism of induction of grooming reflexes by central nervous system lesions involves independent changes in a hormonal and a neurotransmitter system which combine to effect the change in behavior.