Infusions into the oculomotor nucleus or nerve: a method of estimating the dosage at which transmitter antagonists infused intracranially produce nonspecific blocking of neural activity

Regional neuroleptic microinjections indicate a role for nucleus accumbens in lateral hypothalamic self-stimulation reward

Bilateral microinjections of the neuroleptic, cis-flupenthixol, were made into 56 forebrain targets distributed across various dopamine (DA) terminal fields in the forebrain. Drug effects on medial forebrain bundle (MFB) stimulation-produced reward were assessed with a rate-frequency procedure implemented in a runway paradigm in a discrete-trial fashion. This method generated independent measures of drug-induced changes in the MFB stimulation reward and operant motor/performance capacity. Control experiments were run with the inactive isomer, trans-flupenthixol. Results indicate a major role for accumbens DA in MFB reward, but not for the DA in caudate and medial frontal cortex. Few drug-induced motor/performance deficits were found at any site. In 14 selected subjects, 6-OHDA-induced chronic DA lesions were made at the same site as neuroleptic microinjection. These results confirmed the reward effects of acute DA receptor blockade, but produced a greater associated motor/performance impairment. Both behavioral effects of the lesion recovered within 2 weeks in many, but not all subjects.

Reserpine-induced rigidity in rats: drug effects on muscle tone from corpus striatum and nucleus accumbens

A study of the pathophysiological mechanisms of reserpine rigidity with the aid of a mechanographic method for the quantification of muscle tone. Apomorphine was used as a test substance to reduce reserpine rigidity by stimulation of dopamine receptors. Some experiments were made with additional drug treatment in an attempt to ascertain the dopaminergic specificity of the test. Apomorphine injected bilaterally to the corpus striatum has been shown to counteract the rigidity [6]. Microinjections of reserpine to corpus striatum induced rigidity with dominance in the hindleg ipsilateral to the side of injection. This rigidity was reduced by subcutaneous apomorphine. The effect of subcutaneous apomorphine on the rigidity was blocked by prior microinjection of trifluoperazine to the corpus striatum. Injections to nucleus accumbens were ineffective in all these respects. It is concluded that reserpine induces rigidity mainly by interference with the dopamine transmission in the corpus striatum.

The inhibitory modulation of agonistic behavior in the rat brain: a review

Neural regions which exercise an inhibitory influence on agonistic behavior are identified by the enhancement of agonistic behavior that follows their removal. The specific kinds of agonistic behaviors altered by each region are then examined. Increased reactivity to the experimenter and enhanced shock-induced fighting are produced by lesions of the region ventral to the anterior septum, the lateral septum, the medial hypothalamus, and the dorsal and median raphe nuclei. It is argued that the increased reactivity and shock-induced fighting correspond to an enhancement of defensive behavior. Mouse killing is induced by lesions of the anterior olfactory nucleus, the region ventral to the anterior septum, the lateral septum, the medial hypothalamus, the dorsal and median raphe nuclei, and the medial amygdala. Because the lesion-induced mouse killing is similar to that emitted by spontaneous mouse killers, it is argued that these regions normally exert an inhibitory control over predatory killing. The available evidence on social attack behavior has not convincingly identified regions exerting an inhibitory control over this dimension of behavior. Our conclusion is that separate brain systems exert an inhibitory control over defensive behavior, predatory killing, and social attack behavior. To a substantial extent, the regions modulating these behaviors appear to act independently of one another. The only neurotransmitter that is clearly active in these inhibitory systems is serotonin, and has only been directly implicated in the control of mouse killing by neurons originating in the dorsal and median raphe nuclei.