The research progress on the mechanism of adenosine A1 receptor-mediated calcitonin gene-related peptide to relieve migraine

Currently, the pathogenesis of migraine is unclear. The trigeminal vascular reflex theory is the dominant pathogenesis theory, and its core parts are neurogenic inflammation and pain sensitisation. Calcitonin gene related peptide (CGRP) is the most powerful vasodilating peptide in brain circulation. It is also a marker of trigeminal nerve microvascular activation that plays a synergistic role in the pathogenesis of migraine. Adenosine A1 receptor (A1R) can inhibit the release of CGRP in the trigeminal nerve vascular system to alleviate migraine by mediating adenosine. This review summarises the progress of research on the alleviation of migraine by using A1R-mediated CGRP.

Cardiovascular reflexes following lesions in medullary reticular formation

In 19 anesthetized cats acute destruction of large portions of the medullary reticular formation was achieved with the aid of a radio-frequency lesion maker. Midline structures were spared by confining the lesions to the dorsolateral medulla. Tissue injury extended from a level rostral to the inferior olivary complex to the obex. These lesions in the medullary vasomotor area did not alter significantly the cardiovascular reflex adjustments to bilateral occlusion of the carotid arteries or to the stimulation of the central end of the cut sciatic nerve. In addition, an increase in contractile force, heart rate, and blood pressure evoked by stimulation of pressor areas in the posterior hypothalamus could be obtained following the lesions. The preparations were critically dependent upon supramedullary connections to maintain vascular tone and circulatory reflex adjustments, for decerebration in the lesioned animal brought about a reduction in blood pressure and a loss of vascular reflex responses. These findings suggest that supramedullary centers exert tonic as well as phasic influences on vascular and cardiac activity that is independent of the medullary vasomotor area.

Supraspinal inhibition of a cutaneous vascular reflex in the cat

In cats anesthetized with chloralose-urethane mixture, stimulation of an afferent nerve evoked a vasoconstrictor reflex (VCR) and a galvanic skin response (GSR) in the pads of the feet. Stimulation of the ventromedial medullary reticular substance at the level of the obex abolished the VCR and the GSR. VCR could also be reduced by occlusion during prolonged stimulation of another spinal or visceral afferent pathway. Medulla stimulation was effective without itself causing a sympathetic discharge to the paw, showing that inhibition rather than occlusion was operative. Anterior cerebellar stimulation also inhibited the VCR. Carotid sinus nerve stimulation did not abolish the VCR. It is concluded that the effective mechanism includes a bulbospinal inhibitory path projecting on a spinal vasoconstrictor reflex arc. This arrangement is similar to the descending pathways inhibiting other spinal reflexes but the VCR-inhibitory path can be activated independently of them.