[Neurotropic effect of hypophyseal somatotropin and its fragment]

The effect of sei whale somatotropin and its biologically active fragment 77-107 (under conditions of microionophoresis) on the cortical, caudate nucleus and amygdala single neuron electrical activity of the rat brain as well as on the neuron sensitivity to noradrenaline was studied. The neurons, responded to somatotropin and its fragment inhibitory action, were revealed in all the brain regions examined. The majority of neurons did not react to noradrenaline, part of them responded to noradrenaline, decreasing the impulse activity and a very small part--increased the impulse effect. The preliminary use of somatotropin or its fragment sharply increased the number of noradrenaline-activated neurons. The data obtained indicate that somatotropin exhibits the neurotropic (neuromodulative) activity, preserved by its fragment 77-107. This effect may be caused by the initial somatotropin and its fragment capacity to increase phosphodiesterase-produced catalyzing cAMP destruction in some neural structures.