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The concentration of somatostatin-like immunoreactivity (SS-LI) was determined by radioimmunoassay in neocortical tissue resected from 20 patients with pharmacologically intractable complex partial seizures. Most resections included either the anterior temporal pole neocortex (15 cases) or cingulate gyrus neocortex (3 cases). The concentration of SS-LI was lowest in cortical tissue immediately adjacent to cortical tumors. Preoperative electrical recordings suggested that this tissue was the seizure focus. In vitro recordings showed that this tissue also exhibited abnormal hyperexcitable synaptic responses. Higher levels of SS-LI, similar to normal values previously reported in human cortex, were present in non-focal temporal neocortical tissue (resected from patients in whom the seizure focus was in the ipsilateral hippocampus) in which no hyperexcitable synaptic activity was present in vitro. The functional loss of inhibitory transmitters suggested by the low SS-LI levels might provide a theoretical basis for the hyperexcitability observed in vivo and in vitro.

The effects of haloperidol on striatal and prefrontal cortical extracellular fluid dopamine (DA) concentrations were examined in sham-operated control rats and in rats which had received partial lesions of their dopamine systems. In control rats haloperidol administration produced increases in extracellular fluid DA concentrations in both the striatum and prefrontal cortex. However, in rats which had been partially lesioned with intracerebroventricular 6-hydroxydopamine, haloperidol produced an increase in extracellular fluid DA concentration in the prefrontal cortex but failed to alter striatal DA release. These data suggest that nigrostriatal and mesocortical DA neurons have different response capabilities following partial DA lesions.

The effects of exposure to acute mild footshock stress on concentrations of neurotensin-, somatostatin-, and corticotropin-releasing factor-like immunoreactivity (li) in mesotelencephalic dopamine system regions of the rat were examined. Mild stress exposure resulted in a selective and regionally specific increase in neurotensin-li concentrations in the ventral tegmental area (VTA), source of the dopaminergic innervation of the mesocortical and mesolimbic dopaminergic terminal fields. Concentrations of somatostatin- or corticotropin-releasing factor-li were not changed in any area examined. Levels of the dopamine metabolite, 3,4-dihydroxyphenylacetic acid, were increased only in the VTA and medial prefrontal cortex. These data suggest that neurotensin in the VTA may be involved in environmentally elicited activation of certain mesotelencephalic dopamine neurons.

Kyotorphin (Tyr-Arg) and its stable analogue [D-Arg]kyotorphin were injected into the substantia nigra of rats. Intranigral [D-Arg]-kyotorphin resulted in consistent ipsilateral rotational behavior which was naloxone-reversible. In comparison, intranigral Met-enkephalin induces naloxone-sensitive contralateral rotation. These results indicate a pharmacological effect of [D-Arg]kyotorphin in the substantia nigra that would appear to be independent of Met-enkephalin release.