NONSELECTIVE ATTENTION AND NITRIC-OXIDE IN PUTATIVE ANIMAL-MODELS OF ATTENTION-DEFICIT HYPERACTIVITY DISORDER

Non-selective attention (NSA) to environmental stimuli has been measur ed in putative animal models of Attention-Deficit Hyperactivity Disord er (ADHD), such as the Spontaneously Hypertensive (SHR) and the Naples High-Excitability (NHE) rat lines. A series of experiments has been c arried out on male juvenile SHR and Wistar-Kyoto (WKY) controls (exper iment 1) and on the NHE and two controls, i.e. the Naples Low-Excitabi lity (NLE) and a random-bred (NRB) line (experiment 2). It was done un der basal conditions or following a single injection of the nitric oxi de synthase (NOS) inhibitor L-nitro-arginine-methylester (L-NAME; 0.1- 10 mg/kg, i.p.), or vehicle, 30 min before testing on day 1 and vehicl e alone before testing on days 2 and 3 in SHR/WKY (experiment 3) and t he Naples lines (experiment 4). The behavior in a Lat maze during thre e consecutive 10-min exposures at 24-h intervals was monitored by a CC D video camera and analyzed off-line for frequency and duration of rea rings on hindlimbs per 1-min blocks. The results demonstrated that bot h SHR and NHE rats showed a higher frequency of rearings of shorter du ration than controls. With time of testing, the duration of rearings t ended to increase in the WKY but not the SHR. In the Naples lines the duration tended to increase in all but mostly in the NHE rats. The acu te inhibition of NOS by L-NAME significantly increased the duration of rearing episodes both in SHR and NHE rats only at 10 mg/kg in the sec ond part of the testing period. Therefore, NSA, as indexed by the dura tion of rearings, is defective in both hyperactivity models against di fferent genetic backgrounds. In addition, this impairment is dependent upon nitric oxide (NO), which appears to play a significant role in t hese processes. (C) 1998 Elsevier Science B.V. All rights reserved.