The coexistence of cholecystokinin- and tyrosine hydroxylase-like immunoreactivities within neurons of the rat ventral mesencephalon was analyzed by using an indirect immunofluorescence technique for the simultaneous demonstration of two antigens in the same tissue section. A high degree of colocalization was observed in the substantia nigra pars compacta, in which 80-90% of all labeled neurons at rostral and up to 70% at intermediate levels contained both cholecystokinin and tyrosine hydroxylase. At caudal levels, the incidence of colocalization declined to approximately 30-50%. All of the immunoreactive perikarya in the substantia nigra pars lateralis were labeled with both substances. Other areas of the ventral midbrain that exhibited a moderate proportion of neurons immunoreactive for both cholecystokinin and tyrosine hydroxylase included the ventral tegmental area, interfascicular nucleus, and rostral and caudal linear nuclei. In addition, coexistence was occasionally observed within neurons of the central and ventral periaqueductal gray matter, supramammillary region, peripeduncular region, retrorubral field, and extremely rarely, within the substantia nigra pars reticulata. Cell bodies containing tyrosine hydroxylase-like immunoreactivity (indicative of dopamine) usually outnumbered those containing the peptide except in the supramammillary region and in the ventral periaqueductal gray matter, where the cholecystokinin perikarya were present in higher numbers. The double-labeling colocalization technique was combined with fluorescence retrograde tracing to determine some of the forebrain projections of these neurons. Ventral midbrain neurons containing both cholecystokinin and tyrosine hydroxylase were found to project to the caudate-putamen, nucleus-accumbens, prefrontal cortex, and amygdala. These projections originated from neurons located predominantly in the substantia nigra pars compacta and the ventral tegmental area. Thus, cholecystokinin occurs within the well-known dopaminergic nigrostriatal pathway in the rat. Overall, these results demonstrate that a significant proportion of the dopamine neurons giving rise to the ascending mesotelencephalic projections also contain the peptide cholecystokinin.

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The first-line recommended treatment for stable paroxysmal supraventricular tachycardia (PSVT) is the use of vagal maneuvers. Often the Valsalva maneuver is conducted. We describe two patients who converted to sinus rhythm without complications, using a head down deep breathing (HDDB) technique.

A 54-year-old woman with insulin-requiring type 2 diabetes mellitus presented with acute shortness of breath and drowsiness on a background of polydipsia, weakness and significant weight loss. One year ago, she had decided to stop her insulin and other medications and adopt lifestyle modifications instead. Initial emergency department (ED) blood samples were highly lipaemic and appeared strawberry pink. She was eventually diagnosed with diabetic ketoacidosis (DKA) with severe hypertriglyceridaemia, intubated for airway protection, and managed with fluid resuscitation and intravenous insulin to good effect. We share an uncommon DKA presentation at the ED. History was limited as the patient was drowsy and minimally communicative. Physical examination was unremarkable. Blood investigations were also delayed in view of the need for additional centrifugation. These contributed to a paucity of information in the acute setting and resulted in a diagnostic challenge.

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