Effects of neural stalk stimulation on phasic discharge of supraoptic neurones in Brattleboro rats devoid of vasopressin.

Brattleboro rats, homozygous for diabetes insipidus, and Long-Evans rats were anaesthetized with urethane, and antidromically identified neurons were recorded from the supraoptic nucleus. Phasically firing neurones were studied during repeated electrical stimulation of the neural stalk, whereby most supraoptic neurones, but not the recorded neurone, were activated antidromically. Such stimulation consistently modified the discharge pattern of phasic neurones in Long-Evans rats, but was relatively ineffective in Brattleboro rats. These results suggest that the effects of neural stalk stimulation on discharge patterns in Long-Evans rats may be substantially mediated by the evoked release of vasopressin or neurophysin.