ABSTRACT
The pontine-medullary noradrenergic (NE) cell groups are the source of hypothalamic and spinal norepinephrine. The action of this neurotransmitter at central level augments or decreases peripheral sympathetic activity which is dependent on: NE released from sympathetic nerves and norepinephrine + epinephrine released from adrenal glands. The pontine NE nucleus, locus coeruleus, has a widely spread terminal distribution covering almost the entire central nervous system including the cerebral cortex, hippocampus, cerebellum, hypothalamus, medulla oblongata, pontis, and spinal cord. Adrenal catecholamines are released by the adrenal glands. These glands receive two kinds of excitatory inputs, one cholinergic and the other β-adrenergic. Other studies show that cardiovascular responses to acetylcholine can be initiated in a number of cardiovascular loci situated at various levels of the rat brain. Apparently, the cardiovascular loci of all these brain areas possess muscarinic cholinoceptors mediating pressor responses, as well as those mediating depressor responses, but not in equal proportion.
