Spinal nicotinic receptor activity in a genetic model of hypertension

Intrathecal cytisine, a nicotinic receptor agonist, elicits greater dose-de pendent increases in blood pressure, heart rate and nociceptive responses i n SHR than normotensive rat strains. Similar to adult rats, cardiovascular and nociceptive responses were augmented in prehypertensive SHR than age-ma tched WKY. While hydralazine or captopril pretreatment significantly lowere d blood pressure in both SHR and WKY rats, responses to i.t. cytisine were still greater in SHR. By contrast, i.t. cytisine elicited responses were no t exaggerated in DOCA-salt hypertensive WKY rats. Pressor and irritation re sponses to i.t. Cytisine can be divided into a transient, initial and persi sting, late phases. Both are augmented in SHR. In F1 rats, only the late ph ase pressor and pain responses to i.t. cytisine are similar in magnitude to those observed in SHR suggesting a possible dominant trait in the SHR. Ove rall, our findings suggest that hyper-responsiveness in nociception and pre ssor activity to spinal cytisine in SHR may be pathogenetically associated, but not a consequence, of hypertension.