[Central autonomic mechanism and neurotransmitters].
Neurotransmitters involved in the central regulation of the autonomic function have, to some extent, been elucidated. Substance P, adrenaline and glutamate neurons originating from the rostral ventrolateral medulla oblongata (VLM) produce a tonic excitation of sympathetic preganglionic neurons. The A1 noradrenaline neurons in the caudal VLM inhibit sympathetic activity by inhibiting neurons in the rostral VLM. In the dorsal medulla, the baroreceptor afferents with substance P converge to the adrenaline-neuropeptide Y (NPY) interneurons located in the dorsal strip of the nucleus tractus solitarius (NTS). These interneurons suppress neuronal activity of the A2 noradrenaline neurons, a vasopressor system, by interacting with alpha 2-adrenergic and NPY receptors. The area postrema, a circumventricular organ devoid of the blood-brain barrier, has access to regulatory information of blood-borne angiotensin II and atrial natriuretic peptide at specific receptors on the neuronal elements. The information is then transmitted to the NTS and dorsal motor nucleus of the vagus. Studies focusing on the physiological and pharmacological profiles of neurotransmitters are expected to enhance our knowledge of the central regulation of the autonomic function.