Decreased dynorphin levels and increased kappa opioid receptor binding in male rats with isolation-induced hypertension.
The role of hippocampal dynorphin A (1-8) (Dyn A (1-8)) and kappa opioid receptors was investigated in the isolation-induced hypertensive rat (IHR). Male Sprague Dawley rats were either isolated (1 per cage) or grouped (3 per cage) for 7 days. Isolated rats exhibited increased blood pressure (systolic blood pressure 159.7 +/- 6.6 mmHg) whereas the grouped rats remained normotensive (systolic blood pressure 137 +/- 6.3 mmHg). Using radioligand binding techniques we observed a significant increase in kappa opioid receptor binding in the hippocampus of isolated rats (56% increase) and this further increased when the length of isolation was increased to 2 weeks (72% increase). Radioimmunoassay showed that isolation decreased the hippocampal content of Dyn A (1-8) from 12.7 +/- 0.4 to 11.6 +/- 0.2 pg Dyn A (1-8) per 10 mg tissue (rats weighing approximately 100 g) and from 13.3 +/- 0.8 to 9.7 +/- 1 pg Dyn A (1-8) per 10 mg tissue (approximately 200 g rats). These data suggest that functional alterations in the hippocampal dynorphin system may be involved in the maintenance of isolation induced hypertension.
Wright
R C
RC
Department of Pharmacology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
McConnaughey
M M
MM
Ingenito
A J
AJ
D000818:Animals; D004399:Dynorphins / Q000096:biosynthesis*; D006624:Hippocampus / Q000378:metabolism; D006976:Hypertension, Pulmonary / Q000188:drug therapy*; D008024:Ligands; D008297:Male; D011485:Protein Binding; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000096:biosynthesis*; D012934:Social Isolation; D013997:Time Factors
D008024:Ligands; D017473:Receptors, Opioid, kappa; D004399:Dynorphins