4Sought to replicate and extend the findings of the 2nd author and W. W. Beatty (see record 1981-29710-001) that lesions of the dorsomedial thalamus (DMT) or the parafascicular area of the thalamus (PFA) reduced the frequency of pinning, believed to be a valid indicator of juvenile play in the rat. Data from 54 juvenile Long-Evans rats indicate that lesions of either the DMT or the PFA reduced rough-and-tumble social play, as measured by the frequency of pinning. Pinning was reduced by 33% in Ss with DMT lesions and by 73% in Ss with PFA lesions. Although PFA lesions had minimal effects on average pin durations, DMT-lesioned Ss had pins that were, on the average, 105% longer than those of controls. Lesions of the PFA also reduced play solicitation behaviors. Ss with PFA lesions were also insensitive to the play modulating effects of both naloxone HCl (1 mg/kg) and morphine sulfate (1 mg/kg). DMT-lesioned Ss were sensitive to the facilitatory effects of morphine, but naloxone was without effect in these Ss. Control studies designed to evaluate general behavioral competence showed that the observed lesion effects were relatively specific to play. (44 ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)
