Characterization of signal transduction pathways of alpha-1 adrenergic receptors in neonatal ventral hippocampus lesion rat model

Neonatal ventral hippocampus (nVH) lesioned animals show molecular and behavioral abnormalities analogous to those described in schizophrenia. As an extension to previous studies that showed an increase in ligand binding of cortical alpha-1 adrenergic receptors (AR) and a dysfunction in alpha-1 AR regulation of mesolimbic dopamine functions in post-pubertal nVH lesioned rats, we investigated the subcellular expression and activity of protein kinase C (PKC)---a second messenger in alpha-1 AR signaling---in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of post-pubertal nVH lesioned rats. Western blot analysis of membrane and cytosolic fractions showed complex changes in lesioned animals in the expression of different PKC subtypes following saline or alpha-1 AR agonist (cirazoline i.p.) injection. Among these changes, nVH lesioned animals showed a significant increase in membrane bound PKC alpha and phospho-PKC, and a decrease in cytosolic PKC gamma and PKC betaII in the PFC in comparison to sham-lesioned controls following saline. Cirazoline increased membrane bound PKC alpha in controls but decreased it in lesioned animals. In the NAcc, lesioned animals showed an increase in membrane bound and cytosolic PKC epsilon and PKC lambda levels following saline. Following cirazoline, lesioned animals showed a decrease in membrane bound PKC epsilon and PKC lambda, while controls showed an increase in cytosolic and membrane fractions of PKC epsilon with no change in PKC lambda. In vitro PKC activity assays showed increased basal activity in PFC slices of lesioned animals compared to controls, with no difference in NAcc slices. alpha-1 AR stimulation by the agonist phenylephrine (PE) increased PKC activity in PFC of controls while decreasing activity substantially in lesioned animals. In the NAcc, high concentrations of PE increased activity in controls, but decreased activity in lesioned animals. This abnormal expression and activity of PKC in the PFC and NAcc of nVH lesioned animals may be related to abnormal alpha-1 AR functions and may modulate some of the abnormal neuronal functions in these animals, such as working memory deficits and hyper neuronal excitability of the PFC and the NAcc