Innervation of the medial prefrontal cortex by tyrosine hydroxylase immunoreactive fibers during adolescence in male and female rats

Abstract

Adolescence is associated with continued maturation of the cerebral cortex, particularly the medial prefrontal cortex (mPFC). We have previously documented pruning in the number of neurons, dendrites and synapses in the rat mPFC from preadolescence to adulthood, with the period of pubertal onset being particularly important. We hypothesized that dopaminergic innervation of this region, critical for executive functions, would also be influenced by pubertal onset. Here, we measured changes in the volume of tyrosine hydroxylase (TH) immunoreactive axons in all layers of the male and female mPFC from preadolescence to adulthood (postnatal day (P) 25, 35, 45, 60 and 90) as a marker of dopaminergic innervation. Assessing both total fiber volume and length, TH fibers were quantified by multiplying the mPFC volume by fiber density. While there were subtle layer-specific changes, TH fiber volume and length increased between P25 and P90 in both males and females. Contrary to our hypothesis, a role for pubertal onset in TH innervation of this region was not discernable. In summary, axons immunoreactive for TH increase with similar trajectories in the mPFC of male and female rats from pre-puberty to young adulthood.

Adolescence and “Late Blooming” Synapses of the Prefrontal Cortex

“…Histological studies have also shown striking late growth of dopaminergic terminals into the primate and rodent PFC extending from the juvenile period well into the young adult period (Kalsbeek et al 1988;Benes et al 2000;Naneix et al 2012;Willing et al 2017;Hoops et al 2018). In mice, dopaminergic boutons in the PFC show greater activity-dependent plasticity in mid adolescence compared to adulthood (Mastwal et al 2014).…”

Role of Spinal Cord α2-Adrenoreceptors in Noradrenergic Inhibition of Nociceptive Transmission During Chemotherapy-Induced Peripheral Neuropathy

“…The total DBH fibers length in each lamina of spinal dorsal horn were also calculated using a semi quantitative skeleton analysis adapted from Willing et al (2017). Briefly, after an adjustment of the threshold level as abovementioned, the images were converted to binary images, skeletonized using the skeleton macro from ImageJ and evaluated in terms of number of pixels occupied by skeletons.…”

Cortical reorganization during adolescence: What the rat can tell us about the cellular basis

“…7 The total volume of the tyrosine hydroxylase containing axons in the rat mPFC in males (a) and female (b). *p < .05 ( Willing et al, 2017 ). …”

“…We quantified the growth of axons carrying tyrosine hydroxylase (the rate limiting step for dopamine synthesis) across adolescence with regard to both sexes and puberty. A definitive role for puberty was not apparent ( Willing et al, 2017 ) ( Fig. 7 ).…”