Striatal met-enkephalin concentration increases following nigrostriatal denervation.

Following specific lesion of the nigrostriatal dopaminergic pathways in rat brain, striatal met-enkephalin on the lesioned side increased to 245% of that on the non-lesioned side. This increase was evident only after a lag period of 7 days and the increase was maintained for at least 2 months after lesion. By contrast, there was no change in striatal somatostatin or vasoactive intestinal polypeptide concentration, indicating that the effect was not a generalised one.

Evidence for a role of endogenous opioids in the nigrostriatal system: influence of naloxone and morphine on nigrostriatal dopaminergic supersensitivity.

The effects of morphine and naloxone on nigrostriatal function were evaluated by their influence on rotational behavior in rats with unilateral lesions of the substantial nigra. Two different rotational syndromes which result from different lesion placements, were examined. Rats with the contraversive syndrome, when given apomorphine, rotate away from the lesioned side, while rats with the ipsiversive syndrome rotate toward the lesioned side.

Altered characteristics of striatal [3H]ADTN binding following substantia nigra lesions.

The present experiments examined some characteristics of the enhanced striatal [3H]ADTN binding which occurs following substantia nigra lesion. The amount of binding of a fixed concentration of [3H]ADTN was greatly increased. The amount of guanine nucleotide sensitivity increased to an even greater extent than total [3H]ADTN binding.

Dopamine receptor sensitivity following nigrostriatal lesion in the aged rat.

This investigation sought to determine whether the ability to regulate dopamine receptor sensitivity following removal of dopaminergic innervation is altered during aging. Aged (24-26 months old) Fisher 344 rats compared with young (6 months old) rats had lower levels of dopamine and dopamine receptor binding ([3H]ADTN), but no change of dopamine-stimulated adenylate cyclase activity. Unilateral lesion of the nigrostriatal pathway produced equivalent dopaminergic denervation in rats of both age groups.