Cardiovascular and behavior changes after ICV infusion of TRH in the conscious goat.

Thyrotropin releasing hormone was infused during 5 min into the lateral brain ventricle (ICV) of conscious goats in doses ranging from 125 to 4000 ng. Changes in blood pressure, heart rate and behavior were studied. TRH in doses of 500--4000 ng raised the mean blood pressure and both the magnitude and the duration of the response was related to the dose. The onset of the rise occurred in average 8 min after the start of the infusion. The heart rate fell somewhat with all doses. No consistent changes were observed in the respiration rate. TRH caused several behavioral changes beginning about 6 min after the start of infusion. The goats often decreased their locomotor activity. They were frequently bleating except after the lowest dose. These results support the view that TRH affects several vital functions in the central nervous system.