Two days following unilateral section of the cervical vagus nerve, there was a dramatic ipsilateral increase in P2X1, P2X2, and P2X4 receptor
immunoreactivity in the cell soma of vagal efferent neurons in the dorsal vagal motor nucleus, but not in the nucleus ambiguous (72). Following
surgical sympathectomy, 28% of the spontaneously active afferent fibers in sciatic nerve responded to ATP, compared with none in intact rats
(343). After nerve injury, P2X4 receptor expression increased strikingly in hyperactive microglia, but not in neurons or astrocytes, in the
ipsilateral spinal cord; this appears to be associated with tactile allodynia (1731 and see sect. XIB9).
The sympathetic nervous system has been shown to modulate macrophage function (331), and
alterations in T- and B-lymphocyte proliferation and differentiation have been described following chemical sympathectomy (1090). Close
contacts between enteric nerves and lymphocytes in mouse intestinal mucosa and submucosa have been reported (402, 630).
Sympathetic and sensory nerves innervate bone, and sympathectomy modifies bone development and resorption (see Ref. 166). ATP, probably
released as a cotransmitter with NE, regulates Ca2+ metabolism in osteoblast-like bone cells (979). Evidence has been presented to demonstrate a
role for the sympathetic nervous system in controlling bone density via leptin that activates hypothalamic nerves, which in turn activate the
sympathetic nerves that innervate osteoblasts. ATP has been shown to inhibit bone formation by osteoblasts and to stimulate bone resorption by osteoclasts .
Physiology and Pathophysiology of Purinergic Neurotransmission
Geoffrey Burnstock
Autonomic Neuroscience Centre, Royal Free and University College Medical School, London, UnitedKingdom
