The effect of criterion level on the acquisition and retention of a 1-way avoidance response in young and old rats.

Young (23-25 days old) and adult (80-84 days old) rats (n = 8, per group) were trained on an active-avoidance task to a criterion of 0, 5, or 15 consecutive correct trials and then tested for retention 30 days later. In original training, both age groups acquired the response in about the same number of trials when the criterion was set at 5/5 but young subjects required significantly more trials than older subjects to learn the response under the 15/15 criterion. In retraining, both age groups performed equally well when original training was to the 15/15 criterion although adults retained significantly better than weanlings when original training was 5/5 correct responses.

Adrenergic sulfonanilides. 4. Centrally active beta-adrenergic agonists.

The central nervous system (CNS) activities of a number of soterenol analogs have been investigated, and several of these compounds possessed potent morphine antagonistic and anorexiant properties. The CNS activity of these compounds was enhanced by certain lipophilic [e.g.

Aberrations of cyclic nucleotide metabolism in the hearts and vessels of hypertensive rats.

In the aortas and mesenteric arteries from spontaneous hypertensive rats and in the aortas from stress- and desoxycorticosterone-acetate-hypertensive rats, the intracellular cGMP: cAMP ratios were significantly elevated when compared to the ratios in the aortas of the respective controls. Decreases in the intracellular cAMP or cGMP levels were consistently associated with increased activity of the cyclic-nucleotide-specific low K(m) phosphodiesterase (3':5'-cAMP 5' nucleotidohydrolase, EC 3.1.