Trigeminal deafferentation and ingestive behavior in rats.

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Abstract
For studying the role of orosensory input in the control of ingestive behavior, rats were subjected to varying degrees of trigeminal deafferentation. Somatosensory branches that convey touch, temperature and pain from the oral cavity were sectioned selectively and innervation of the muscles of mastication and taste afferents were left intact. Severe intake deficits were produced, which included aphagia, adipsia and prolonged hypophagia accompanied by a corresponding decrease in body weight. The deficits were proportional to the extent of deafferentiation and were most severe when upper and lower portions of the mouth were affected. Although somatosensory impairment affected the organization of the consummatory response, all rats could bite, chew and lick. Analysis of feeding patterns of minimally (mandibular) deafferented rats showed that the animals compensated for the consummatory inefficiency by increasing meal duration but failed to initiate meals at the normal rate, thus keeping food intake below normal levels. Oral somatosensory input is apparently critical for the mechanisms that regulate ingestive behavior.