VAGAL CONTROL OF LYMPHOCYTE RELEASE FROM RAT THYMUS

The effects of the efferent vagal innervation on the thymus gland of t he rat were investigated in vivo by means of section and stimulation e xperiments. It has been shown that section of the right vagus produces a decrease in the number of lymphocytes released from the thymus into the venous circulation, an effect that disappears after section of th e recurrent laryngeal nerve. Vagal stimulation produces a transient in crease in the number of lymphocytes released from the thymus, an effec t that also disappears after section of the recurrent nerve. The effec ts of vagotomy are mimicked by nicotinic blocking agents, which also s uppress the effects of vagal stimulation, whereas muscarinic blocking agents were ineffective. It is concluded that the vagal fibres running in the recurrent laryngeal nerve exert a tonic and phasic facilitator y influence on the mechanisms responsible for lymphocyte release from the thymus, and that this action is mediated through nicotinic recepto rs.