Effects of kainic acid injections in the striatum on physiologic and behavioral functions in conscious rats.

Alterations in both physiologic and behavioral functions were assessed in unanesthetized rats after a unilateral injection of kainic acid (KA) in the striatum. The immediate behavioral effects were dyskinesias, head swaying, circling, tail elevation, hyperpnea and marked salivation. The induced behavioral responses lasted for about 14 to 18 h. Rats with intrastriatal KA injection, although showing no thermoregulatory deficit at both moderate (22 degrees C) and hot (30 degrees C) environmental temperatures, displayed a lower metabolism and a lower rectal temperature than the preinjection controls in the cold (8 degrees C) environment. In addition, the hypothermia induced by intrastriatal administration of apomorphine (dopamine agonist) was greatly antagonized by pretreatment with intrastriatal injection of KA. Furthermore, intrastriatal infusions of KA (1 microgram in 0.5 microliter) also caused a decrease in pain threshold (or in the latency to the hind-paw lick on the hot plate test), hypophagia, polydipsia, and weight loss. The induced alterations in thermoregulation, pain reflex, and ingestive behavior lasted for about 7 days. These data indicate that striatal neurons are involved in the central control of motor activity, thermoregulation, the pain reflex, and ingestive behavior.