Opioid mechanisms involved in the slow potential change and neuronal refractoriness during cortical spreading depression

Abstract

The slow potential change (spc) accompanying spreading depression (SD) was studied in rats and in a seizure-sensitive strain of Mongolian gerbil under three different experimental paradigms, each involving the use of naloxone. Gerbils undergoing electroconvulsive shock treatment displayed SD during the post-ictal phase, which was blocked by the intraperitoneal (i.p.) administration of naloxone (20-50 mg kg-1). Topical application of naloxone to the exposed cortex of the anaesthetized gerbil and rat blocked the spc of SD evoked by KCl. Microiontophoretic ejection of naloxone during extracellular recordings reversed cell refractoriness following the spc, demonstrated by the observation of a maintained sensitivity to iontophoretic pulses of glutamate. The results suggest a possible involvement of naloxone-sensitive processes in the mechanism responsible for cortical SD.

Malnutrition and REM-sleep Deprivation Modulate in Rats the Impairment of Spreading Depression by a Single Sub-convulsing Dose of Pilocarpine

“…Their male pups formed, respectively, the M-and W-groups of this study. RBD has been largely used in our experimental studies on the effects of malnutrition (Silva et al, 1987;Guedes et al, 1987;Andrade et al, 1990;Teodosio et al, 1990;Rocha-De-Melo and Guedes, 1997;Pican(;o-Diniz et al, 1998). This experimental diet was prepared according to data from food consumption surveys in 918 families (5,939 persons) from the forested area of the south region of the Pernambuco State {for details, see Teodosio et al, 1990).…”

“…nutritional and pharmacological manipulations {Guedes, 1984;Guedes et al, 1987;1992;Santos-Monteiro d al., 2000;Costa-Cruz and Guedes, 2001). By using the pharmacological approach, we have previously demonstrated that adult epileptic rats in the chronic phase of the pilocarpine model of epilepsy (rats which had received a convulsing dose of that cholinergic muscarinic agonist 60-90 days before the experiment) presented a marked resistance to SD elicitation and propagation {Guedes and Cavalheiro, 1997).…”

Cortical spreading depression produces long-term disruption of activity-related changes in cerebral blood volume and neurovascular coupling

“…1 Clinically, CSD is postulated to play a role in the pathogenesis of stroke, 2 traumatic cortical injury, 3 cerebral ischemia, 4,5 migraine, 6 and transient global amnesia. 7 CSD can be induced by a variety of stimuli including pinprick or needle stab, 8,9 elevated potassium, 5,10 electrical stimulation, 1,11 or glutamate application. On a cellular level, electrophysiological changes are accompanied by significant shifts in intra-and extracellular ion concentrations, 12 cellular swelling, 13 dendritic beading, 14 and changes in gene expression.…”

Early malnutrition attenuates the impairing action of naloxone on spreading depression in young rats

“…19 In well-nourished animals, naloxone was shown to block CSD. 20,21 No information is available, however, on the possible action of early malnutrition in modulating the effects of naloxone on CSD.…”