Role of Dopamine Type 1 Receptors and Dopamine- and cAMP-Regulated Phosphoprotein Mr 32 kDa in Δ⁹-Tetrahydrocannabinol–Mediated Induction of ΔFosB in the Mouse Forebrain

Abstract

D 9 -Tetrahydrocannabinol (THC), the main psychoactive component of marijuana, produces motor and motivational effects via interactions with the dopaminergic system in the caudateputamen and nucleus accumbens. However, the molecular events that underlie these interactions after THC treatment are not well understood. Our study shows that pretreatment with dopamine D 1 receptor (D 1 R) antagonists before repeated administration of THC attenuated induction of D FBJ murine osteosarcoma viral oncogene homolog B (DFosB) in the nucleus accumbens, caudate-putamen, amygdala, and prefrontal cortex. Anatomical studies showed that repeated THC administration induced DFosB in D 1 R-containing striatal neurons. Dopamine signaling in the striatum involves phosphorylation-specific effects of the dopamine-and cAMP-regulated phosphoprotein Mr 32 kDa (DARPP-32), which regulates protein kinase A signaling. Genetic deletion of DARPP-32 attenuated DFosB expression measured after acute, but not repeated, THC administration in both the caudate-putamen and nucleus accumbens. THC was then acutely or repeatedly administered to wild-type (WT) and DARPP-32 knockout (KO) mice, and in vivo responses were measured. DARPP-32 KO mice exhibited enhanced acute THC-mediated hypolocomotion and developed greater tolerance to this response relative to the WT mice. Agonist-stimulated guanosine 59-O-(3- These results indicate that D 1 Rs play a major role in THC-mediated DFosB induction in the forebrain, whereas the role of DARPP-32 in THC-mediated DFosB induction and modulation of motor activity appears to be more complex.

Δ9-Tetrahydrocannabinol Experience Influences ΔFosB and Downstream Gene Expression in Prefrontal Cortex

“…First, a history of repeated THC treatment enhanced acute THC-mediated increases in ΔFosB mRNA in PFC and NAc. We previously reported that repeated THC treatment induced ΔFosB protein in PFC, NAc, CPu, and amygdala 20 , 23 as replicated here, and prior studies showed that repeated treatment with psychostimulants 24 or morphine 25 induced ΔFosB in these same regions. Second, induction of ΔFosB by repeated THC treatment was associated with increased expression of Cdk5 and p35 only in PFC.…”

“… 15 , 30 The reason that Cdk5 is induced in different regions by THC versus cocaine is not known. ΔFosB induction by both THC and psychostimulants requires D 1 R activation, 20 , 24 suggesting a common upstream site of action. Both drug classes induce ΔFosB in D 1 R/dynorphin-expressing medium spiny neurons (MSNs) in the NAc.…”

“… 13 , 19 PFC, NAc, caudate-putamen (CPu), and amygdala (Amyg) were dissected as published. 9 , 20 Experiments were approved by VCU IACUC in accordance with the NIH Guide for Care and Use of Laboratory Animals.…”

“…Immunoblotting was performed as published. 20 Tissue was homogenized and loaded in 10% or 12% (Cdk5, p35, and p25) Tris-HCl gels and separated by electrophoresis. Gels were transferred onto nitrocellulose paper, blocked, and incubated in antibody in 0.1 M Tris-buffered saline (0.9%; pH 7.4; TBS) containing 0.1% Tween-20 (TBST) with 5% nonfat dry milk or 5% bovine serum albumin (for phosphorylated proteins).…”

Central HIV-1 Tat exposure elevates anxiety and fear conditioned responses of male mice concurrent with altered mu-opioid receptor-mediated G-protein activation and β-arrestin 2 activity in the forebrain

“…Each brain region was dissected as we have described (Lazenka et al, 2014; Lazenka et al, 2015), flash frozen and stored at −80 °C. On the day of each assay, samples were thawed, homogenized in ice-cold membrane buffer (50 mM Tris–HCl, pH 7.4, 3 mM MgCl 2 , 1 mM EGTA and 100 mM NaCl) and centrifuged at 48,000 × g at 4 °C for 10 min.…”