Ibotenic acid lesion of the lateral hypothalamus increases preference and aversion thresholds for saccharin and alters the morphine modulation of taste.
In a previous study we showed that bilateral ibotenic acid lesions of the lateral hypothalamus in rats induced an increase in gustatory preference thresholds for saccharin solutions and which were associated with body weight and daily water intake impairments. The first aim of the present study was an attempt to dissociate the body weight and water intake deficits from the increase in gustatory thresholds. For this purpose we compared the effect of simultaneous bilateral lesions of the lateral hypothalamus with the effect of successive lesions in which each unilateral destruction was separated by a 10-day interval. Rats injected with vehicle only (either simultaneously or successively) served as controls. The two types of lesion produced very similar deficits, namely permanent body weight and water intake decreases, as well as a shift to the right in gustatory preference-aversion functions for saccharin (two-bottle procedure). The second aim of the present study was to analyse the effect of morphine (2 mg/kg SC) on saccharin preference in both lesioned and control rats. It was observed that for moderate and high concentrations of the sweetener morphine increased preference for saccharin over water but this effect was similar in both groups of rats. However, with a low concentration of the sweetener (0.3 mM) morphine clearly induced an opposite effect in the two groups of rats: the significant preference for this concentration shown by the control rats after vehicle injection was converted to a neutral response, whereas the neutral response of the lesioned animals after vehicle injection was transformed by morphine to a significant preference for saccharin over water.(ABSTRACT TRUNCATED AT 250 WORDS)
Touzani
K
K
Laboratoire de Psychophysiologie, URA CNRS 339, Université de Bordeaux I, Talence, France.
Velley
L
L
D000818:Animals; D005518:Food Preferences / Q000187:drug effects*; D007026:Hypothalamic Area, Lateral / Q000187:drug effects / Q000502:physiology*; D007051:Ibotenic Acid / Q000633:toxicity*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010080:Oxazoles / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains; D012439:Saccharin; D012684:Sensory Thresholds / Q000187:drug effects; D013649:Taste / Q000187:drug effects* / Q000502:physiology
D010080:Oxazoles; D007051:Ibotenic Acid; D009020:Morphine; D012439:Saccharin