Asymmetry of reinforcing properties of the lateral hypothalamus in the self-stimulation test

In the protocols of modern pharmacological studies of a self-stimulation reaction in rodents, stimulating electrodes are implanted as a rule unilaterally. The reinforcing properties of the left and right hypothalamus were suggested to be identical. The aim of the study was to clear up if the possibilities of the left and right hypothalamus to produce self-stimulation are similar or not. Methods. The study was carried out on adult male Wistar rats. The electrodes were implanted into the lateral hypothalamus bilaterally. The rats, in which an approach reaction was observed, learned self-stimulation in the Skinner box with stimulation of the left or right hypothalamus as a reinforcing agent descending thresholds of stimulation up to minimal one. Results. Self-stimulation of the left hypothalamus gave an approach reaction in the majority of rats (81.8%), self-stimulation reaction was developed in 72.7% of rats. Only 46.2% rats reacted on stimulation of the right hypothalamus, self-stimulation reaction was developed in 30.8% of rats. The thresholds of positive and negative reactions registered after electrical stimulation of both sides of hypothalamus were significantly differed (H(3, N = 31) = 14,92; p = 0,002). And these changes were not connected with lateralization but with sign of reaction: in general the thresholds of approach reaction were higher than thresholds of avoidance. Conclusion. In the paper, the fact of different possibility of approach reaction and self-stimulation development as a result of electrical stimulation of the left and right hypothalamus in rats has been described. After stimulation of the left hypothalamus, a possibility to receive positive reaction and to form self-stimulation on its basis is higher than after stimulation of the right hypothalamus. (For citation: Efimov NS, Bessolova YN, Karpova IV, et al. Asymmetry of reinforcing properties of the lateral hypothalamus in the self-stimulation test. Reviews on Clinical Pharmacology and Drug Therapy. 2018;16(2):37-41. doi: 10.17816/RCF16237-41).