Ketanserin

25CN-NBOH (a kind gift from Jesper L. Kristensen, University of Copenhagen) and ketanserin (Tocris Biosciences; Avonmouth, UK) were dissolved in isotonic saline, SB-242084 (Tocris Biosciences; Avonmouth, UK) in DMSO (10% in saline). Drugs were applied intraperitoneally or subcutaneously (<10 ml/kg), as indicated.

The selective 5‐HT_2A agonist TCB‐2 and 5‐HT_2A/2C antagonist ketanserin were purchased from Tocris Biosciences (Bristol, UK). To elucidate the effects of 5‐HT_2A activation on intrinsic neuronal properties irrespective of network activity, the GABA_A antagonists bicuculline methiodide (Enzo Life Sciences, Farmingdale, NY) and gabazine (Tocris, Bristol, UK) and the AMPA antagonist 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX) (Alomone Labs, Jerusalem, Israel) were used either alone or together in most experiments. Bicuculline, gabazine, and TCB‐2 were each diluted into aliquots of 10 mmol/L stocks, DNQX was diluted to 20 mmol/L, and ketanserin was stored in 1.25 mmol/L aliquots. All drugs were stored at −80°C and then diluted to working concentrations of 10 μmol/L TCB‐2, 10 μmol/L bicuculline, 10 μmol/L gabazine, 20 μmol/L DNQX, and 750 nmol/L ketanserin in aCSF. Any drugs that were not used within 3 days of thawing were discarded. For electrophysiology experiments, brain slices were superfused with drug solutions for 5 min prior to any data acquisition.

To test the contribution of the serotonergic system on pups’ neural activity associated with maternal presence, pharmacological modifications were performed using drugs injected intraperitoneally.
To block serotonergic signaling, we targeted 5-HT2R using the 5-HT_2A/2CR antagonist ketanserin (2.5 mg/kg; Tocris, catalog #0908; Sarkar et al., 2014 (link)). ketanserin is a strong 5-HT2AR and 5-HT2CR antagonist with weak associated α‐adrenergic blocking and anti-histamine activity (Awouters, 1985 (link)). To enhance serotonergic signaling, we used the SSRI fluoxetine (10 mg/kg; Sigma, catalog #1279804; Ansorge et al., 2004 (link)). These drugs and vehicle (0.9% saline) were injected at a volume of 0.02 ml per 10 g. fluoxetine does not readily dissolve in saline solution so fluoxetine was first diluted in sterile water and then NaCl was added. Average pup weight was 25.46 ± 4.7 g. To ensure that the experimenter was blind to the treatment of the animals, the solutions were prepared by a different experimenter and color coded. The color code was only revealed after histologic and data analyses.