Inhibition of stress-induced hyperglycemia by tail pinching or intraventricular enkephalin administration in the rat.
The tail pinch (t-p) method added to a basal restraint stress produced inhibition of the stress-induced hyperglycemia, an effect that was neutralized with intrathecal anesthesia but not with intracerebroventricular (i.c.v.) naloxone (50, 100, 1000 ng/100 g) or with intraperitoneal naloxone injections (0.1-0.3 mg/100 g). A similar negative result was obtained with i.c.v. administration of 500 and 1000 ng/100 g of beta-endorphin. In contrast, a single i.c.v. injection of 1000 ng/100 g of Met-enkephalin reproduced the t-p inhibitory effect. The latter was not elicited by i.c.v. FK 33824, an enkephalin analogue, a result that supports the specific participation of the delta-opioid receptors. The results obtained with central alpha-adrenoceptor antagonists and central noradrenergic chemical destruction, or central alpha-adrenoceptor agonists, support the production of a reinforcement of the alpha-adrenoceptor stress stimulation by the t-p procedure, probably through noradrenaline and enkephalin mediation.
D000818:Animals; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D006943:Hyperglycemia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D007276:Injections, Intraventricular; D007328:Insulin / Q000097:blood; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012149:Restraint, Physical; D013623:Tail / Q000294:innervation* / Q000503:physiopathology
D007328:Insulin; D009270:Naloxone; D004744:Enkephalin, Methionine; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin