Cardiovascular Effects of ?-Adrenoreceptor Blocking Agents After Intracerebroventricular Administration in Conscious Normotensive Cats

SUMMARY 1. Seven β-adrenoreceptor antagonists, namely (±)-propranolol, (—)-propranolol, (±)-alprenolol, pindolol (prindolol; LB46), practolol, ICI 66082, sotalol and oxprenolol, produced sustained falls in blood pressure and heart rate after intracerebroventricular (icv) administration in conscious, normotensive cats. 2. Transient initial rises in blood pressure and heart rate were observed after icv infusions of six of the β-adrenoreceptor antagonists used, the exception being ICI 66082. 3. The isomers (+)-propranolol and (+)-alprenolol, which are devoid of β-adrenoreceptor antagonist activity and the local anaesthetic agents procaine and lignocaine caused initial rises in blood pressure and heart rate, but did not subsequently cause any fall in either blood pressure or heart rate. 4. The time of maximum hypotension and bradycardia following icv administration of β-adrenoreceptor antagonists coincided with the maximum inhibition of the centrally mediated tachycardia in response to icv isoprenaline.