Noradrenergic stimulation of the lateral hypothalamus as a reinforcement in T maze learning in rats.

Since the time when Olds and Milner (15) have discovered that electrical stimulation of certain brain areas can serve as a reinforcement for motivated behavior, it has been shown that electrical stimulation of certain areas within the lateral hypothalamus evoked both self-stimulation and eating responses (14). These data became the basis for the view that drive induction rather than drive reduction constitutes the reinforcement of motivated behavior. Besides electrical stimulation the alimentary drive can also be induced by noradrenergic stimulation of certain loci w i t h the hypothalamus (3, 4, 8-12, 20). If drive induction does have reinforcing properties for motivated behavior, this noradrener-gic stimulation should have reinforcing properties as well. The aim of our paper was to verify this assumption. The experiment was carried out on 5 male hooded rats weighing 250-300 g. The animals were permanently implanted with bilateral cannulas aimed at the perifornical region of the anterior part of the lateral hypothalamus (LH). Chronic cannulas were implanted stereo-taxically under Nembutal anesthesia, according to the procedure described in detail by Slangen and Miller (20) with the use of the following coordinates: 0.0 mm (bregma) anterior, 1.3 mm lateral and 8.2 rnrn vertical with the teeth bar 3.1 mm above the intra-aural line. This part of the brain is known to elicit a reliable eating response to noradrenergic stimulation (20) in sated rats. Noradrenaline (NA) was