The Increased Sex Differences in Susceptibility to Emotional Stimuli during Adolescence: An Event-Related Potential Study.

The present study investigated how pubertal development and sex interact to influence humans' emotion susceptibility during adolescence. Event-related potentials were recorded for highly emotional, mildly emotional and neutral stimuli in positive and negative blocks, when 73 adolescents (36 pre-/early pubertal students, 19 boys, 10-12 years old; 37 mid-/late pubertal students, 18 boys, 11-13 years old) performed an implicit emotion task. Behavioral analysis showed higher positive mood ratings for pre-/early compared to mid-/late pubertal subjects, irrespective of sex and block. ERP analysis demonstrated increasing Late Positive Potential (LPP) amplitudes from neutral, Mildly Positive (MP) to Highly Positive (HP) stimuli in pre-/early pubertal, but not in mid-/late pubertal adolescents. However, girls exhibited higher P3a amplitudes during mid-/late relative to pre-/early puberty for negative stimuli irrespective of intensity; while this puberty effect was absent in boys. In addition, girls compared to boys exhibited a more pronounced LPP enhancement effect for Highly Negative (HN) stimuli and a lower threshold of responding to negative stimuli in P3b amplitudes, regardless of puberty. These results suggest that, though there is a puberty-independent sensitivity to negative stimuli in girls relative to boys, puberty selectively intensifies girls' attention bias for negative stimuli and reduces experiential sensitivity to positive stimuli in both sexes. The implication of these results for the sex-related psychopathology during adolescence were discussed.

Repeated administration of 5-hydroxytryptamine 2C agonist MK212 produces a sensitization effect of antipsychotic activity.

5-Hydroxytryptamine 2C (5-HT2C ) receptor agonists have been suggested to possess an antipsychotic activity in several acute preclinical tests of antipsychotic drugs with low extra-pyramidal side effect liability. However, little is known about the long-term effect associated with chronic use of 5-HT2C receptor agonists. The present study examined whether repeated activation of 5-HT2C receptor with a highly selective 5-HT2C receptor agonist MK212 would induce a long-term change in its antipsychotic-like activity (either a sensitization or tolerance) in the conditioned avoidance response and MK801-induced hyperlocomotion tests. Sprague-Dawley rats were first tested under the intraperitoneal (i.p.) treatment of MK212 (0.25, 0.5, 1.0 mg/kg) for 5 consecutive days. Three days later, when all rats were injected with a low dose of MK 212 (0.25 mg/kg) and tested for avoidance responding, rats that had been pretreated with 1.0 and 0.5 mg/kg MK212 made significantly fewer avoidance responses than those that had been treated with vehicle (0.9% saline). However, this past drug exposure-induced group difference was not significant in the MK801-induced hyperlocomotion test. Overall, results from this study suggest that repeated treatment of MK212 is capable of inducing a dose-dependent sensitization of antipsychotic activity in conditioned avoidance response. The discrepancy in sensitization of MK212 in CAR and MK801-induce hyperlocomotion may be related to the different mechanism underlying the effect of MK212 in these two tests. © 2016 IUBMB Life, 68(12):985-993, 2016.