Basal forebrain knife cuts and medial forebrain bundle self-stimulation.
Current autoradiographic and electrophysiological data suggest that fibers coursing from the diagonal band/medial septum and lateral preoptic area through the medial forebrain bundle (MFB) to the midbrain may carry the reward signals generated by lateral hypothalamic stimulation. To test this hypothesis, 40 rats were given a unilateral lateral hypothalamic stimulating electrode and an ipsilateral guide cannula for knife cut transection. In baseline self-stimulation testing, both the animal's capacity to respond for the stimulation and the reward efficacy of the stimulation were measured. A coronal plane knife cut transection was given following stabilization of baseline behavior, and any changes in response capacity and stimulation reward efficacy were observed for up to two weeks, beginning 24 h after transection. Cuts to the diagonal band/medial septal region or the outflow therefrom did not permanently or significantly alter stimulation reward effectiveness. Cuts in the lateral preoptic area or in the MFB just anterior to the stimulating electrode decreased stimulation reward effects only if considerable concomitant rostrocaudal tissue damage was apparent around the knife cut. Even in these cases, reward degradation was rarely permanent. These results suggest that the majority of reward-relevant fibers probably do not arise in forebrain nuclei rostral to the stimulating electrode. A possible role of neurons endemic to the lateral hypothalamus in stimulation reward effects is discussed.
Waraczynski
M A
MA
Department of Psychology, Harvard University, Cambridge, MA 02138.
D000818:Animals; D001931:Brain Mapping; D004558:Electric Stimulation; D005625:Frontal Lobe / Q000502:physiology*; D007026:Hypothalamic Area, Lateral / Q000502:physiology; D008297:Male; D008474:Medial Forebrain Bundle / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D011301:Preoptic Area / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time; D012653:Self Stimulation / Q000502:physiology*