Central nervous system structures connected with the endocrine glands. findings obtained with the viral transneuronal tracing technique.

This review is a summary of recent neuromorphological observations on the existence of multisynaptic neural pathways between the endocrine glands and the central nervous system (CNS) and its structures involved in this pathway. Introduction of the viral transneuronal tracing technique has made possible investigations of multisynaptic connections. The utility of this approach is based on the ability of the neurotropic virus to invade and replicate in neurons, and then gradually infect synaptically linked second-order, third-order. etc. neurons. Injecting the virus into the endocrine glands, this technique was used to identify cell groups in the spinal cord and in the brain which are connected with the adrenal gland, the gonads and the pancreas. Injection of the virus into these organs resulted in viral labeling of neurons in practically identical structures of the CNS including the intermediolateral cell column of the spinal cord, the vagal nuclei and certain other cell groups in the brain stem. In the hypothalamus the most intensive labeling was in the parvocellular part of the paraventricular nucleus and in the telencephalon labeled nerve cells were detected in the amygdala, the bed nucleus of the stria terminalis and in the preoptic area. It is known that the labeled CNS structures are members of descending pathways arising from the hypothalamic paraventricular nucleus or from other cell groups and terminating on neurons of the vagal nuclei and the intermediolateral cell column of the spinal cord. Experimental data support the view that the CNS structures and pathways connected with the endocrine glands are involved in the neural control of these organs.