strychnine and Tachycardia

We have previously reported that stimulation of the hypothalamic arcuate nucleus (ARCN) by microinjections of N-methyl-d-aspartic acid (NMDA) elicits tachycardia, which is partially mediated via inhibition of vagal inputs to the heart. The neuronal pools and neurotransmitters in them mediating tachycardia elicited from the ARCN have not been identified. We tested the hypothesis that the tachycardia elicited from the ARCN may be mediated by inhibitory neurotransmitters in the nucleus ambiguus (nAmb). Experiments were done in urethane-anesthetized, artificially ventilated, male Wistar rats. In separate groups of rats, unilateral and bilateral microinjections of muscimol (1 mM), gabazine (0.01 mM), and strychnine (0.5 mM) into the nAmb significantly attenuated tachycardia elicited by unilateral microinjections of NMDA (10 mM) into the ARCN. Histological examination of the brains showed that the microinjections sites were within the targeted nuclei. Retrograde anatomic tracing from the nAmb revealed direct bilateral projections from the ARCN and hypothalamic paraventricular nucleus to the nAmb. The results of the present study suggest that tachycardia elicited by stimulation of the ARCN by microinjections of NMDA is mediated via GABAA and glycine receptors located in the nAmb.

Topics: Animals; Arcuate Nucleus of Hypothalamus; GABA Antagonists; GABA-A Receptor Agonists; Glycine Agents; Heart; Male; Medulla Oblongata; Microinjections; Muscimol; N-Methylaspartate; Pyridazines; Rats, Wistar; Receptors, GABA-A; Receptors, Glycine; Stimulation, Chemical; Strychnine; Tachycardia

In general, Adie's syndrome does not represent a serious diagnostic problem. In cases of cerebrospinal syphilis the Argyll-Robertson phenomenon or even absolute pupillary rigidity will be observed. Positive syphilis reactions will clarify these cases. The erroneous diagnosis of brain tumour may arise because of anisocoria. However, if pupillotonia can be ascertained by means of conjunctival instillation of drugs no further invasive diagnostics will be necessary. In some cases of Adie's syndrome concomitant emotional instability may be present. This dysautonomic reaction type of personality will hardly ever be confounded with the psychological disturbances encountered in brain tumours. Therapy is restricted to symptomatic measures. Pupillotonia can be influenced by strychnine and thymoxamine. Headache and facial neuralgia respond to the usual therapeutic schemes. Sweating disorder cannot be influenced. Neuropharmacological treatment may become necessary in periods of acute emotional disturbance.

Topics: Adie Syndrome; Diagnosis, Differential; Fludrocortisone; Humans; Neurosyphilis; Neurotic Disorders; Reflex, Pupillary; Strychnine; Sympatholytics; Tachycardia

Topics: Alkaloids; Animals; Cardiovascular System; Hypertension; Mice; Neuromuscular Depolarizing Agents; Neuromuscular Nondepolarizing Agents; Plant Extracts; Rats; Respiratory System; Strychnine; Tachycardia