Pressor effects of acetylcholine microinjected into forebrain nuclei of unanesthetized rats

The injection of 13.5-54 nmol/500 nl of acetylcholine (ACH) into different brain areas of unanesthetized freely-moving 200-250 g male Wistar rats caused only pressor responses. In the prosencephalon, the lateral septal area was the site at which ACH was more effective, whereas injections into surrounding areas, such as the accubens/bed nucleus striae terminalis, the medial septal area or the lateral ventricle were less effective. No effective. No blood pressure effects were observed after injection into the anterior amygdala. In the diencephalon, the ventromedial hypothalamic nucleus was the most sensitive site, whereas injection of ACH into surrounding areas, such as the posterior and lateral hypothalamic or the dorsal and ventral prtemammillary nuclei was less effective. At all sites tested, the local pretreatment with 138-276 nmol atropine abolished the pressor response to ACH, suggesting a mediation through muscarinic receptors. The sites of injection were confirmed histologically. The present data indicate the existence of a cholinergic-sensitive site involved in the control of blood pressure at the level of the lateral septal area

Feeding behavior elicited by electrical stimulation of the lateral hypothalamic area in the rat: role of the adrenergic pathways and receptors.

To study the role played by neurotransmitters and their receptor mechanisms in the control of feeding behavior elicited by electrical stimulation, drugs that affect neurotransmission were injected via cannula electrodes into the lateral hypothalamic area. Pretreatment with noradrenaline (0.5 and 1.0 nmol) significantly increased the effect of hypothalamic stimulation on feeding, whereas injection of 1.0, 2.0 and 4.0 nmol of adrenaline or dopamine was ineffective. Phentolamine (40.0, 80.0 and 100.0 nmol) and propranolol (40.0, 80.0 and 120.0 nmol) induced a decrease in food intake, suggesting the involvement of both alpha and beta receptors in this mechanism. However, isoprenaline (20.0 nmol) also reduced food intake. Reduction of food intake by propranolol was probably related to the action of the local anesthetic. Alphamethyl-p-tyrosine (203.0 nmol), reserpine (32.8 nmol) and 6-hydroxydopamine (200.0 nmol) inhibited the feeding behavior elicited by electrical stimulation of the lateral hypothalamic area. These results suggest that electrical stimulation of the lateral hypothalamic area elicits feeding behavior by releasing noradrenaline. Alpha-adrenergic receptors seem to play a facilitatory role in feeding behavior.