Chronic iminodipropionitrile (IDPN) causes no changes in the rat brain phencyclidine (PCP) receptor

The iminodipropionitrile (IDPN)-induced dyskinetic syndrome: behavioral and biochemical pharmacology

Chronic administration of iminodipropionitrile causes a persistent behavioral syndrome which is characterized by lateral and vertical head shakes, random circling, hyperactivity and increased acoustic startle response in rodents. These behavioral abnormalities are similar to those observed after the acute administration of serotonin (5-HT) and dopamine (DA) agonists, and of some peptides including thyrotropin-releasing hormone (TRH) and the enkephalins. The data available so far indicate that the 5-HT system which interacts with some other neurotransmitters such as DA and norepinephrine (NE) in both reciprocal and nonreciprocal ways may be primarily involved in the manifestations of this persistent dyskinetic syndrome. Preliminary evaluation of the peptidergic systems has also revealed possible involvement of opiate peptides in the IDPN-induced dyskinetic phenomena. More studies are needed to assess the role of specific molecular events which may occur at cortical, subcortical, and/or spinal levels to cause this interesting psychomotor syndrome.

The iminodipropionitrile (IDPN)-induced dyskinetic syndrome in mice: antagonism by the calcium channel antagonist nifedipine

Chronic administration of IDPN leads to the development of a persistent syndrome which is characterized by lateral and vertical neck dyskinesias, random circling behaviors, and locomotor hyperactivity. Although the dihydropyridine (DHP) calcium channel antagonist nifedipine inhibited all aspects of the syndrome, lateral head dyskinesias (laterocollis) and circling abnormalities were the most significantly affected signs. Dysregulation of calcium-dependent processes might be involved in the pathogenesis of the IDPN-induced dyskinetic abnormalities and clinical disorders of movement in humans.

Increased cortical serotonin-2 (5-HT-2) receptors in the iminodipropionitrile (IDPN)-model of persistent dyskinesia in the rat

Chronic treatment with IDPN causes a persistent behavioral syndrome which is reminiscent of the head shakes, backward locomotion, and hyperactivity observed after acute injection of 5-HT agonists in rodents. Evaluation of the characteristics of 5-HT receptors, using mianserin to label 5-HT-2 receptors, revealed a significant increase in the number of binding sites in the cortices of rats which demonstrated the IDPN-induced syndrome. There was an associated decrease in the affinity of the receptors. These results add more evidence to support the idea that the serotonergic system may play a significant role in the manifestation of the persistent abnormalities induced by IDPN.

Rat brain PCP receptors: alterations in binding parameters following chronic administration of opiate agonists and antagonists

Phencyclidine (PCP) is a widely abused drug of the arylcyclohexylamine class which is capable of producing symptoms of acute psychosis in man. PCP interacts with a specific CNS receptor, for which a putative endogenous peptide ligand has been identified. We have investigated whether PCP receptor binding parameters are modulated by activity in central opiate pathways. We have found that chronic administration of both an opiate agonist (etonitazene) and an opiate antagonist (naloxone) are able to decrease the affinity of the PCP receptor for TCP, a thienyl derivative of PCP. Furthermore, naloxone, but not etonitazene, resulted in a significant increase in the Bmax of TCP binding to the PCP receptor. These results suggest that neural activity mediated by CNS opioids systems is capable of affecting the binding parameters of the PCP receptor.