No abstract

The two largest cells in a typical ganglion of the leech (Hirudo medicinalis) nervous system are the colossal cells of Retzius . These cells show a positive chromafftn reaction,

Injection of the serotonin neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), into the midbrain dorsal (DR) or median (MR) raphe nucleus of castrated and normal male rats was followed by measurement of serum luteinizing hormone (LH) level and the 5-hydroxytryptamine (5-HT) content of several hypothalamic and amygdaloid nuclei. Only the DR lesions lead to a significant decrease (42%) in serum LH level in normal rats. The elevated LH level in castrated animals was not affected by either lesion. The DR lesions were followed by 5-HT reductions only in the medial preoptic area, the arcuate and ventromedial hypothalamic nuclei, and in the basal and central amygdaloid nuclei. In contrast, the 5-HT reductions produced by MR lesions were much more widespread, being found in all nuclei assayed with the exception of the dorso- and ventromedial hypothalamic nuclei. In a second experiment, degeneration of serotonergic terminals in the ventromedial region of the hypothalamus following intradiencephalic injections of 5,7-DHT led to a significant decrease in serum LH level and a 5-HT reduction in the arcuate, ventromedial and dorsomedial hypothalamic nuclei. 5,7-DHT injections into the medial preoptic area and the anterior hypothalamic area did not affect serum LH level. These results suggest that a serotonergic pathway originating in the midbrain dorsal raphe nucleus and innervating the mediobasal hypothalamus has a stimulatory influence on LH secretion.

The requirement of using homologous antisera (primary antiserum and peroxidase-antiperoxidase (PAP) complex raised in the same species) in the unlabeled antibody enzyme method has been investigated at the light and electron microscopic level using the localization of insulin, glucagon and growth hormone as model systems. Optimum immunocytochemical staining for all three antigens was observed when sheep or goat antirabbit gamma-globulin (S-ARgammaG or G-ARgammaG) were used to couple rabbit peroxidase-antiperoxidase complex with either guinea pig antisera to insulin (GP-AIS) or glucagon (GP-AGS), or monkey antisera to rat growth hormone (M-ARGH). The cross-reactivity between S-ARgammaG or G-ARgammaG and immunoglobulins in these primary antisera were substantiated by immunoelectrophoresis and radioimmunoassay. S-ARgammaG was shown to produce precipitation arcs with GP-AIS and M-ARGH that were similar to those seen when the latter were reacted with rabbit antiguinea pig gamma-globulin antiserum and goat antimonkey gamma-globulin antiserum, respectively. Radioimmunoassay results revealed that immunoprecipitation of 6-10% as compared to homologous antisera controls yielded excellent staining localization when S-ARgammaG was used for immunocytochemistry. Thus, heterologous antisera (primary antiserum and PAP complex raised in different species) may be used in the unlabeled antibody enzyme method as long as the coupling antiserum shows cross-reactivity with immunoglobulins of the primary antiserum and the PAP complex.