PACAP modulates rat sympathetic neuron depolarization through IP3

Origins and neurochemical complexity of preganglionic neurons supplying the superior cervical ganglion in the domestic pig

The superior cervical ganglion (SCG) is a center of sympathetic innervation of all head and neck organs. SCG sympathetic preganglionic neurons (SPN) were found in the nucleus intermediolateralis pars principalis (IMLpp), the nucleus intermediolateralis pars funicularis (IMLpf), the nucleus intercalatus spinalis (IC), and the nucleus intercalatus spinalis pars paraependymalis (ICpe). Despite its importance, little is known of SCG innervation and chemical coding in the laboratory pig, a model that is physiologically and anatomically representative of humans. Here in our study, we established the distribution and chemical coding of Fast Blue (FB) retrogradely labelled SPN innervating porcine SCG. After unilateral injection of FB retrograde tracer into the left SCG, labeled neurons were found solely on the ipsilateral side with approximately 98 % located in Th₁–Th₃ segments and predominantly distributed in the IMLpp and IMLpf. Neurochemical analysis revealed that approximately 80 % of SPN were positive both to choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) and were surrounded by a plethora of opioidergic and peptiergic nerve terminals. The results of our study provide a detailed description of the porcine preganglionic neuroarchitecture of neurons controlling the SCG, setting the stage for further studies concerning SPN plasticity under experimental/pathological conditions.

Knocked down and out: PACAP in development, reproduction and feeding

One approach to understanding the role of PACAP in vivo is to knockdown the translation of PACAP mRNA to protein or to knock out the PACAP gene by targeted disruption. In this paper, we review the effect of PACAP knockdown with morpholinos on early brain development in zebrafish. Also reviewed is the role of PACAP at several stages of reproduction as assessed in mice with a disrupted PACAP gene. New data are presented to analyze PACAP's action in energy homeostasis (body mass, food intake, endocrine parameters) using female PACAP-null mice. The evidence suggests PACAP is important for brain development in zebrafish and is required for normal reproduction, but not for body mass or food intake in mice maintained near thermoneutrality.

Pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide inhibit dendritic growth in cultured sympathetic neurons

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are related neuropeptides that are released by the preganglionic sympathetic axons. These peptides have previously been implicated in the regulation of sympathetic neurotransmitter metabolism and cell survival in postganglionic sympathetic neurons. In this study we consider the possibility that PACAP and VIP also affect the morphological development of these neurons. Postganglionic rat sympathetic neurons formed extensive dendritic arbors after exposure to bone morphogenetic protein-7 (BMP-7) in vitro. PACAP and VIP reduced BMP-7-induced dendritic growth by approximately 70-90%, and this suppression was maintained for 3 weeks. However, neither PACAP nor VIP affected axonal growth or cell survival. The actions of PACAP and VIP appear to be mediated by PAC1 receptors because their effects were suppressed by an antagonist that binds to PAC1 and VPAC2 receptors (PACAP6-38), but not by an antagonist that binds to the VPAC1 and VPAC2 receptors. Moreover, exposure to PACAP and VIP caused phosphorylation and nuclear translocation of cAMP response element-binding protein, and agents that increase the intracellular concentration of cAMP mimicked the PACAP-induced inhibition of dendritic growth. These data suggest that peptides released by preganglionic nerves modulate dendritic growth in sympathetic neurons by a cAMP-dependent mechanism.