Mechanisms Underlying Spinal Neuromodulation of the Exercise Pressor Reflex
Spinal neurotransmitters or neuromodulators can affect the afferent arm of the reflex cardiovascular response to muscle contraction (Hill and Kaufman, 1990; Hill and Kaufman, 1991) [i.e. the exercise pressor reflex]. Potentially important neuromodulators may be vasopressin, oxytocin and prostaglandin E2 (PGE2). Both oxytocin and vasopressin have been located in the spinal dorsal horn where primary sensory afferent input is received and processed (Milan et al, 1984). The origin of this oxytocin and vasopressin is cell bodies of neurosecretory neurons located in the paraventricular nucleus of the hypothalamus (Nilaver et al, 1980). These neurons project to the substantia gelatinosa (lamina II) of the dorsal horn (Nilaver et al, 1980). This area is known for processing information from group III and IV afferent nerves associated with nociception (Jessel and Jahr, 1985). A portion of these sensory fibers may also serve as ergoreceptors that evoke the exercise pressor reflex (McCloskey and Mitchell, 1972).
KeywordsMean Arterial Pressure Dorsal Horn Heart Rate Response Lumbar Spinal Cord Intrathecal Injection
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