Investigating the influence of perinatal nicotine exposure on genetic profiles of neurons in the sub-regions of the VTA

Abstract

Chronic nicotine exposure during pregnancy has been shown to induce physiological and anatomical alterations in offspring. Previously, we investigated the complexity of dopamine (DA) neuron firing in the sub-regions of the ventral tegmental area (VTA) following perinatal nicotine exposure. Using approximate entropy, we found that within the middle sub-region, the parainterfascicular nucleus (PIF), there was higher complexity indicating more random neural firing and a less homogeneous neuron population. Therefore, we sought to investigate the neuron populations within the sub-regions of the VTA following perinatal nicotine exposure. We used real time PCR in order to find the relative quantity of glutamate to γ-aminobutyric acid (GABA), DA, and glutamate neurons within three sub-regions: the parabrachial pigmented nucleus (PBP), parainterfascicular nucleus (PIF), and paranigral nucleus (PN). Our results showed that the PIF region of the VTA contained a more diverse population of neurons resulting in a more complex system. In addition, we found that DA neurons are more activated in PN sub-region of the VTA, which mediates the rewarding effects of drugs including nicotine. Lastly, using immunohistochemistry, we observed an overall decrease in DA neurons following perinatal nicotine exposure.

Prenatal nicotine exposure alters gene expression profiles of neurons in the sub-regions of the VTA during early postnatal development

“…The main gene expression change happened in TH, DA neurons, in which we observed a consistently increased significance in PN sub-region compared to PIF and PBP at P7 PN vs PBP (p < 0.01), at P14 PN vs PIF (p < 0.05) and PN vs PBP (p < 0.05) and at P21 PN vs PIF (p < 0.05) and PN vs PBP (p < 0.05). This significance in expression of the DA neurons in the PN sub-region of the VTA in the P14 and P21 groups was consistent with our previous study of 28-day old rat pups, where there was a large increase of relative gene expression in DA neurons in the PN sub-region of the VTA compared to the saline group 12 . We also observed that GABA and glutamate neurons were also developing in the sub-regions of the VTA and dominated different regions of the VTA, acting complementary to the development of the DA neurons.…”

“…Interactions with addictive drugs have shown behaviors of aggression, compulsion, and lack of social play because of the mesocorticolimbic DA circuitry with the NAc and PFC 11 . Previously, our lab published a study that observed the three sub-regions of the VTA in rats following gestational exposure to nicotine at 28 days after birth 12 . Samples were collected from 28-day old rat pups following exposure to nicotine prenatally as well as through breast milk after birth 12 .…”

“…Previously, our lab published a study that observed the three sub-regions of the VTA in rats following gestational exposure to nicotine at 28 days after birth 12 . Samples were collected from 28-day old rat pups following exposure to nicotine prenatally as well as through breast milk after birth 12 . Gene expression from these three sub-regions sought to show the expression of GABA (GAD1, also known as GAD67, and GAD2, also known as GAD65), DA (Slc6a3, TH), and glutamate (Slc17a6) neuron markers when nicotine-exposed pups were compared with saline exposed pups 12 .…”

“…Samples were collected from 28-day old rat pups following exposure to nicotine prenatally as well as through breast milk after birth 12 . Gene expression from these three sub-regions sought to show the expression of GABA (GAD1, also known as GAD67, and GAD2, also known as GAD65), DA (Slc6a3, TH), and glutamate (Slc17a6) neuron markers when nicotine-exposed pups were compared with saline exposed pups 12 . It was most notable that DA neurons are more activated in the PN sub-region of the VTA.…”

Investigating the influence of perinatal nicotine and alcohol exposure on the genetic profiles of dopaminergic neurons in the VTA using miRNA–mRNA analysis

“…Glutamate pathways are linked to many other neurotransmitter pathways as glutamate receptors are found throughout the brain and spinal cord in neurons and glia 76 . A subset of DA neurons in the VTA co-release DA and glutamate to the NAc and are believed to play a role in behavioral activation following stimulants, illustrating a role in drug addiction 77 – 79 . This could partly explain the enriched glutamatergic synapse pathway as alcohol directly activates the DA, playing an essential role in neurodevelopment 80 .…”