Facilitation of Recovery after Lateral Hypothalamic Damage by Prior Ablation of Frontal Cortex

BILATERAL lesions of the lateral hypothalmus in the rat produce aphagia and adipsia¹, but if the animals are kept alive by intragastric feeding they may begin to eat and drink spontaneously again after a few days^1–4. It has been suggested⁵ that recovery of feeding depends on the recovery of an adrenergic reward system, partial denervation of which may account for less severe deficits in feeding behaviour after other lesions of the central nervous system. For example, ablation of frontal cortex in the rat results in progressive loss of weight for 3–4 days, followed by recovery⁶ and also in changed sensitivities to drugs affecting noradrenergic synapses^7,8. It seems possible that denervation supersensitivity may be the explanation of the recovery of function^8,9. We suggest that lateral hypothalamic lesions may partially denervate hypothalamic neurones as a result of the destruction of intrahypothalamic connexions. Thus if lateral hypothalamic neurones were partially denervated by ablation of frontal cortex at some time before damage to the lateral hypothalamus itself, delayed supersensitivity from the cortical lesion should result in facilitated recovery. We now present data to support this hypothesis.     

Ecological cues, gestation length, and birth timing in African buffalo (Syncerus caffer)

We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year.