Abstract
The present experiments, part of an ongoing study designed to characterise the role norepinephrine (NE) in regulating the activity of putative nociceptive modulatory neurons in the rostral ventromedial medulla (RVM), assessed the effects of α-adrenergic receptor-selective agents on the nociceptive threshold (as measured by the tail-flick withdrawal response on noxious heat). These microinjection studies were carried out in the barbiturate-anesthetized rat, a preparation which is favourable for acute neurophysiological studies. The data obtained demonstrate that, as observed by others in the awake animal, activation of α2-adrenergic receptors in the RVM produces hypoalgesia. However, unlike in the awake animal, when antagonists selective for either the α1- or α2-adrenergic receptor are microinjected alone into the RVM there is no change in the nociceptive threshold. These data suggest that the α2-adrenergic receptor has a postsynaptic location and that barbiturate anaesthesia suppresses a tonically active or noxious stimulus-activated noradrenergic input to the RVM that is present in the awake animal.
Original language | English (US) |
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Pages (from-to) | 192-195 |
Number of pages | 4 |
Journal | Brain research |
Volume | 533 |
Issue number | 2 |
DOIs | |
State | Published - Nov 19 1990 |
Externally published | Yes |
Keywords
- Antinociception
- Brainstem
- Microinjection
- Noradrenaline
- Rat
ASJC Scopus subject areas
- General Neuroscience
- Molecular Biology
- Clinical Neurology
- Developmental Biology