The neurotropic effect of pituitary somatotropin and a fragment of it

1. Under conditions of microiontophoretic delivery to single neurons of the rat brain, pituitary somatotropin is capable of changing their electrical activity, with predominance of an inhibitory reaction. 2. When delivered to single neurons, somatotropin changes their sensitivity to the subsequent influence of exogenous norepinephrine with a sharp increase in the number of neurons activated by the monoamine. 3. The neurotropic (neuromodulatory) effect characteristic of somatotropin is reproduced by its short fragment 77–107.