ABSTRACT
Neuronal cannabinoid receptors (CB(1)) are coupled to inhibition of voltage-sensitive Ca(2+) channels (VSCCs) in several cell types. The purpose of these studies was to characterize the interaction between endogenous CB(1) receptors and VSCCs in cerebellar granule neurons (CGN). Ca(2+) transients were evoked by KCl-induced depolarization and imaged using fura-2. The CB(1) receptor agonists CP55940, Win 55212-2 and N-arachidonylethanolamine (anandamide) produced concentration-related decreases in peak amplitude of the Ca(2+) response and total Ca(2+) influx. Pre-treatment of CGN with pertussis toxin abolished agonist-mediated inhibition. The inhibitory effect of Win 55212-2 on Ca(2+) influx was additive with inhibition produced by omega-agatoxin IVA and nifedipine but not with omega-conotoxin GVIA, indicating that N-type VSCCs are the primary effector. Paradoxically, the CB(1) receptor antagonist, SR141716, also inhibited KCl-induced Ca(2+) influx into CGN in a concentration-related manner. SR141716 inhibition was pertussis toxin-insensitive and was not additive with the inhibition produced by Win 55212-2. Confocal imaging of CGN in primary culture demonstrate a high density of CB(1) receptor expression on CGN plasma membranes, including the neuritic processes. These data demonstrate that the CB(1) receptor is highly expressed by CGN and agonists serve as potent and efficacious inhibitory modulators of Ca(2+) influx through N-type VSCC.
Subject(s)
Calcium/metabolism , Cerebellum/physiology , Neurons/physiology , Receptors, Drug/agonists , Animals , Arachidonic Acids/pharmacology , Benzoxazines , Calcium Channel Blockers/pharmacology , Calcium Channels/physiology , Cells, Cultured , Cerebellum/cytology , Cerebellum/metabolism , Electrophysiology , Endocannabinoids , Female , Male , Morpholines/pharmacology , Naphthalenes/pharmacology , Neurons/metabolism , Polyunsaturated Alkamides , Rats , Receptors, Cannabinoid , Receptors, Drug/antagonists & inhibitors , Receptors, Drug/physiologyABSTRACT
Flavin-containing monooxygenases (FMOs) catalyze the oxidation of a diverse array of xenobiotic compounds. The purpose of this investigation was to develop a specific immunological probe to human hepatic flavin-containing monooxygenase (HLFMO3). An oligopetide corresponding to amino acid residues 257-270 of HLFMO3 was coupled to keyhole limpet hemocyanin (KLH) through the sulfhydryl group of a cysteine residue added to the amino-terminus of the peptide. This peptide-KLH conjugate was used to generate a polyclonal antibody. The resulting immunoglobulin showed specific Western blot reactivity with HLFMO3 protein in human hepatic microsomes, the same protein that is recognized by a polyclonal antibody directed against macaque liver FMO. These findings demonstrate that an antibody directed against a synthetic peptide derived from HLFMO3 can be easily produced in large quantities and used in studies for the immunodetection and immunoquantification of HLFMO3. This is also the first antipeptide antibody directed against an FMO of any species.
