Effects of beta-endorphin, thyrotropin-releasing hormone and cholecystokinin on body shaking behavior in rats

Effects of intracerebroventricular administration of beta-endorphin, thyrotropin-releasing hormone (TRH), cholecystokinin octapeptide (CCK-8), non-sulfated CCK-8 (CCK-8-NS) and caerulein on body shaking behavior were observed in rats. CCK-8 and its related peptides produced only a small increase in the number of body shakes, while TRH had the striking effect of stimulating body shakes, this increase being markedly suppressed by simultaneous administration of beta-endorphin. Moreover, the suppressive effect of beta-endorphin on TRH-induced body shakes was antagonized by simultaneous administration of caerulein and CCK-8. The body shakes induced by ice-water immersion were also reduced by beta-endorphin, this beta-endorphin effect being partly antagonized by caerulein and CCK-8.