SUBDIAPHRAGMATIC VAGOTOMY DOES NOT PREVENT THE ANTI-EXPLORATORY EFFECT OF CERULEIN IN THE ELEVATED PLUS-MAZE

We compared the action of subdiaphragmatic vagotomy upon the anti-expl oratory and motor depressant effects of caerulein, an agonist of chole cystokinin (CCK) receptors, in male rats. Vagotomized rats entered mor e frequently into the open arms of elevated plus-maze compared to inta ct control rats, Caerulein (1 mug/kg subcutaneously (s.c.)) significan tly suppressed the exploratory behaviour in vagotomized rats but not i n intact and sham-operated rats. In contrast, subdiaphragmatic vagotom y did not change the locomotor activity of rats in open field compared to intact and sham-operated animals. At a higher dose (10 mug/kg s.c. ), the caerulein pretreatment markedly decreased the number of line cr ossings, rearings and head-dippings of intact animals in open field. I n sham-operated rats caerulein also suppressed the locomotor activity, whereas in vagotomized rats it only tended to reduce the frequency of rearings. Consequently, the present study revealed the different acti on of vagotomy upon the motor depressant and anti-exploratory effects of caerulein. These results support the view that CCK(A) receptors in the gastrointestinal tract are mediating the motor depressant, whereas CCK(B) receptors in the brainstem are involved into the mediation of anti-exploratory effect of caerulein.